Home General Knowledge GENERAL SCIENCE : BIOLOGY
Friday, 24 February 2012 03:53





Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment.

Food Chain & Food Web

A food chain is the sequence of who eats whom in a biological community (an ecosystem) to obtain nutrition. A food web (or food cycle) is interconnected food chains depicting feeding connections (what eats what) in an ecological community.

Trophic Levels:

The trophic level of an organism is the position it holds in a food chain.

1. Producers (organisms that make their own food from sunlight and/or chemical energy from deep sea vents) are the base of every food chain these organisms are called autotrophs

2. Primary consumers are animals that eat producers; they are also called herbivores (plant-eaters).

3. Secondary consumers Eat primary consumers. They are carnivores (meat-eaters) and omnivores (animals that eat both animals and plants).

4. Tertiary consumers eat secondary consumers.

Quaternary consumers eat tertiary consumers.

6. Food Chains “end” with top predators, animals that have little or no natural enemies.

When any organism dies, it is eventually eaten by detrivores (like vultures, worms and crabs) and broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.

The energy is transferred from one stage to other through this chain and the total energy declares as it moves from producers to different levels of consumers because of utilization by the species. So it can be represented by a pyramid which tapers towards each level of consumers.

Biota: The plants and animals of a specific region or period, or the total aggregation of organisms in the biosphere.

Community: Any grouping of populations of different organisms that live together in a particular environment.

Ecosystem: A discrete unit, or community of organisms and their physical environment (living and non-living parts), that interact to form a stable system.

Endemic: A species or taxonomic group that is restricted to a particular geographic areas because of such factors as isolation or response to soil or climatic condition; this species is said to be endemic to the place and would be native.

Habitat: The place, including physical and biotic conditions, where a plant or an animal usually occurs.

Niche: The role the species plays in the functioning of the ecosystem: the “functional status of an organism in its community”.

Population: A group of potentially inter breeding individuals of the same species found in the same place at the same time.

Species: A group of organisms formally recognized as distinct from other group; the taxon rank in the hierarchy of biological classification below that of genus; the basic unit of biological classification, usually defined by the reproductive isolation of the group from all other groups of organisms.


Organic evolution is the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms. Evolution is any change across successive generations in the heritable characteristics of biological populations.

Abiogenesis or biopoesis is the study of how biological life arises from inorganic matter through natural processes, and the method by which life on Earth arose. The RNA world hypothesis proposes that life based on ribonucleic acid (RNA) pre-dates the current world of life based on deoxyribonucleic acid (DNA), RNA and proteins. RNA is able both to store genetic information, like DNA, and to catalyze chemical reactions, like an enzymeprotein. It may therefore have supported pre-cellular life and been a major step in the evolution of cellular life.

Theories of Evolution


The theory of evolution as put forth by French biologist Lamarck has come to be known as Lamarckism. The theory has two salient features.

Use and Disuse of Parts: According to Lamarck, continuous use of a part results in it being well developed and disuse of a part over a long period of time will result in its degeneration. For example, giraffes where forced to extend their necks and stretch their legs to reach higher vegetation over a period of time. This resulted in every generation having a little longer neck and legs than the previous one. Webbed feet in aquatic birds and thought to have developed due to constant spreading of toes and the stretching of the skin between. Flatfish also are thought to have developed their shape due to lying on their sides in shallow water.

Inheritance of Acquired Characters: According to Lamarck, the characters that an organism acquired due to a change in their environment such as long neck, webbed feet, flat bodies, etc. were passed on to the next generation. In this way, evolution from simpler to complex forms took place.

However, this theory was not widely accepted as it is know that acquired characters are only phenotypic changes and not genotypic. Thus, while the cases of giraffe, aquatic birds and flatfish do show that evolution has occurred, Lamarckism does not provide a satisfactory answer to the mystery of evolution.


The theory of natural selection was put forth by Charles Darwin in his book on the Origin of Species by Means of Natural Selection co-authored by Alfred Russel Wallace. According to Darwin, nature has its own ways of selecting the best from the available species for continuation of life. The mechanism of natural selection works as follows:

(a) Individuals of a species produce more offspring than necessary to replace themselves.

(b) This result in competition and struggle for existence among the individuals. Within the specious itself there is variation that results in minor differences between the individuals.

(c) Thus in the struggle for existence only the ones with the variations best adapted to their environment survive.

(d) In this manner nature ensures survival of the fittest.

Study of fossils is called Palaeontology. Fossils are defined as preserved remains of a living organism that existed on earth a long time ago. Fossils are formed by the preservation of the remains of the organisms that existed in the earlier days. The dead bodies of the organisms are immediately covered by materials which do not allow decomposition at a fast rate. This preserves the dead bodies which form fossils. For example, we know of the existence of dinosaurs only through fossils.

In addition to knowledge about the extinct forms, fossils also provide links between two groups indicating that perhaps one species evolved from the other. For example, a fossil called archaeopteryx show features of both reptiles (teeth) and birds (wings).

The comparative anatomical studies of various types of organisms shows structural and functional differences and similarities between various species. For example, the basic structure of all the flowers is the same with the whorls of calyx, corolla, androecium and gynoecium. However, each species is different in the shape, size and number of the individual members of the species. Similarly, the limb-bone pattern of all the animals with four limbs (tetrapods) in the same pentadactyl limb.

Such organs that have a common basic form but are present in different species are called the homologous organs. Thus the wings of bat are homologous to the limbs of man.

Analogous Structure: There appear to be many structures that are similar because of the function they carry out and in their external appearance. However, these structures differ internally. Such structures are called analogous structure. For example, wings of bat and butterfly are similar in appearance and function but they are internally very different and have different origins. Similarly thorns and spines seen in plants are also analogous structures. Both are pointed structure that are protective in function. However, thorn is modification of stem and spine is modified leaf. Another example of analogous structures in plants are the tendrils of different types carrying out similarly function.

Living Fossils: The study of morphology also reveals some organisms that form links between two different groups. This is further evidence that evolution has taken place and it also shows the direction taken by the process of evolution. These organisms that show the features of two different groups are called the living fossils as they provide a link between the two groups. They are as important as fossils in providing linkages and also they may have been surveying without much variation for many years.

For example, some living fossils are:

Duck-billed platypus, an egg laying mammal that forms a link between reptiles and mammals; amphibians that show link between fishes and reptiles; lungfish that shows link between amphibians and fishes.


Taxonomy: is scientific classification and nomenclature of organisms. Modern biological classification has its root in the work of Carolus Linnaeus, who grouped species according to shared physical characteristics. He introduced Binomial Nomenclature, or naming with two parts Genus and Species.

The classification of living things into animals and plants is an ancient one. Aristotle (384-322 BC) classified animal species in his work The History of Animals, and his pupil Theophrastus (c. 371-c, 287BC) wrote a parallel work on plants Historia Planation (The History of Plants).

Carolus Linnaeus (1707-1778) laid the foundations for modern biological nomenclature, now regulated by the No- menclature Codes. He distinguished two kingdoms of living things: Regnum Animale (‘animal kingdom’) for animals and Regnum Vegetable (‘vegetable kingdom’) for plants.

In 1674, Antonie van Leeuwenhoek, often called the “father of microscopy”, sent the Royal Society of London a copy of his first observations of microscopic single-celled organism. Initially these were classified into plants and animals based on characteristics, later they were made into a single kingdom Protista based on based on proposal by Richard Owen and John Hogg, Ernst Haeckel.

The development of microscopy, and the electron microscope in particular, revealed an important distinction between those unicellular organisms whose cells do not have a distinct nucleus, prokaryotes, and those unicellular and multicellular organisms whose cells do have a distinct nucleus, eukaryotes. Now Protista was kingdom for Prokaryotes and Monera for Eukaryotes.

Robert Whittaker recognized and additional kingdom for the Fungi. The resulting five kingdom system, proposed in 1969 by Whittaker, has become a popular standard and with some refinement is still used in many works and forms the basis for new multi-kingdom systems. It is based mainly on differences in nutrition; his Plantae were mostly multicellular autotrophs, his Animalia multicellular heterotrophs, and his Fungi multicellular saprotrophs. The remaining two kingdoms, Protista and Monera, included unicellular and simple cellular colonies.






Small, simple single prokaryotic cell (nucleus is not enclosed by a membrane); some form chains or mats

Absorb food and/or photosynthesize

Bacteria, blue-green algae, and spirochetes


Large, single eukaryotic cell (nucleus is enclosed by a membrane); some form chains or colonies

Absorb, ingest, and/or photosynthesize food

Protozoans and algae of various types


Multicellular filamentous form with specialized eukaryotic cells

Absorb food

Funguses, molds mushrooms, yeasts, mildews, and smuts


Multicellular form with specialized eukaryotic cells; do not have their own means of locomotion

Photosynthesize food

Mosses, ferns, woody and non-woody flowering plants


Multicellular form with specialized eukaryotic cells; have their own means of locomotion

Ingest food

Sponges, worms, insects, fish, amphibians, reptiles, birds, and mammals

The original plant kingdom proposed by Linnaeus and subsequent taxonomists of that period included the bacteria, fungi, algae, liverworts, mosses, ferns, conifers and flowering plants. Plants in general and considered to exhibit the following distinguishing characters.

(a) Plants exhibit a great deal of variation in their form and size. Plant body is usually asymmetrical. However, in higher plants structures like leaves and flowers have a definite form and shape.

(b) Plants are rooted mostly and as such are incapable of locomotion. However, certain localized movements may occur in a plant body.

(c) Plants exhibit unlimited growth, almost throughout their life span.

(d) Absence of locomotion.

(e) Plants exhibit largely autotrophic nutrition or saprotrophic nutrition. Particulate matter cannot be absorbed and only materials present in a solution state can be absorbed.

(f) Plant body is composed of cells which have a distinct cell wall, a vacuole filled with sap and plastids of different kinds. The cells do not have centrioles and lysosomes.

(g) Plant cells can synthesize all the amino acids, coenzymes and vitamins necessary for its functions.

Plants have reserve food as starch.

Kingdom Animalia

The original Animal Kingdom proposed by Linnaeus included the protozoans, sponges, jelly fishes, worms, crabs, insects, spiders, snails, starfishes, sharks, bony fishes, frogs, lizards, birds and mammals. In general, animals exhibit the following distinguishing characters.

(a) The animal body generally exhibits a definite symmetry, form and shape.

(b) Animals have the capacity to move from place to place in search of their necessities.

(c) Growth in animals is determined and occurs proportionately in all parts of the body.

(d) Animals are generally heterotrophic, obtaining their food from plants and other animals.

(e) Animals have the property of irritability – the capacity to respond to a stimulus.

(f) The cells, which form an animal’s body do not have a cell wall. Plastids and vacuoles are generally absent and centrioles & lysosomes are present.

(g) Animal cells cannot synthesize all the necessary amino acids, vitamins and coenzymes and as such will have to obtain them from external sources.

(h) Reserve food is glycogen.

Approximately 2000 million years ago, the first animal appeared in the waters of the earth. Since then, millions of animals have evolved from simpler ones.

They have been classified by scientists according to their complexity.


The simplest and probably the first animals were the single-celled protozoans.

Examples: phylum protozoa.

Characteristic of Phylum Protozoa

1. Single-celled microscopic animals.

2. Live in fresh water, sea and soil.

3. Parts of the cell, known as organelles carry out metabolic functions.

4. May be free-living or parasitic (cause disease in the host).

Types of protozoans

1. Flagellate: These locomote by means of whip-like processes called flagella.

Example: Trypanosoma

2. Ciliates: These locomote by means of a large number of fine hair like cilia.

Example: Paramoecium.

3. Rhizopida: These have no definite shape. They extend their jelly like body in any direction (pseudopodia) to engulf food or to move.

Example: Amoeba, Entamoeba hystolitica (causes amoebic dysentery).

4. Sporozoans: Spore producing, internal parasites with complex life cycles. A generation reproducing sexually may give rise to an asexual generation in a different host.

Example: Plasmodium (causes malaria).


Animals other than protozoans are made up of groups of cells that become specialized to perform specific functions for the entire organism.

Cellular level

The simplest multicellular animals are communities of colonies of cells growing in simple or branched forms. The cells of the colony are embedded in a common protoplasmic mass but remain functionally independent of each other and is capable of regenerating from single cell.

Example: Phylum Porifera.

Characteristic of Phylum Porifera

  1. Animals with cellular organisation.
  2. Mostly marine, but a few live in fresh water.
  3. Remain stationary, attached to underwater rocks, coral reefs, water plants, crabs and molluscs.
  4. Variously shaped, often giving out finger-like branches.
  5. Body consists of a hollow tube with numerous pores through which water (along with food) is drawn into the body. Digestion is intracellular.
  6. A network of canals composed of cells which contain tiny needle like formations of silica (spicules) form the internal support system or support is provided by sponging, a framework of elastic fibres.
  7. Reproduction may be sexual or asexual by budding.

Examples: Sycon, Bath sponge.


Closer to the mainstream of evolution are the animals with cells organised into two definite layers. The inner layer encloses a body cavity. They are also the simplest animals to have a nervous system and gut.

Examples: Phylum Coelenterata (Cnidaria).

Characteristics of Phylum Coelenterata

(1) Two-layered body, which is radially symmetrical.

(2) Generally marine, but a few species are fresh water.

(3) Inner layer encloses a body cavity called gastro vascular cavity. It opens at one end, which serves as the mouth and anus.

(4) Outer layer has tentacles and is armed with stinging cells called nematocysts which can inject venom. It helps in feeding as well as in escaping from enemies.

(5) Between the ectoderm and the endoderm is a non-cellular gelatinous layer called mesoglea.

(6) Reproduction is asexual as well as sexual.

(7) Life-cycle consists of a fixed (polyp) generation alternating with a swimming (medusa) generation.

Examples: Sea anemones, Corals, Hydra, Portuguese man of war and Jellyfish.


Next in the evolutionary ladder are animals with a three-layered body wall.

Acoelomata: The simplest among the triploblasts are the soft bodied worms. These have no true body cavity, respiratory system or blood. They possess a rudimentary nervous system. The mesoderm forms muscles, reproductive organs, and a type of connective tissue called parenchyma, which fills up the body cavity. Hence, there is no true coelom.

Examples: Phylum Platyhelminthes (Flat worm); and Phylum Nemathelminthes (Nematoda).

Characteristics of Phylum Platyhelminthes

(1) These are the simplest triploblasts showing bilateral symmetry.

(2) Some are free-living found in water or damp soil. Others are parasitic.

(3) They are flat, unsegmented worms.

(4) Body cavity between body wall and digestive tract absent.

(5) The alimentary canal has only one opening, which serves as the mouth and anus.

(6) Generally, hermaphrodites i.e. each individual possesses the male and female reproductive organs.

Examples: Planaria: Free living in water;

Liver fluke: Parasites in the human intestines. It lacks a digestive tract.

Characteristics of Phylum Nemathelminthes

(1) Triploblastic body shows bilateral symmetry.

(2) Free living or parasitic.

(3) Possess long, smooth, cylindrical unsegmented body.

(4) False body cavity present.

(5) Alimentary canal passes through the body from the mouth to anus.

Examples: Hook worm and Ascaris: Parasites in man.

Eelworm: Potato parasite

Hairworm: Larvae are internal parasites of insects and crustaceans while the adult is free-living

Wuchereria bancrofti: Parasite, causes filarial in humans.

Coelomata: The next branch in the evolutionary ladder, occupied by triploblasts with a true body cavity.

Characteristics of Phylum Annelida

Segmentation is a comparatively advanced feature shared by annelids and arthropods (insects, spiders).

(1) Triploblastic with bilaterally symmetrical bodies.

(2) Body is soft and segmented.

(3) True body cavity is present.

(4) Organs of excretion (nephridia) are segmentally arranged in the coelom.

(5) Body is covered by a non-chitinous cuticle, which may have chitinous setae formed by the epidermis.

(6) A majority of annelids are hermaphrodites.

(7) Reproduction is generally sexual, but some may reproduce asexually by regeneration.

Characteristics of Phylum Arthropoda

This is the largest phylum and nearly 80% of the animal kingdom belong to this phylum.

(1) The body is bilaterally symmetrical, segmented and divided into head, thorax and abdomen.

(2) A characteristic feature is the presence of jointed legs or appendages, which may be variously modified.

(3) The soft body is protected by a hard, chitinous, inelastic exoskeleton.

(4) To enable growth, the exoskeleton is periodically shed by a process called moulting or ecdysis.

(5) To allow free movement of parts, the exoskeleton as a number of joints with thin flexible membrane.

Arthropods are divided into four classes.


(a) These are mostly aquatic.

(b) The head and thorax are fused.

(c) Two pairs of antennae (feelers) are present.

(d) One pair of jaw is present.

(e) Several jointed appendages are present throughout the body to perform functions like locomotion (walking, swimming) and feeding.

Examples: Crabs, crayfishes, prawns, water-fleas, lobsters, shrimps, Cyclops (fresh water crustacean).


(a) The body has numerous segments.

(b) Each segment bears one or two pairs of limbs

(c) The head bears a pair of short antennae.

Examples: centipede, millipede


(a) The body is divided into distinct head, thorax and abdomen.

(b) The thorax bears three pairs of legs

(c) Two pairs of wings are generally present

Examples: Housefly, mosquito, grasshopper, butterfly, beetle, cockroach, locust, bees, ants, silver fish.

Note: exception among Insects

Housefly: Only one pair of wings

Head louse: Wings are absent


(a) Head and thorax fused to form the anterior (front) part of the body. Abdomen forms the posterior part of the body.

(b) Four pairs of legs are present.

(c) Wings and antennae are absent

Examples: ticks, mites, spider, scorpion

Characteristics of Phylum Mollusc

The molluscs have no close relatives and they constitute the teeming life forms of the fresh and marine waters.

(1) Their soft bodies are usually supported by a hard shell composed of calcium carbonate.

(2) They breathe through gills, Land molluscs have lungs.

(3) Muscular foot helps in locomotion.

Examples: snails, slugs, clams, oysters, mussels, squids, octopus, cuttle fish, mollusc

Characteristics of Phylum Echindermata

(1) These are marine animals with radially symmetrical bodies.

(2) They have a spiny exoskeleton.

(3) Their unsegmented body is characterized by the absence of head and presence of five regularly arranged arms.

(4) Locomotion is brought about by means of tube feet.

Examples: starfish, brittle-star, seaurchin, sea cucumber.

Characteristics of Phylum Chrodata

Members of the phylum chrodata are characterised by three unique features, at least during the early stages of their development. They show the presence of:

(1) A rod-like structure called notochord lying above the digestive tract.

(2) A tubular nerve cord lying above the notochord.

(3) Paired gill slits in the phrangeal region.

Of these, only the nerve cord persists throughout the life of the organism. The notochord may be replaced by a vertebral column and the gill slits disappear completely during the embryonic stage. A majority of the chordates belong to the sub-phylum Vertebrata, which is further divided into five major classes.


This class, with 20,000 living species out number all other vertebrates. The chief characteristics of the class are:

(a) Aquatic habitat.

(b) Streamlined body. The spindle shaped body (neck absent) is an adaptation to its aquatic environment.

(c) Cold-blooded, i.e. their body temperature fluctuates with outside temperature.

(d) Scaly exoskeleton. Body is covered by overlapping scales.

(e) Gills are the organs of respiration.

(f) Fins (modified limbs) are the organs of locomotion.

(g) Heart is two chambered.

(h) External ears and eyelids are absent.

(i) Nostrils have no respiratory function.

(j) Fishes are oviparous, i.e. they lay eggs.

Examples: sharks, skates, carps, pomfrets, sardines, herrings, trouts, dog-fishes.


They can live on land, but begin their life in the water.

Their chief characteristics are:

(a) Aquatic and terrestrial habitat. Larvae stage is aquatic. Adult can live on land and in water.

(b) Cold-blooded.

(c) Smooth, slimy, non-scaly exoskeleton, adapted to play a respiratory role.

(d) Lungs are the main organs of respiration in the adult. Larvae breathe through gills.

(e) Five fingered (penta-dactyl) limbs are the organs of locomotion. Nails and claws are absent.

(f) Heart is three chambered.

(g) External ear is absent.

(h) Amphibians are oviparous.

Examples: frog, toad, newt, salamander


The reptiles were the first of the four legged fishes to make a total conquest of the land.

The general characteristics of reptiles are as follows:

(a) Terrestrial habitat.

(b) Cold blooded.

(c) Body covered by a water proof scaly exoskeleton.

(d) They respire through lungs.

(e) Digits of the limbs have claws for protection.

(f) Heart is three-chambered.

(g) Ear drum is depressed.

(h) Distinct neck is present.

(i) Reptiles are oviparous.

Examples: lizards, snakes, crocodiles, alligators, turtles, tortoises.

Note: Exceptions among Reptilia Crocodiles and Alligators: Four chambered heart.


Birds are the descendents of reptiles

The general characteristics of birds are:

(a) Arboreal habitat, i.e. they inhabit or live on trees.

(b) They are warm-blooded.

(c) They have a feathery exoskeleton.

(d) Lungs have membranous extensions called air sacs.

(e) The fore-limbs are modified into wings.

(f) Heart is four-chambered.

(g) Bones are light and hollow.

(h) A distinct, flexible neck region is present.

(i) Teeth absent, ears internal.

(j) Birds are oviparous.

Examples: Penguins, ostrich, kivis, pigeon, crow, swallow, magpie, duck, crane, eagle.


Mammals are the most active and flexible in their response to the environment. The general characteristics of mammals are:

(a) Habitat may be aquatic, terrestrial or arboreal.

(b) Warm-blooded.

(c) Hairy exoskeleton acts as an insulating layer. In aquatic mammals, where hair is negligible, a subcutaneous layer of fat provides insulation.

(d) Lungs are the organs of respiration.

(e) A muscular diaphragm separates the thoracic cavity from the abdomen.

(f) Skin has sweat glands for regulation of body temperature and sebaceous glands, which secrete an oily substance to keep the skin water proof.

(g) Heart is four chambered.

(h) Teeth are embedded in sockets.

(i) They have two sets of teeth temporary or milk teeth and the permanent teeth.

(j) Mature red blood cells do not have a nucleus.

(k) They have external ears called pinna.

(l) Males have copulatory organ called penis and the testes are located externally in scrotal sacs (except elephants and aquatic mammals).

(m) The anus and urinogenital openings are generally separate.

(n) Most mammals are viviparous, i.e. they give birth to young ones.

(o) The mother suckles her young ones on milk secreted by special glands called the mammary glands. In lower mammals, the mammary glands develop from the sweat glands while in higher mammals they are the modified sebaceous glands.

Mammals with higher brain (Primates)

  • They are predominantly arboreal and a return to land by some forms is secondary.
  • Their specialised characters include a large cranium with a highly developed brain, which accounts for their intelligence.
  • The sense organs are also well developed and hands are perfect.
  • Eyes face forward, allowing for stereoscopic vision, i.e. ability to perceive depth, which helps to guage distances between branches as they swing from the branch to another.
  • Limbs and fingers are also suited for arboreal life.

Examples: gibbon, orang-utan, gorilla, monkey, man.

Important groups of Mammals

1. Egg-laying mammals (Prototheria): These are of reptilian descent and exhibit characteristics of both reptiles and mammals. They lay eggs, but the young ones hatched from the eggs are fed on mother’s milk.

Examples: Spiny ant-eater, duckbilled platypus.

2. Pouched mammals (Marsupialia): They are viviparous, but the young are born in an immature state. Hence, they develop in a pouch or marsupium on the abdomen of the mother where they are fed on milk produced by true mammary glands having teats.

Examples: Kangaroo, koala bear.

3. Insect-eating mammals (Insect-ivora): Small, nocturnal mammals with sharp, pointed canines, which feed on insects.

Examples: hedgehog, mole

4. Gnawing mammals (Logomorpha and Rodentia): They have sharp incisors for gnawing. Canines are absent.

Examples: rabbits, hares, porcupines, beaver, squirrels.

5. Flying mammals (Chitoptera): These mammals can fly. Forelimbs are long with digits elongated to support a fold of membranous skin, which forms the wing. Hind limbs are weak and used for hanging upside down.

Examples: bat, flying fox.

6. Carnivorous mammals (Carnivorous): They are flesh-eating terrestrial or aquatic mammals with powerful jaws. Three pairs of incisors, large and sharp canines, muscular limbs and powerful claws are their main characteristics. Aquatic forms have digits joined by skin to form paddles.

Examples: Terrestrial: dogs, cats, wolves, foxes, tigers, lions Aquatic: seal, walrus, sea-lion.

7. Hoofed mammals (Ungulates): They have horny hoofs at the end of their digits and they walk on the tips of their digits. A number of digits may be reduced. They are generally large in size and herbivorous.

Examples: camel, ox, goat, giraffe, pig, horse, ass, rhinoceros.

8. Sea-living mammals (Cetecea): These are aquatic mammals with largely modified fish-like bodies. Hair, pinnae and scrotum and hind limbs are absent. A layer of fat under the skin (blubber) maintains body temperature. Fore-limb is modified into paddles. They are carnivorous and gregarious.

Examples: porpoise, dolphin, whale.

9. Mammals with trunks (Proboscidia): This is an isolated group consisting of the largest land animal the elephant. The skin is thick, hair is scanty, testes are internal. The nose and upper lip forms a long trunk or proboscis used for transporting food and water to the mouth. The upper incisors are elongated to form tusk of solid ivory. Canines and premolars are absent. Molars are present.

Examples: Indian elephant, African elephant.


The cell:

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The cell was discovered by Robert Hooke in 1665.

The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that all cells come from pre-existing cells, that vital functions of an organism occur within cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

In the living organisms there are two types of cellular organizations. If we look at very simple organisms like bacteria and blue-green algae, We will discover cells that have no defined nucleus, these are prokaryotes cells. The cells which have definite nucleus are known as eukaryote. But the things which both have in common is that there are compartments surrounded by some type of membranes. These are called cell membranes.

Cell Membranes:

It is like a plastic bag with some tiny holes that bag holds all of the cell pieces and fluids inside the cell and keeps foreign particles outside the cell. The holes are there to let some things move in and out of the cell. Compounds called proteins and phospholipids make up most of the cell membrance the phospholipids make the basic bag. The proteins are found around the holes and help move molecules in and out of the cell. Substances like CO2 and O2 can move across the cell membrances by a process called diffusion. Diffusion is a process of movements of substance from a region of high concentration to a region where its concentration is low. Water also obeys the law of diffusion. The movement of water molecules is called osmosis.


It is the fluid that fills a cell. Scientists used to call the fluid proto plasm cytoplasm contain many specialized cell called organ cells. Each of these organ cells performs a specific function for the cell. Cell organells: Organells are living part of the cell have definite shape, structure and functions. To keep their function different from each other these organelles use membranes bound little structure within themselves. Some of the important organells are:

(a) Endoplasmic reticulum: It is a network of tulsular membranes connected at one end to the nucleus and on the other to the plasma membranes. Endoplasmic reticular (ER) are two types:- rough endoplasmic reticular (RER) and Smooth endoplasmic reticulum (SER).

Functions of ER:

  • It forms the supporting skeleton frame work of the cell.
  • It provides a pathway for distribution of nuclear material.
  • It provides surface for various enzymatic reactions.

(b) Ribosomes: It synthesis protein, and ER sent these protein in various part of the cell. Whereas SER helps in the manufacture of fats. Functions of these proteins and fats;

  • Protein and fat (lipid) help in building the cell membranes. This process is known as membranes biogenesis.
  • Some other protein and fat functions as enzymes and hormones.
  • SER plays a crucial role in detoxifying many poisons and drugs.

(c) Golgi apparatus: It is found in most cell. It is another packaging organelle like the endoplasmic reticulum. It gathers simple molecules and combines them to make molecules that are more complex. It then takes those big molecules, packages them in vesicles and either stores them for faster use or sends them out of the cell. Other functions:

  • Its functions include the storage modifications and packaging of products in vesicles.
  • It is also the organ Elle that builds lysosomes (cells digestion machines).

(d) Lysosomes: It is a kind of waste disposal system of the cell. It helps to keep the cell clean by digesting any foreign material. Old organs cell end up in the lysosomes. When the cell gets damaged, lysosomes may burst and the enzymes digest their own cells. Therefore lysosomes are also known as the “suicide ways” of the cell.

(e) Mitochondria: It is known as the power house of the cell. The energy required for various chemical activities headed for life is released by mitochondria in the form of ATP (adenosine-triphosphate) molecules.

  • ATP is known as the energy currency of the cell. The body uses energy are stored in ATP for making new chemical compounds and for mechanical work.
  • Mitochondria are strange organells in the sense that they have their own DNA and ribosomes, therefore mitochondria are able to make their own protein.
  • Mitochondria is absent in bacteria and the red blood cells of mammals and higher animals.

(f) Centrioles: It is a micro-tubular structure; centrioles are concerned with cell division. It initiates cell division.

(g) Plastids: These are two types of plastids:- chromoplastes (colour plastides) and leucoplast (white or colourless plastids).

  • Chromoplast impart colour to flowers and fruits.


The nucleus has been described as the brain of the cell as it regulates all metabolic and hereditary activities of the cell. The shape, size and number of nucleus present in a cell is variable.

Some cells like mature red blood cells of mammals and the sieve tubes in plants contain no nucleus.

The nucleus has

1. Nuclear Membrane: It is a selectively permeable envelop like structure around the nuclear contents which separates   the nucleoplasm from the cytoplasm.

2. The Nucleoplasm: The space within the nuclear envelope is filled by a transparent semi-solid, granular round substance or matrix called the nucleoplasm.

3. The Nucleous: It is a dense spherical granule contained within the nucleus. Its size is related to the synthetic activity of the cell. The nucleolus stores all the proteins of the ribosomes.

4. Nuclear pore: The pores help in exchange of materials between nucleoplasm and cytoplasm. RNA and ribosomes leave the nucleus through these pores.

Cell Inclusions

A variety of soluble and insoluble chemical products accumulating within the cell due to metabolism. These are generally stored in vacuoles or granules.

Vacuoles: These are clear spaces present in the cytoplasm enclosed by a membrane called Tonoplast. These contain fluid called cell sap in which water soluble substances are found.

In animal cells, the vacuoles, if present, are small and temporary. They store glycogen and proteins.

In plant cells, vacuoles are large and permanent. They generally contain water, anthocyanins, alkaloids, fats, sugars and proteins. Vacuoles also help to maintain the osmotic pressure in a cell.

Cell Cycle:

The cell cycle, or cell division cycle, is an ordered set of events, culminating in cell growth and division into two daughter cells. Non-dividing cells not considered to be in the cell cycle. The stages, are G1-S-G2-M. The G1 stage stands for “GAP 1”. The S stage stands for “Synthesis”. This is the stage when DNA replication occurs. The G2 stage stands for “GAP 2”. The M stage stands for “mitosis”, and is when nuclear (chromosomes separate) and cytoplasmic (cytokinesis) division occur. Mitosis is further divided into 4 phases.

It is the series of events that takes place in a cell leading to its division and duplication (replication). In cells without a nucleus (eukaryotes), the cell cycle can be divided in three periods: interphase – during which the cell grows, accumulating nutrients needed for mitosis and duplicating its DNA – and the mitosis (M) phase, during which the cell splits itself into two distinct cells, often called “daughter cells” and the final phase, Cytokinesis, where the new cell is completely divided. The cell division cycle is a vital process by which a single celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed.

Mitosis is nuclear division plus cytokinesis, and produces two identical daughter cells during prophase, prometaphase, metaphase, anaphase, and telophase. Interphase is often included in discussions of mitosis, but interphase is technically not part of mitosis, but rather encompases stages G1, S, and G2 of the cell cycle.

Whilst the process of meiosis bears a number of similarities with the ‘life cycle’ cell division process of mitosis, it differs in two important respects:

  • The chromosomes in meiosis undergo a recombination which shuffles the genes producing a different genetic combination in each gamete, compared with the coexistence of each of the two separate pairs of each chromosome (one received from each parent) in each cell which results from mitosis.
  • The outcome of meiosis is four (genetically unique) haploid cells, compared with the two (genetically identical) diploid cells produced from mitosis.

Meiosis can be divided into two stages, Meiosis I & Meiosis II. In meiosis I, chromosomes in a diploid cell resegregate, producing four haploid daughter cells. It is this step in meiosis that generates genetic diversity.

Prokaryotic Cell Division

The usual method of prokaryote cell division is binary fission. The prokaryotic chromosome is a single DNA molecule that first replicates, then attaches each copy to a different part of the cell membrane. When the cell begins to pull apart, the replicate and original chromosomes are separated. Following cell splitting (cytokinesis), their are then two cells of identical genetic composition.

It is much simpler than the Mitosis in Eukaryotes.

Differences between Prokaryotic Cells & Eukaryotic Cells

Typical organisms

Typical size

Type of nucleus


RNA-/ protein-synthesis Ribosomes

Cytoplasmatic structure

Cell movement




Cell division


Bacteria, archaea

~1 - ~10 m

Nucleoid region;

No real nucleus

Circular (usually)

Coupled in cytoplasm

50S + 30S

Very few structures

Flagella made of flagellia



Usually single cells

Binary fission (Simple division)


Protists, fungi, plants, animals

~10 – 100 m (sperm cells, apart from the tail, are smaller)

Real nucleus with double membrane

Liner molecules (chromosomes) with histone proteins

RNA-synthesis inside the nucleusprotein synthesis in cytoplasm

60S + 40S

Highly structured by endo membranes and a cytoskelegon

Flagella and cilia containing microtubules; lamellipodia and filopodia containing actin

One to several thousand (though some lack mitochondria)

In algae and plants

Single cells, colonies, higher multicellular organisms with specialized cells

Mitosis (fission or budding) Meiosis

Differences Between Plant Cells and Animal Cells







Cell wall:

Plasma Membrane:


Animal Cell


Round (irregular shape)

Animal cells don’t have chloroplasts

One or more small vacuoles (much smaller than plant cells)

Present in all animal cells



Only cell membrane

Lysosomes occur in cytoplasm.

Plant Cell

It is very rare

Rectangular (fixed shape)

Pllant cells have chloroplasts because they make their own food

One, large central vacuole taking up 90% of cell volume

Only present in lower plant forms



Cell wall and a cell membrane

Lysosomes usually not evident

Stages of Mitosis

Interphase: The cell is engaged in metabolic activity and performing its prepare for mitosis (the next four phases that lead up to and include nuclear division). Chromosomes are not clearly discerned in the nucleus, although a dark spot called the nucleolus may be visible. The cell may contain a pair of centrioles (or microtubule organizing centers in plants) both of which are organizational sites for microtubules.

Prophase: Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle.

Prometaphase: The nuclear membrane dissolves, marking the beginning of prometaphase. Protein sattach to the centromeres creating the kinetochores. Micrrotubules attach at the kinetochores and the chromosomes begin moving.

Metaphase: Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.

Anaphase: The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.

Telophase: Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage.

Cytokinesis: In animal cells, cytokinesis results when a fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells, each with one nucleus. In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.

The phases of melosis I & II

Prophase I: DNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. Chromosomal condensation allows these to be viewed in the microscope. Note that the bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.

Prometaphase I: The nuclear membrane disappears. One kinetochore forms per chromosome rather than one per chromatid, and the chromosomes attached to spindle fibers begin to move.

Metaphase I: Bivalents, each composed of two chromosomes (four chromatids) align at the metaphase plate. The orientation is random, with either parental homologue on a side. This means that there is a 50-50 chance for the daughter cells to get either the mother’s or father’s homologue for each chromosome.

Anaphase I: Chiasmata separate. Chromosomes, each with two chromatids, move to separate poles. Each of the daughter cells is now haploid (23 chromosomes), but each chromosome has two chromatids.

Telophase I: Nuclear envelopes may reform, or the cell may quickly start meiosis II.

Cytokinesis: Analogous to mitosis where two complete daughter cells form.

Meiosis II: Meiosis II is similar to mitosis. However, there is no “S” phase. The chromatids of each chromosome are no longer identical because of recombination. Meiosis II separates the chromatids producing two daughter cells each with 23 chromosomes (haploid), and each chromosome has only one chromatid.


Genetics is a discipline of biology, is the science of genes, heredity, and variation in living organisms. Genetics deals with the molecular structure and function of genes, and gene behaviour in context of a cell or organism (e.g. dominance and epigenetics), patterns of inheritance from parent to offspring, and gene distribution, variation and change in populations. Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viruses and bacteria, through plants and domestic animals, to humans.

Modern genetics started with Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who studied the nature of inheritance in plants. In his paper “Versuche uber Pflanzenhybriden” (“Experiments on Plant Hybridization”), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brunn, Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically. Although this pattern of inheritance could only be observed for a few traits, Mendel’s work suggested that heredity was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios.

Mendel discovered that when crossing white flower and purple flower plants, in result is not a blend. Rather than being a mix of the two, the offspring was purple flowered. He then conceived the idea of heredity units, which he called “factors”, one of which is a recessive characteristic and the other dominant. Mendel said that factors, later called genes, normally occur in pairs in ordinary body cells, yet segregate during the formation of sex cells. Each member of the pair becomes part of the separate sex cell. The dominant gene, such as the purple flower in Mendel’s plants, will hide the recessive gene, the white flower. After Mendel self fertilized the F1 generation and obtained the 3:1 ratio, he correctly theorized that genes can be paired in three different ways for each trait: AA, aa, and Aa. The capital “A” represents the dominant factor and lowercase “a” represent the recessive. (The last combination listed above, Aa, will occur roughly twice as often as each of the other two, as it can be made in two different ways, Aa or aA).

Mendel stated that each individual has two factors for each trait, one from each parent. The two factors may or may not contain the same information. If the two factors are identical, the individual is called homozygous for the trait. If the two factors have different information, the individual is called hererozygous. The alternative forms of a factor are called alleles. The genotype of an individual is made up of the many allele it possesses. An individual’s physical appearance, or phenotype, is determined by its alleles as well as by its environment. An individual possesses two alleles for each trait; one allele is given by the female parent and the other by the male parent. They are passed on when an individual matures and produces gametes: egg and sperm. When gametes form, the paired alleles separate randomly so that each gamete receives a copy of one of the two alleles. The presence of an allele doesn’t promise that the trait will be expressed in the individual that possesses it. In heterozygous individuals the only allele that is expressed is the dominant. The recessive allele is present but its expression is hidden.

Mendel summarized his findings in two laws; the Law of segregation and the Law of Independent Assortment.


Histology is the study of the microscopic anatomy of tissues of plants and animals.


The animal tissues are classified into four categories:

(1) Epithelial tissues;

(2) Muscular or contractile tissues;

(3) Connective or supporting tissues; and

(4) Nervous tissues.

Epithelial Tissues

Epithelial tissues are the simplest of all animal tissues that form lining of various internal organs and also cover the surface of the body. The cells in an epithelial tissue are arranged in layers and there is no intercellular space. All these cells lie on a non-cellular basement membrane or basal lamina.

There is no blood or lymph supply to the epithelial tissues, however, nerve supply is present.

According to the number of layers and structure of cells, epithelial tissues are of the following types:

Simple Epithelium

Cells of this epithelium are arranged side by side to form a single layer only, lying on the basement membrane. It is of the following types:

(1) Squamous epithelium: Cells are extremely thin and flattened with clear cytoplasm. A single round or oval-shaped nucleus is present in the center of the cells. It is found in the lung alveoli, Bowman’s capsule, kidney tubules etc.

(2) Cuboidal epithelium: Cells of this epithelium are as long as broad in shape and appear cube-like. It is found in some parts of kidney tubules, ducts of salivary glands, thyroid gland, covering of ovary etc.

(3) Columnar epithelium: Cells of this epithelium are much longer than broad and hence look like a column. Their nuclei are situated in the center when these cells are not secretory and at the base when they are doing the function of secretion. It is found in the linings of alimentary canal, uterus and uterine tubes (fallopian tube). Its main function is secretion and absorption.

(4) Pseudostratified epithelium: Cells of this epithelium are tall column like arranged in a single layer but appears as if multi-layered due to different positions of their nuclei. It is found in male urethra, larger excretory ducts of many glands etc.

Compound Epithelium

(1) Transitional epithelium: It is seen in the regions which are subjected to different pressures as in the pelvis of kidney, urinary passage, urinary bladder etc.

(2) Straified epithelium: Cells of this epithelium are arranged in many layers one above the other. It is of the following types:

(i) Squamous epithelium: It is seen on the moist surface of buccal cavity, pharynx and the oesophagus. The top layer of cells may be keratinised (skin) or may be non-keratinised (vagina, oesophagus).

(ii) Cuboidal epithelium: The outermost layer of cells are cube like in appearance. It is found in the mammary glands, the ducts of sweat and larger salivary and pancreatic ducts.

According to the functions, epithelial tissues are of the following types:

(1) Glandular epithelium: This epithelium (usually cuboidal or columnar in shape) possesses delicate, hair-like   projections called cilia on their outer free surface. It is found in kidney tubules, trachea, oviduct etc. This epithelium   helps in the movement of substances.

(2) Glandular epithelium: The cells of this epithelium are columnar in shape. Some of these cells become modified to secrete musous. These unicellular gland cells are called goblet cells. It is seen in the intestine and other parts of alimentary conal.

(3) Sensory epithelium: The cells of this epithelium have nerve endings so that they can perceive various sensations. It is found in the nasal passage, taste buds, epidermis of earthworms, retina of eyes etc.

(4) Absorptive epithelium: The columnar cells of this epithelium have got villi and microvilli so that surface area of the cells is increased that helps in better absorption. It is found in the linings of alimentary canal.

Connective Tissue

A connective tissue serves to bind other tissues and organs and also support the body. It is mainly characterised by the presence of intercellular substances forming the matrix.

Connective tissue is of the following types:

(1) Areolar Connective Tissue: This tissue lies just below the epidermis of the skin, on many hallow visceral organs and on the walls of arteries and veins. Imbedded in the matrix are present mainly three types of cells:

(i) Fibroblasts: They are large, flat, spindle-shaped, branching cells with long protoplasmic processes and an oval nucleus in the center.

(ii) Macrophages: They are large and wandering cells with a central nucleus. They are phagocytic in nature i.e. ingesting bacteria, cell debris and foreign bodies. During and foreign bodies. During inflammation they may show amoeboid movements;

(iii) Mast Cells: They are usually find near the blood vessels. They produce histamines (constricts or dilates blood vessels) and heparin (an anticoagulant). These cells are usually stimulated by different chemicals called allergens.

Fibers in a general connective tissue are formed by the activity of fibroblast cells and are of three types:

(1) White or Collagenous fibres are thick, wavy, unbranched and non elastic.

(2) Yellow or elastic fibers are thin, straight, branched and highly elastic.

(3) Reticular fibers are thin, branching and usually form a network; they occur mainly in lymphatic organs.

(4) Adipose Connective Tissue: It is a specialised form of areolar tissue in which there are fat cells or adipocytes besides other cells. Collagen fibers and elastin fibers are also present. They function to store fat and are found underneath the dermis of skin, around kidneys and in mesenteries and bone marrow. It serves as a heat insulating layer underneath the skin. It also acts as a shock absorbing cushion around kidneys and eyeballs.

(5) White Fibrous Tissue: It provides a great tensile strength to the tissues. It is seen in the joints of skull bones that makes them immovable.

(6) Tendon: It is very thick, dense and strong connective tissue mainly composed of white collagenous fibers. Tendon help to join a muscle to a bone.

(7) Ligament: It is also a dense fibrous connective tissue but yellow elastic fibers are also present in between the white collagenous fibers. Ligaments help to join one bone to another bone at the joints and also hold them in position.

(8) Cartilage: A cartilage is a flexible and tough connective tissue. They have cells called chondrocytes and fibers. The cartilage is covered y a tough sheet of connective tissue called perichondrium. Deepending upon the structure, cartilage of the following three types:

(9) Hyaline cartilage: It is homogenous, translucent, crystal-like cartilage and is quite flexible. Hyaline cartilage is present in the articular surfaces of bones, nasal septum, trachea bronchus, front end of ribs etc.

(10) Fibrous cartilage: The matrix of this cartilage is mainly constituted by the white collagenous fibers and cells. It is present in the regions of intervertebral discs, pubic symphysis etc.

(11) Elastic cartilage: The matrix of this cartilage has more of yellow elastic fibers, which is present in all directions. It is present in the regions of pinna, external auditory meatus, epiglottis etc.

(12) Bone: Bone or osseous tissue is composed of an organic matrix with heavy deposition of inorganic salts. The matrix is made up of a protein called ossein and the inorganic salts are of calcium, phosphorus, magnesium, sodium, potassium etc., mainly it is calcium phosphate. About 65% of the dry weight of a bone constitute these salts. On the outside, bone is surrounded by periosteum through which blood vessels and nerve fibers enter in it; and an internal lining in the endosteum. In long bones inside the endosteum, bone marrow is present

It is of two types:

(i) Yellow marrow having mainly adipose tissues and blood vessels;

(ii) Red marrow is found at the extremities and manufactures red blood cells. It is found only in mammals.

Two types of bones are distinguished:

(i) Spongy or cancellous bones. It is found at the ends of long bones, in sides of round and irregular bones.

(ii) Dense or compact bone. It is comparatively hard and compact and found in the shaft of long bones, and outer layers of round and irregular bones.

(iii) Blood: Blood is a bright red coloured fluid connective tissue that circulates in the entire body. It consists of a straw coloured fluid called plasma in which various cells or corpuscles are seen floating or moving. Its volume is about 6-7 litres in an adult human body. It is a slightly alkaline fluid having the PH 7.2 – 7.4.


They form the living part of the blood and constitute about 40% of the total blood. They are of the following three types:

Erythrocytes or red blood corpuscles (RBC): They are large, biconcave disc-like structures without a nucleus. Under normal conditions, their number is approximately 5-6 millions/cu. Mm of blood. In a man the number is more than in a woman. However, their number increases during a muscular exercise. The life of RBC is about 120 days.

Erythrocytes contain a red coloured pigment called haemoglobin. With the help of haemoglobin, blood is able to transport oxygen from lungs to the tissues thus it helps in the process of respiration. Human blood has about 13-14% (females) and 14-15% (males) haemoglobin in its cells.

RBCs are manufactured in tissues called haemopoietic tissues and the process of their formation is called as hemopoiesis. In the developing foetus, the hemopoietic tissues are liver and spleen. But after the birth of the child, they are mainly produced in the red bone marrow of the long bones. The excess production of erythrocytes is stored in the spleen, which thus serves as a “blood bank” of the body. The old and worn ut erythrocytes are destroyed by the liver and spleen. The reticuloendothelial cells of liver, spleen and bone marrow remove the destroyed RBC and break down the haemoglobin into another iron containing pigment called hemosiderin and the yellow bile pigment bilirubin and green biliverdin. The bone marrow can use most of the iron again in the manufacture of new haemoglobin. During haemopoiesis, iron and proteins are needed for the manufacture of erythrocytes; while vitamin B12 and folic acid help in their maturation process. Therefore, deficiency of these substances in the blood causes anaemia. Deficiency of vitamin B12 particularly causes pernicious or megaloblastic anaemia.

Leucocytes or white blood corpuscles (WBC): They are large nucleated colourless cells and are much less numerous than erythrocytes (1:6000). They have a comparatively shorter life span, and no haemoglobin. Their number is about 7-8,000/cu. mm of blood. However,this number may rise in cases of acute infections like pneumonia and appendicitis (inflammation of vermiform appendix). In blood cancer or leukemia, number of WBC increases. In folic acid deficiency, the total count of W.B.C. decreases (leukopenia). WBC are of the following two types:

(a) Granulocytes: They have a granular cytoplasm and lobed nucleus. They are about 70% of the total leucocytes. Depending upon the stainability property of the cytoplasm, they are of three types; Basophils – the granules of cytoplasm are stained with basic dyes like methylene blue, the nucleus is somewhat spherical with indented outline; Acidophils or Eosinophils – the granules of cytoplasm are stained with acid dyes like eosin, the nucleus is usually two lobed joined by a narrow bridge; Neutrophils – have fine granules in their cytoplasm and are stained with neutral dyes or with a mixture of acid or basic dyes, the nucleus is multilobed.

(b) Agranulocytes: They have a clear (without granules) cytoplasm and unlobed nucleus and are about 30% of the total eucocytes. They are of two types: Lymphocytes – have a spherical and big nucleus occupying most of the cytoplasm; Monocytes – are large and have a kidney shaped nucleus. Both lymphocytes and monocytes are phagocytic in nature.

Blood platelets: They are small fragments of protoplasm with some granules. They are somewhat rounded colourless, biconvex and non-nucleated. They disintegrate at once when the blood is shed and thus help in the coagulation of blood. Their number is about 250,000-300,000/cu. mm of blood.

Muscular tissue

Muscle tissue is composed of differentiated cells containing contractile protein. The muscular system in man is very well developed. All the three types of muscles i.e. voluntary, involuntary and cardiac muscles are present in the body.

Voluntary muscles: These muscles are attached to the bones either directly or by tendons. Muscles are made of fibres. The plasma membrane covering each fibre is called sacrolemma. The cytoplasm inside is called sacroplasm. These sacroplasm contain many long, thin cylindrical structures called myofibrils. Thin myofibril has two types of filaments. Thick filaments are made up of the protein myosin. Thin filaments are made up of actin, tropomyosin and troponin.

Cardiac muscles: Cardiac muscles are restricted to wall of the heart. The sacroplasm poses abundant myofibrils, numerous mitochondria and glycogen granules. A unique and distinguishing feature of cardiac muscles is the presence of specialised junctional complex at the ends of the adjacent muscle cells called intercalated discs.

Involuntary muscles: Smooth muscles/involuntary muscles are a collection of fusiform cells that do not show any striation. They are widest at the midpoint and tapers towards the end. Each fibre contains a single, elongated nucleus. The mitochondria in the sacroplasm is fewer in number. These are present in stomach, intestine, blood vessels etc.

Rigor mortis

It is a condition in which the body muscles become still and rigid due to the non-availability of ATP molecules, enzymes and O2. Under such a situation, if the muscle is stimulated it will not show any response. It means death of muscle.

Constituents of Blood

Composition of blood plasma: The major portion of plasma is water (90% approx.) in which various organic and inorganic substances (10%) are dissolved giving it a straw-coloured appearance. The various inorganic components are in true molecular solution chlorides, bicarbonates, sulphates and phosphates of sodium, potassium, calcium, iron and magnesium. The organic components are proteins (fibrinogen, albumin and globulin), glucose, amino acids, fats, urea, hormones, dissolved gases like oxygen and carbon dioxide, antibodies and enzymes.

Blood glucose: Glucose is a major constituent and nutritive substance of blood plasma and also of erythrocytes. It is added to the blood by the absorption from the intestinal villi.Liver stores glycogen which is also broken down to form the glucose in the blood. Normally, a person has about 80-100 mg of glucose per 100 ml of blood 12 hours after a meal. But this amoung rises more (not exceeding beyond 180 mg) soon after a carbohydrate rich diet. However, the persistent high levels of glucose beyond this specified threshold value in the blood causes diabetes mellitus. It the amount of glucose in the blood rises beyond 180 mg per 100 ml consistently, then glucose starts appearing in the urine.

Blood cholesterol: About 50-180 mg of cholesterol is present in 100 ml of blood plasma. It is mainly used for the synthesis of new cell membranes by the body tissues, vitamin D, steroid hormones and bile salts. Liver synthesizes cholesterol and secretes it into the blood.

Blood Proteins: There are mainly three plasma proteins viz., albumin, globulin and fibrinogen. Their important functions are:

(i) They serve as a source of proteins for the tissue cells.

(ii) These may also be utilized for the formation of other cellular proteins.

(iii) Albumin and globulin can retain water in the blood plasma by their osmotic effects. That is why a person taking less proteins in the diet suffers from oedema (accumulation of water in the tissues).

(iv) These proteins are also known to transport many substances such as thyroxine and ferric ions.

(v) Globulin proteins may occur as immunoglobulines and in this form they behave as antibodies. The antibodies inactivate the invading microorganisms (antigens) and their toxins.

(vi) Some globulins can convert soluble fibrinogen into insoluble fibrin and thus help in blood coagulation.

(vii) Plasma proteins act as acid base buffers and thus help to maintain the blood PH by neutralizing strong acids and bases.

(viii) They help to distribute heat all over the body and also conducting heat to skin for dissipation.


In plants, there are basically two types of tissues based on the ability of the mature cells of the tissue to divide and produce new cells:

(a) Permanent Tissue; and

(b) Meristematic Tissue.

Permanent Simple Tissues


The parenchyma consists of living cells. It is found in the soft parts of the plant such as cortex of roots, ground tissues in stems and mesophyII of leaves.

Function: They store food and provide temporary support to the plant. It chloroplast is present, the tissue is called chlorenchyma and performs photosynthesis. These occur in the palisade of leaves.


The collenchyma tissue also consists of living cells. It is found in few layers below the epidermis of dicotyledon stems. It is generally absent in monocot stems, roots and leaves.


It gives mechanical support to the plant. If chloroplast is present (young dicot stems), then it manufactures food. Hence its function is mechanical and vital.


It consists of very long, narrow cells, tapering at the ends to resemble fibres. The cell walls are greatly thickened with lignin. The sclerenchyma occurs in abundance either in patches or definite layers. They are found in stems, veins of leaves, hard converings of seeds and nuts.


It gives strength, rigidity, flexibility and elasticity to the plant body and thus enables it to with-stand various strains.

Permanent Complex Tissues

The complex tissue consists of more than one kind of cells. The two main types of complex tissues discussed here are the xylem and phloem.


The xylem tissue is composed of four elements – tracheids, vessels, xylem fibres and xylem parenchyma.

The xylem tissue is found in all parts, such as the root, stem and leaf of the higher plants. They occur together with the phloem and form the vascular bundle.


Their main function is to conduct water and minerals upwards from the roots to the stem and leaves. Older xylem tissue form the wood and do not take part in conduction. Their walls being lignified, they also give mechanical strength to the plant.


The phloem is another conducing tissue consisting mainly of, sieve tubes, companion cells and phloem parenchyma. It is found in all parts of the plant like roots, stems and leaves.


It conducts prepared food from the leaves to the storage organs and growing parts of the plant.

Meristematic Tissue

These are composed of cells that posses the power of dividing. According to their position in the plant, meristems are apical, lateral and intercalary.

(a)   Apical: These are situated at the growing tip of stems and roots.

(b)   Lateral: These are found beneath the bark and in the vascular bundles of dicot roots and stem (known as cambium).

(c)   Intercalary: These are located at the base of the internode.


Apical meristem: Brings about the elongation of the root and stem.

Lateral meristem: Causes the organ to increase in diameter and girth.

Intercalary meristem: These produce an increase in length of the organ.

Animal Physiology & Anatomy


In most animals the body has a rigid framework called skeleton. It provides physical support and protection to the body. Basically, there are two types of skeleton:

1. Exoskeleton that occurs outside the body

2. Endoskeleton that occurs inside the body

Human skeleton consists of 206 bones. It can be divided into an axial skeleton and appendicular skeleton.


Skeletal system consists of many separate bones, most of which are held together at joints. Structurally, joints are classified as fibrous, cartilaginous and synovial.

(1) Fibrous joints: Bones are held by Fibrous connective tissue with no synovial cavity e.g. those found in skull and roots of teeth in alveoli of maxilla (upper jaw) and mandible (lower jaw).

(2) Cartilaginous joints: Bones are joined together by cartilages with no synovial cavity e.g. between vertebrates and pelvic girdle bone.

(3) Synovial joints: They contain synovial cavity and are movable joints. There is a fluid filled in the cavity called synovial fluid.

These movable joints are:

(a) Ball and socket joint e.g. shoulder girdle and hip girdle joint.

(b) Hinge joint e.g. elbow joint, knee joint, joint between fingers and toes.

(c) Pivot joint – movement of skull over the first neck vertebra.

(d) Gliding joint – e.g. wrist bones gliding over forearm bones.

(e) Saddle joint – it is poorly developed ball and socket joint e.g. metacarpals of thumb over its carpal.

Know your bones

(i) The only movable bone in the skull of man is mandible or jaw bone.

(ii) The vertebral column has 33 vertebrae.

(iii) Secrum has 5 vertebrae fused.

(iv) Coccyx has 4 vertebrae fused.

(v) Stapes in the ear is the smallest bone.

(vi) 1st seven pair of ribs are known as true ribs.

(vii) Pair 8th, 9th and 10th attach indirectly to sternum and are thus called false ribs.

(viii) 11th and 12th rib do not attach to sternum and are called floating ribs.

(ix) Femur is the longest bone.

(x) 1st vertebra is called atlas, it supports the head.

(xi) 2nd vertebra is called axis.

(xii) Hyoid is a U shaped bone that supports the tongue.

(xiii) Cavity in pectoral girdle is called Glenoid cavity.

(xiv) Cavity in pelvic girdle is called acetabulum.

(xv) Tooth enamel is the hardest substance in our body.


1. Arthritis: Inflammation of joints.

2. Slipped disc: The vertebrae are displaced from normal position in vertebral column.

3. Osteoporosis: Generally due to aging. Loss of calcium from bones decreases strength of the bone tissue.

4. Rickets: Vitamin D deficiency in children leads to the inability of the body to absorb calcium and phosphorus, as a result the bones become sot and bend under body weight.

5. Osteomalacia: Demineralisation caused by Vitamin D deficiency in adults.

Axial skeleton (80 bones)


Cranium – 8

Face – 14

Ear ossicles – 6

Hyoid bone – 1

Vertibral column vertebrae – 26 (cervical 7, thoracic, 12, lumbar 5, sacrum 1, coccyx 1)


Sternumm – 1

Ribs – 24

Appendicular skeleton (126 bones)

Upper regions

Pectoral girdle

Clavicle – 2

Scapula – 2


Humerus (upper arm) – 2

Radius – 2

Ulna – 2

Carpals (wrist) – 16

Metacarpals (palm) – 10

Phalanges (jingers) – 28

Lower extremities

Pelvic (hip) Girdles – 2

Femur (thigh) – 2

Tibia  - 2

Fibula – 2

Patela (knee cap) – 2

Tarsals – 14

Metatarsals – 10

Phalanges – 28


In mammals, the nervous system has three parts:

Central Nervous System

In consists of brain and spinal cord. The area inside brain and spinal cord where cell bodies of neurons are present appears grey in colour and hence called grey matter. While the other part which contains nerve fibres are called white matter. Whole central nervous system is surrounded and protected by a membrane called meninges. Inflammation of the meninges is called meninges is called meningitis.

Structure of brain: Brain is lodged inside the cavity of skull called cranium. It weighs about 1,3500 grams. The cerebrum is highly developed part of the brain and makes about 2/3rd of total brain. It is associated with memory, intelligence, thinking, reasoning etc and sensory perception of all the sense organs. The base of the brain constitute the hypothalamus. It contains the nerves centre for temperature regulation, hunger, thirst and emotions. The mid-brain joins the cerebellum. It has large numbers of nerve cells scattered within the white matter. The hind brain consists of cerebellum which acts as a centre for the coordination of activities of voluntary muscles. It helps in balance and equilibrium of body. The brain stem consists of pons varoli in front of cerebellum and medulla oblongata behind it. Pons varoli runs cross wise and carries impulses from one portion of cerebellum to another. The medulla oblongata lies in between pons varoli and spinal cord and control various reflexes like breathing, swallowing, salivation, schewing, coughing, sneezing, respiration and circulation.

Spinal cord: It is an extension of the medulla oblongata portion of the brain and passes out of the skull through Foramen Magnum. It passes through neural canal of the vertebral column.

It is instrumental in bringing about an involuntary response to stimulus which is not under the control of higher nervous centre i.e. the brain.

  • The spinal cord is a series of 31 sections called segments. Each segment giving rise to pair of spinal nerve.

  • The posterior or dorsal root contains sensory fibres only and conduct nerve impulses from periphery to spinal cord. It also has a swelling called dorsal root ganglion, which contain sensory neurons.
  • The ventral root contains motor neuron axon only and conduct impulses from the spinal cord to periphery.
  • The major function of spinal cord is to convey nerve impulses from the periphery to the brain and to conduct motor impulses from brain to periphery.

Peripheral Nervous System (PNS)

  • PNS is composed of spinal nerves and cranial nerves.
  • Neurons and nerve fibres conduct nerve impulses from the CNS to peripheral organ are called Efferent Neurons and Nerve Fibres.
  • Neurons and nerve fibres conduct nerve impulses from periphery to CNS are called Afferent Neurons & Nerve Fibre.
  • Neurons and nerve fibres which cause movement of the muscles are called Motor Neurons and Nerve Fibre. The motor nerve fibre is the axon of the motor neuron.
  • All motor neurons are efferent neurons.
  • The neurons and nerve fibres which conduct from periphery to CNS to evoke sensation like touch, pain, heat, cold etc are called Sensory Neuron and Nerve Fibre.
  • All sensory nerves are afferent in nature.
  • Some nerves carry simultaneously both sensory and motor nerve fibres; are called Mixed Nerves.
  • All nerves arising from the spinal cord are mixed nerves.

Autonomic Nervous System

This regulates the activity of visceral organs by regulating the activities of their involuntary muscles and glands associated with it. For example they control secretion of glands of the alimentary canals, the rate and force of heart beat, and secretion of adrenaline etc. Autonomic Nervous system has two parts sympathetic and parasymphathetic nervous system.

Functions of the Brain


Sensory areas interpret sensory impulses, the motor areas control muscular movements and the association areas are concerned with emotional and intellectual processes such as memory, reasoning, will judgement, etc.


1.  Co-ordinates muscular activity.

2.  Maintains body balance and posture.


It is the interpretation centre for sensory impulses such as pain, temperature, light touch and pressure.


1.  Controls normal body temperature, food intake and thirst.

2.  Regulates and controls the pituitary gland, being able also to produce its own hormones.

3.  Maintains the waking state and sleep patterns.

Medulla oblongata

1.  Regulates heart beat, breathing and blood vessel diameter

2.  Co-ordinates reflexes such as swallowing, vomiting, coughing, sneezing and hiccupping.

Pons Varoli

Together with the medulla, it controls breathing.

Mid brain:

It relays motor impulses from the cerebral cortex to the pons and spinal cord and relays sensory impulses from the spinal cord to the thalamus.

Sense Organs


Each eye is in the form of a spherical ball and is protected by upper and lower eyelids that can move frequently. Eyelashes are the margin of eyelids. The third eyelid or Nictitating membrance is reduced and vestigial in man and is found at one corner of the eye. On the margin of eyes are small Meibomain glands that secrete an oily substance to lubricate eyes and lachrymal gland to produce tears. Eyes are moved by a set of six muscles.

The eyeball is formed of the following:

Sclera: It is the outermost layer of the eyeball whose two third portion is opaque while on third is continued in front as transparent cornea. Sclerotic maintains the shape of the eyeball and is protective in function. Over the cornea another transparent membrane called conjunctiva is present which is an extension of the skin of eyelids.

Choroid: Next to sclerotic is vascularised and pigmented choroids. In front it thickens as a ring like ciliary body. It contains smooth muscle fibres forming the ciliary muscle. The choroids separates from the sclera and passes inwards as iris, which possesses a circular aperture in the centre called pupil. Suspensory ligaments are attached to the ciliary body that hold and support the spherical lens.

Retina: It is the sensory layer where the image is actually formed. It consists of two types of nerve cells rods and cones. A posterior part of retina contains only cones and has yellow colour as so called yellow spot.

In the middle of retina is a blind spot, which lacks both rods and cones. Usually the optic nerve arises from this spot.

  • External ear consists of Pinna and external auditory canal.
  • Pinna is funnel shaped cartilaginous flap. It collects and direct sound wave into ear canal.
  • The external canal ends at a delicate membranous diaphragm, called Eardrum or Tympanic Membrane.
  • The middle Ear is an air-filled chamber. It communicates with that of the pharynx through air filled tube called, Eustachian Tube.
  • Eustachian tube helps equalize air pressure on either side of ear drum and thus allow it to vibrate freely when sound wave impinge on it.
  • The vibrating eardrum transmits the vibration to ear ossicles. The ear ossicles consist the hammer (malleus), and anvil (incus), and the stirrup (stapes). The stirrup (Stapes) is the smallest bone in the body.
  • The ear ossicle transmits the vibration to the fluid Endolymph filling the inner ear.
  • The internal ear is made up of bony Labrynth and Membranous Labrynth. The bony labyrinth contains a fluid called Perilymph.
  • The cochlea is a bony canal making two and half spirals. Internally, canal is separated by membranes into three canals.
  • The sound heard with greatest clarity are those arising from sources which vibrate at frequencies between 1000 & 400 HZ. Te entire range of sound perception in human is between 20 HZ to 20,000 HZ.
  • The relative sound units are usually measured in decibels.


  • Receptors for smell occur in a modified pseudostratified epithelium covering a part of nasal mucosa, called Olfactory Epithelium. It is more extensive in animals like dog, with an acute olfactory sense.
  • The olfactory epithelium consists of three type of cells viz Olfactory receptor cells, Supporting cells and Basal cells.
  • The Olfactory receptor cells function as Chemoreceptors.
  • A substance must be capable of entering into a gaseous state so that it can enter into nostrils to be smalled. It also must be water soluble so that it can dissolve in the mucus to make contact with olfactory cells.

Eye: Functional Aspects

Adaptation: Sensitivity of eye to light depends on illumination of object.

Accommodation: Adjustment of eyes in order to assure clear vision of object at different distance is called accommodation.

Stereoscopic Vision: The ability to perceive depth is due to simultaneous focusing of object in both eyes. The overlapping of their images in brain gives a 3-dimensional effect.

The impression of an image remains on the brain for 1/10 of second. In motion picture, picture is shoot at the speed of 14 frames/sec and then projected through a high speed projector.

Sensitivity and Vision

  • Human eye is sensitive only to wavelength ranging from 380 to 760 nm.

  • Rods are sensitive even to dim light and enable us to see in dim light and at night. It contains purple coloured pigment called Rhodopsin, formed from vitamin A. Many nocturnal animals like owl, have only or mainly rods as photo   receptor. Rods, however, cannot help in seeing colour.
  • Cones are sensitive to bright light only. Animal like sparrow have only or mostly cones in their retina. Cones are also responsible for perception of colour. Cones contain violet-coloured pigment called Idopsin.
  • Human being, apes, monkey, birds, lizards, turtles, and some fishes posses colour vision.
  • Most domestic mammals, sharks do not possess colour vision.
  • Bee can see ultraviolet light.
  • Eyes capable of focusing the images of objects are possessed only by vertebrates and some higher invertebrates like prawns, crabs and insects.

Selected Defects of the Eye

A normal eye can sufficiently refract light rays from an object 6m (20 ft) away to focus a clear image on the retina. Many people lack this ability due to abnormalities related to improper refraction. Among these types of disorders are myopia, hypermetropia, astigmatism and presbyopia.

Myopia (short sight): Near vision is clear while distant vision is blurred. This occurs if the light rays entering the eye converage in front of the retina in the vitreous body. Since the light rays are brought to focus without reaching the retina, the light is dispersed on it instead of being concentrated. This could happen due to one of the following reason.

(1) The lens is too convex.

(2) The longitudinal axis of the eye is too long (eye ball too elongated from front to back)

Corrective lens: By the use of concave lens, which reduce the refractive power of the lens and thus bring the image on the retina.

Corrective lens: This optic abnormality can be corrected with a biconvex lens, which intensify ray refraction.

Corrective lens: Cylindrical lens or contact lenses can correct this defect.

Presbyopia: It is the inability to focus on nearby objects due to loss of elasticity of the lens with age. This condition generally occurs after the age of 40. As result, those already wearing glasses go on to bifocal while those who have not previously needed glasses may require glasses.


  • Taste buds are oval bodies found in some elevation in tongue called papillae.
  • Human being recognise four basic modalities or tastes sweets, sour, salty and bitter.
  • Sweet, sour, salty and bitter tastes are principally perceived at the tip, along lateral edges, on upper surface of front half, and on the back of the tongue; respectively.
  • Some taste buds are stimulated by a single specific modality of taste like sweet or sour, others are sensitive to two or more modalities.
  • Sour taste evoked by H+ ions is produced by ionisation of acids.
  • Sweet taste is evoked by organic substance viz sugar, dextrin, glycerol, chloroform, aspartame and saccharine.
  • Bitter taste is evoked by quinine, morphine, caffeine, nicotine, and urea. It is also produced by cation of many inorganic salts like Magnesium salts.
  • Salty taste results mainly from cations like Na+.
  • Loss of smell reduces the perception of taste also. This shows that much of what we think of as taste is actually smell.
  • Taste of chillies, black pepper, and hot sauces are not true sensation. It is mainly a sensation of burning pain produced by stimulation of pain receptors.
  • Many insects such as honey bee, flies, butterflies and moth, possess chemoreceptors for taste sensation at their feet.
  • Some mammals like rhesus monkeys, dogs, pigs, and cats posses taste sensation for water.


Hormones are chemical substances produced from ductless glands. Chemically, they may be polypeptides steroid and biogenic amines. Hormones are always poured into venous blood.

Endocrine glands: These are ductless glands. They secrete their products (hormones) into the extra cellular space around the cells. The secretions then pass into capillaries to be transported in the blood.

Example: Pituitary, thyroid, adrenal.

Exocrine glands: These have ducts. They secrete their products (oil, sweat, enzymes) into ducts, the ducts carry the secretion into body cavities, lumen of various organs or body surface.

Example: Sweat gland, sebaceous gland, digestive gland, mucous gland.

Hypothalamus: It is a part of the brain that consists of several masses of grey matter called hypothalamic nuclei. Neurons of the hypothalamic nuclei control the activity of pituitary gland.

Hypothalamus secretes several hormones called neurohormones that reach the anterior pituitary by hypophseal portal vessels, and control the secretions of the hormones from it.

Pituitary gland (Hypophysis): It is also known as ‘master gland’. It is about the size of a gram that hangs below the hypothalamus by a stalk called infundibulum.

Thyroid gland: It is found on the ventral side in the neck region of the body. At the base of larynx, it has two lateral lobes on either side of Trachea. It is the largest endocrine gland in the body. It has the greatest concentration of iodine.

Thyroxine secreted by thyroid stimulates metamorphosis in frogs.

Parathyroid glands: They are four small oval shaped bodies two on each side of thyroid. They are present in all vertebrates except fishes.

Thymus: It is a small gland situated behind the sternum. It is active during childhood and gradually disappears in the adult. It produces a hormone called thymosin or thymin that stimulates the proper differentiation of lymphocytes. Later on, in adults, this function is taken up by the lymph glands.

Pineal: It lies in the brain near pituitary gland and secretes a hormone called melatonin. It is an antigonadal and may delay the sexual development. Pineal also secretes secrotonin that acts as a vasoconstrictor increasing the blood pressure.

Adrenals: There are two adrenal glands, one on the top of each kidney. Adrenal gland has an outer portion called cortex and an inner portion called medulla. Adrenal medulla contributes to fright, fight or flight reactions thus preparing the body for emergency conditions. Adrenaline is also known as emergency hormone.

Pancreas: Pancreas is a mixed gland (heterocrine). Its endocrine part forms the Islets of Langerhans and produce the following protein harmones:

Insulin: It is a protein hormone produced by - cells of Islets of Langerhans. It regulates the amount of glucose in   the blood by converting excess of glucoe into glycogen (glycogenesis), which can be stored in the liver and muscles. Lack of insulin results in excess glucose in the blood (hyperglycemia) so much so that it starts appearing in urine (glycosuria). Insulin is also called anabolic hormone.

Glucogen: It is also hormone produced by -cells of Islets of Langerhans. It also regulates the amount of glucose in the blood by converting glycogen back to glucose (glycogenolysis), whenever required. Thus its effect is opposite to that of insulin.

Testis: There are a pair of testis outside the abdominal cavity in scrotal sacs in males. Leydig cells present in the testes form its endocrine part and produce male sex hormone called testosterone. Testosterone apart from doing other functions stimulates the growth of many body tissues like bones and muscles.

Placenta: It is a structure formed by the maternal and foetal tissues for the exchange of various substances between the mother’s body and the developing foetus.

The placenta, secretes oestrogens, progesterone and relaxin, all of which are related to pregnancy.

Tissue Harmones

Body tissues other than those usually classified as endocrine glands also contain endocrine tissues and thus secrete hormones. Some of the important endocrine tissues are:

(1) Those of the gastrointestinal tract (stomach, intestines), which influence the production and secretion of digestive juices.
(2) The tissues of the kidney, which produce hormones that stimulate the production of red blood cells.

Differences between hormones and enzymes


(1) They are produced from glands having ducts (exocrine gland).

(2) Chemically, they all are protein in nature.

(3) They remain unchanged at the end of reaction (catalyst).

(4) They are produced in an organ where they perform their function.

(5) They are not transported through blood e.g. Pepsin, trypsin.


(1) They are produced from glands without any duct (endocrine gland).

(2) Chemically, they can be protein, steroid, polypeptides etc.

(3) They are used up during a metabolic reaction.

(4) They are produced in an organ other than they perform their function i.e. they have a target organ.

(5) They are easily transported through blood e.g. insulin, estrogen.






Endocrine secretion




Oestrogen, Progesterone, relaxin (in pregnant females only)

Disease due to malfunctioning of Thyroid gland

Excessive secretion of thyroxine results in exophthalmic goiter or Grave’s disease. It is accompanied by bulging of the eyeball, a rise in heart beat and blood pressure, restlessness, tremors, nervousness.

Less secretion of thyroxine from thyroid (hypothyroidism) causes less tissue metabolism, less heat production, heart beats are slowed. This disease in adults in known as Myxoederma (Gulls disease). In children Cretinism is caused due to hypothyroidism, which has two important symptoms viz. Dwarfism and mental retardation.

For the synthesis of thyroxine, an important inorganic ion called iodine is needed in the body. Lack of iodine causes goiter, in which thyroid gland enlarges in an effort to produce more thyroxine.

Hashimoto’s disease: In this antibodies are produced in response to thyroid antigens. It is also known as death of Thyroxine.

Disorders due to Adrenal Cortex

1. Addison’s disease: It is usually caused due to tuberculosis of the gland involving both cortex and medulla. Thus there is less secretion of cortisol and aldosterone.

2. Cushing’s syndrome: It occurs due to adrenal tumor or adrenal hyper plasma when there is an excessive secretion of cortisol hormone.

3. Aldosteronism: It is caused due to the excessive secretion of aldosterone, this results in a decrease in body’s potassium level.

4. Adrenogenital syndrome: It is caused due to secretion of excessive sex hormone. Male develops few female characters (Gynecomastia) female develops few male characters (Virilism).

Summary of the sources, chemical nature and important

functions of various mammalian hormones





(1) Thyrotropin Releasing Hormone

(2) Corticotroin Releasing Hormone

(3) Gonadotropin releasing Hormone

(4) Somatostatin

(5) Growth Hormone (GH)

(6) Adreno-corticotrophic hormone (ACTH)

(7) Thyrotropin (TSH)

(8) Follicle stimulating hormone (FSH)

(9) Luteinising hormone (LH)

(10) Prolactin

(11) Melanocyte stimulating hormone (MSH)

(12) Oxytocin

(13) Antidiuretic hormone (ADH) or Vasopressin

(14) Melatonin

(15) Thyroxine

(16) Parathormone

(17) Calcitonin

(18) Cortisol (Glucocorticoids)

(19) Aldosterone (Mineralocorticoids)

(20) Adrenaline and Nor-adrenaline

(21) Insulin

(22) Glucogen

(23) Testosterone

(24) Estradiol

(25) Progesterone

(26) Relaxn

(27) Human chorionic “Gonadotropins” (HGC)





Anterior pituitary

Anterior pituitary

Anterior pituitary

Anterior pituitary

Anterior pituary

Anterior pituitary

Intermediate lobe of pituitary

Produced from hypothalamus and released from posterior pituitary

Produced from hypothalamus and released from posterior pituitary





Adrenal cortex

Adrenal cortex

Adrenal medulla

a-cells of islets of Langerhans

b-cells of islets of Langerhans

Testis (Leydig cells)

Ovary (Graffian follicle celsl)

Ovary (Corpus luteum)

















Iodinated amno acid





Biogenic amine








Stimulates anterior pituitary to secrete TSH

Stimulates anterior pituitary to secrete ACTH.

Stimulates anterior pituitary to secrete FSH and LH.

Inhibits the secretion of GH from anterior pituitary.

Stimulates the growth of the body.

Stimulates adrenal cortex to secrete mainly the glucocorticoids.

Stimulates the secretion of thyroxine from the thyroid.

Stimulates gametogenesis in males and females; along with LH stimulates estradiol secretion from the ovary.

Stimulates testosterone secretion from testes and progesterone secretion from overies; along with FSH stimulates estradiol secretion from ovaries.

Stimulates the secretion of milk from mammary glands.

Skin colour in amphibians.

Contracts uterine muscles at the time of child birth; expulsion of milk from mammary glands.

Reduces urinary loss of water; arteriolar constriction.

Antigonadal; makes skin pale (in amphibians).

Increase cellular metabolism and energy production: helps in growth and differentiation.

Increases blood calcium levels.

Lowers blood calcium levels.

Increases glucose formation from proteins: raises blood glucose levels (anti-insulin effects).

Increases sodium retention and potassium elimination.

Increases rate and force of heart beats, blood glucose, heat production, O2 consumption, relaxes smooth muscles etc.

Lowers blood glucose and increases glucose utilisation.

Increases blood glucose and lower liver glycogen.

Regulation of growth, development and functions of male secondary sex organs and characters.

Regulation of growth, development and functions of female sex organs and characters. Control of menstrual cycle and changes during pregnancy.


Softening of pelvic ligaments at the time of child birth.

Stimulatin of progesterone from ovary during pregnancy.


Animals derive energy from food, which they eat. The food in the body is digested to glucose and other simple compounds. It is this glucose that is oxidized by oxygen in the cells to yield energy (ATP) and CO2. This process of oxidation is termed as respiration and can be represented by:

Anaerobic respiration occurs in absence of oxygen and is seen in some loer organisms like bacteria and yeast, and many parasitic animals like tapeworm and liver fluke.

Even in human skeletal muscles during vigorous exercise respire anaerobicaly, thus glucose instead of oxidizing to  and  changes to lactic acid and we feel Fatigue.

In simple animals like amoeba, paramecium and plants there is no special organ of respiration.

In earthworms and leeches respiration occurs through the skin (cutaneous respiration). In them, haemoglobin is dissolved in plasma and not present in the corpuscles.

Aquatic animals like prawns, fishes and tadpoles respire in water with gills. In birds lungs take the form of a elastic air sac.

Respiratory organs in mammals

Mammals have lungs for the purpose of respiration (pulmonary respiration). The different organs involved in respiration are:

(1) Nasal cavity: It is a large cavity lying dorsal to the mouth and is lined by mucous secreting epithelium. Air while passing through the nasal cavity is filtered, and only clean air free from dust particles, bacteria and foreign substances enters the pharynx. The air also gets warmed and moistened in this chamber.

(2) Nasopharynx: It is a chamber situated behind the nasal cavities.

(3) Larynx: It is a small chamber situated in the region of neck. It is supported by four cartilages, thyroid (largest of the four), cricoids, arytenoids and epiglottis (situated behind the tongue that serves to cover the entrance to larynx so that food particles may not enter into it). Larynx is also known as voice-box, since it helps in the production of sound. In mid ventral portion larynx forms a protuberance called Adam’s apple.

(4) Trachea: It is a tube starting from larynx running through the neck and the thoracic cavity. It is supported by C-shaped cartilaginous rings, which prevent it from collapsing. It divides into two bronchi in the thoracic region.

(5) Bronchi and Bronchioles: The two bronchi enter into right and left lungs of either side. Inside the lungs they further branch into may smaller bronchioles. Each bronchioles divide into a number of alveolar ducts, which at the ends swell up into air sacs or alveoli.

(6) The exchange of O2 and CO2 takes place from the surface of alveoli.

The intercostals muscles and diaphragm take part in the process of respiration. Inspiration is an active process. During inspiration both inter costal muscles and diaphragm contracts.

Common diseases

(1) Asthama- It is the difficulty in breathing due to spasms of smooth muscles of bro nchi and bronchioles.

(2) Emphysoma: It is a condition in which the walls separating the alveoli break.

(3) Carbon monoxide poisoning: Co combines with haemoglobin more rapidly than O2 to form carboxyhaemoglobin.This is a stable compound and thus does not leave haemoglobin for transportation of O2. Such a person is kept in an O2 tent and given carbogen (95% O2 with 5% CO2) and causes headache, dizziness, nausea and even death.

Gas transportation in blood

  • Oxygen transport: Most of the oxygen is carried in chemical composition in the erythrocytes. Very less O2 or CO2 get dissolved in plasma.
  • Each of the  ions in haemoglobin molecules can bind one molecule of oxyen.
  • Oxyhaemoglobin does not dissociate before blood reaches tissue capillaries. The more active the tissue, the lower is its partial pressure of O2 (PO2) and higher it.
  • Carbon transport: Most of CO2 enters into RBC by diffusion, and react with water to form Carbonic Acid.
  • Some of the bicarbonate (HCO3) is carried in RBC while most of it comes out in plasma to be carried by it.
  • About 3% of CO2 entered into RBC, combined with globin part of deoxyhaemoglobin to form carbaminohemoglobin.


All higher animals have well developed circulatory systems so that transport of O2 & other materials in the body can be done effectively. In them the circulatory system consists of a central pumping organ called heart and various other blood vessels (arteries, veins and capillaries).

The inner most layer of artery has involuntary muscles. Capillaries are extremely fine, thin blood vessels, the walls of which are made of only a single layer of endothelial cell. Around the organs and tissues there is a fine network of capillaries.

The walls of these capillaries are so thin that the exchange of food materials, waste materials and gases takes place between blood and tissues.

The Heart

  • The heart is the pumping organ of blood vascular system.
  • The chamber which receives blood returned from the other tissue is one or two Auricles and in some animals, a Sinus Venosus.
  • The heart chambers pumping blood to different tissue consist of one or two Ventricle.
  • Fish heart contains and pump only deoxygenated blood, it has sinus venosus, a single auricle and single ventricle.
  • Amphibian and Reptilian heart pump both deoxygenated and oxygenated blood. Their auricle is completely partitioned. But ventricle in amphibian is unpartitioned, while in reptiles, it is incompletely partitioned into two.
  • Sinus venosus is present in fishes, amphibian and reptiles. In mammals and birds it is totally fused with the right auricle.
  • In mammals heart contain two auricles and two ventricles.
  • It is located centrally between lungs and held in position by pericardium, which is a connective tissue membrane consisting of two layers. Between pericardial layers is a fluid filled cavity that prevents friction between the two surfaces.
  • The wall of heart is divided into three layers.

Course of Circulation though Mammalian Heart

  • The contraction and relaxation of cardiac chambers are respectively known as Systole and Diastole.
  • The phase during which both Auricles and Ventricles are in diastole and are relaxed simultaneously, is called Joint Diastole.
  • During this phase, blood continues to flow into auricle through great veins and also from auricle to respective ventricle, but no blood flows from ventricles to great arteries.
  • At the end of this phase, the next heart beat starts with the contraction of auricle (Atrial systole), and ventricle still in diastole (ventricular diastole).
  • Atrial systole, replaces by arterial diastole and ventricle diastole replaces by ventricle systole systole.
  • With the rise in pressure in ventricle AV (Atrioventricular Valve) valves are shut sharply to prevent back flow of blood, which produces a sound ‘Lubb’ in the heart, this is the first heart sound.
  • With the onset of ventricular diastole, pressure falls in ventricle below that in great arteries, and semilunar valve closes and produces a sound ‘dup’. This is the second heart sound.
  • Human heart beats at the rate of about 72 beats/min in the resting condition.
  • Tachycardia: A rapid heart or pulse rate of over 100/min.
  • Bradycardia: A slow heart rate of below 60 min.
  • The smaller the animal, the higher it’s metabolic rate and consequently greater is the need for pumping action of the heart.
  • The heart rate increases during exercise, fever and emotions like anger and fear.
  • The remnant of the sinus venosus in mammals is represented by Sinoatrial Node (SA node). The cardiac impulse normally originates from SA nodes. It is also called pacemaker of heart.


  • Systematic circulation is maintained by left side of the heart. The left ventricle ejects blood into aorta, which gives off arteries to tissues and organs other than lungs, blood is returned from these tissues and organs through two veins, superior and inferior venae cavae.
  • Pulmonary circulation is maintained in right side of heart.
  • In some cases, a vein returning blood from a system of capillaries divides again in second capillary system in tissues before the blood finally return to the heart. Such a vein is called Portal Vein e.g. hepatic portal vein returns blood from the intestine and breaks into a portal system of capillary into liver, this enables the liver cell to take up from the portal blood the nutrient brought by it from small intestine.

Blood pressure, Normal BP is 120 mm of Hg during systolic phase and 80 mm of Hg during diastolic phase.

It BP persists at 140/90, the person is suffering from hyper tension, which can be caused by emotional stress, fear, worry, anxiety, sorrow, joy etc. Physical and mental rest is the remedy for hyper tension.

Blood grouping. The surfaces of red blood cells contain genetically determined antigens called agglutinogens. The type of antigen present in an individual forms the basis for classifying people under different blood groups.

  • A: Individuals with only agglutinogen A.
  • B: Individuals with agglutinogen B.
  • AB: Both agglutinogens are present.
  • O: Neither agglutinogens are present.

The blood plasma of many people containgenetically determined antibodies called agglutinins.

  • Plasma of group A has antibody b
  • Plasma of group B has antibody a
  • Plasma of group AB has no antibodies
  • Plasma of group O has antibodies a and b

Difference between Arteries & Veins


(1) Blood flows away from the heart
(2) Blood flows with a jerk and with great pressure
(3) They always carry oxygenated blood except the pulmonary artery
(4) Walls of arteries are thicker
(5) Valves are absent
(6) They are deep seated
(7) Their walls are elastic and muscular
(8) Non collapsible


(1) Blood flows toward heart
(2) Blood flows smoothly and with less pressure
(3) They always carry deoxygenated blood except the pulmonary vein 
(4) Walls of veins are thinner
(5) Semilunar valves are present
(6) They are superficial
(7) Their walls are non elastic and fibrous
(8) Collapsible


The skin is the largest of all body organs. It is an uninterrupted layer of tissue forming the water proof supple covering that gives body a proper shape. The skin is also one of the five sense organs. It enables us to perceive our environment by touch.

The integumentary system: The skin, together with Skin derivatives like hair, nails, glands and several specialised receptors, constitute the integumentary system.

Parts of the integumentary system: Skin visible to the naked eye is nothing but dead and dying cells in several layers. The chief functional layers of the skin are:

Epidermis: The epidermis is the outermost layer of the skin composed of thin stratified squamous epithelium. The epidermis lacks blood vessels.

Main regions of the epidermis

(a) Stratum corneum or the cornified layer: The outermost layer of the epidermis consists of 25 to 30 rows of flat dead cells completely filled with keratin. Keratin is also found in nails, hair, horns and hoofs.

(b) Stratum granulosum or the granular layer: This layer consists of three to five rows of flattened cells which lie below the cornified layer.

(1) These are concerned with the formation of keratin.

(2) The nuclei of these cells are in various stages of disintegration and as such incapable of carrying our vital metabolic functions.
(3) This layer gives way to the outermost cornified layer.

(c) Stratum germinativum or the malphigian layer: The deepest layer of the epidermis consists of a single layer of columnar cells.

(1) These are living cells capable of continued cell division.

(2) Cells from this layer migrate to the dermis and give rise to the sweat gland, sebaceous gland and hair follicles. The skin pigment melanin produced in this layer absorbs the harmful ultra-violet rays emanating from the sun.

Dermis: The dermis is the second principal part of the skin. It is composed of the following:

(a) Papillary region: The upper region of the dermis consists of loose connective tissue and has its surface greatly increased by small finger like projections called dermal papillae.

Functions of the papillary region

(1) The connective tissue contains collagen and elastic fibres that make the dermis tough and flexible.
(2) The blood capillaries provide nourishment to the skin.

(3) Secondary corpuscles (Meissner’s corpuscles) and nerve endings are sensitive to touch.

(4) Epidermal ridges increase friction for better grasping ability.

(b) Reticular region: The remaining part of the dermis is called the reticular region. It is attached to the underlying organs such as bone and muscle by the subcutaneous layer.

The main reticular region is packed with interlacing bundles of fibres. Spaces between the fibres are occupied by adipose tissue, nerves, hair follicle, ducts of oil gland, and sweat gland.


Hair is a fine thread-like structure forming the exoskeleton of mammals. It has the following functions:

(a) Provide Warmth: In most animals (with thick furs) it serves to provide warmth by trapping an insulating layer of air.

(b) Protection: In some animals it provides protection as in the case of porcupines and hedgehogs. The quills of porcupine or hedgehog are special types of hair.

(c) Sensory: Hair growing on the cheeks of certain mammals like cats, dogs, rodents, etc are sensory in function. Commonly known as whiskers, many nerves lie around these tactile hair and respond to touch and help the animal to feel their way around.

Sebaceous gland: The sebaceous glands lie in the dermis and open into the neck of hair follicles. These glands secrete an oily substance called sebum which is a mixture of fats, cholesterol, proteins and inorganic salts.

Some common problems associated with the sebaceous glands are:

(1) Acne: It is an inflammation of the sebaceous glands and usually occurs at puberty under the influence of certain hormones.

(2) Blackhead: Sometimes the sebaceous glands of the face become enlarged due to accumulated sebaceous glands of the face become enlarged due to accumulated sebum. Melanin and oxidized oil give it a black colour.

(3) Pimples: The sebum being nutritive to certain bacteria, often gets infected and results in the formation of boils and pimples.

Sweat gland: The sweat gland is a simple, coiled, tubular gland distributed throughout the dermis except in certain regions such as the margin of the lips, nail bed, genitals and eardrum. They are most numerous in the skin of the soles and of the palm.

(a) The secretary part of the gland, which occurs as a coiled tube, is located in the subcutaneous region of the dermis.

(b) The excretory part of the gland, known as the sweat duct projects upwards through the dermis and epidermis and terminates on the skin surface as an opening called the sweat pore.

Composition of sweat

Perspiration or sweat is a watery secretion produced by the sweat gland. It consists mainly of water and salt (NACL) minute quantities of metabolic wastes such as urea, uric acid, ammonia etc. It thus helps to eliminate wastes. Sweat is odourless until it has been broken down by bacteria on the skin surface. After decomposition it acquires a generally unpleasant odour. The evaporation of water from the sweat removes large quantities of heat from the body surface and cools the body.

Lymphatic system

The lymphatic system consists of a straw-coloured fluid called lymph; vessels that transport lymph called lymphatic vessels and a number of structures and organs that contain lymphatic tissue (lymphoid)

Lymph nodes

Scattered throughout the body usually in groups, these oval or bean-sharped structure act as filtering stations. The lymph passing through the nodes is filtered of foreign substances, trapped by the reticular fibres within the node.

The nodes also contain lymphocytes, which destroy microbes either by phagocythosis or by releasing antibodies. A large number of lymph nodes are located in the armpit and the groin. These nodes localise infection, for example, an infection in hand may cause painful swelling of the lymph glands in the armpit. Sometimes, the trapped bacteria infect lymph nodes, causing acute inflammation and abscess formation. This is commonly observed in the case of tonsils, which are multiple aggregations of large lymphatic nodules embedded in a mucous membrane.

The spleen is the largest mass of lymphatic tissue in the body, measuring about 12 cm in length. Located in the region between the fundus of the stomach and diaphragm, the spleen produces artibodies, phagocytizses bacteria and worn out or damaged red blood cells and releases it in emergency.

The thymus, an endocrine gland is also an important lymphatic organ.

The lymphatic system is also subject to diseases of its own. In elephantiasis, for example, a thread like parasite (Wuchereria brancrofti) renders the lymphatic tissue incapable of draining off the fluids that collect in the tissue spaces. This results in swollen water logged lower limbs and coarsened skin.


Reproduction is a process by which the continuity of a species is maintained. The mode of reproduction may be sexual or asexual.

Asexual reproduction: This type of reproduction involves a single individual and male and female gametes are absent. It generally involves a simple process of cell division as seen in amoeba and bacteria which reproduce by binary fission or in yeast and hydra which reproduce by budding.

Even flowering plants, which bear male and female gametes, can be propagated asexually from their vegetative parts like roots, stems and leaves.

Sexual reproduction: This mode of reproduction involves the union of male and female gametes. The fusion of gametes result in the formation of a zygote from which the new individual develops. This process is termed as fertilization.

In animals, the male and female gametes are generally produced in separate individuals. The male gamete is called sperm and is produced in the testes. The female gamete is called the ovum or egg and is produced in the ovaries.

In certain animals like the snail and tapeworm, both sex organs (testes and ovary) are present in a single individual. These animals are called hermaphrodites.

In plants, the sexes may or may not be separate. Accordingly, flower is either unisexual (bearing either male or female gamete) or bisexual (bearing both gametes).

Gametes and Somatic Cells

Gametes as reproductive cells differ from other body cells in that they contain haploid (one half) chromosome number symbolized as ‘n’.

Body cells (somatic cell) contain diploid chromosome number symbolized as ‘2n’.

Reproduction in Humans

Human beings reproduce sexually. The organs of the reproductive system are divided according to their function as primary and accessory parts.

The primary reproductive parts (testes and ovary) are those that help in the process of union of the two gametes.

The testes (or testicles)

The testes are a pair of oval glands ling outsides the abdominal cavity and enclosed in a loose cutaneous pouch called scrotum.

The testes develop on the posterior abdominal wall and descend into the scrotum a little prior to birth. The location of the scrotum a little prior to birth. The location of the scrotum and the contraction of its muscle fibres regulate the temperature of the testes.

The production and survival of sperms require a temperature that is lower than the normal core body temperature. Since the scrotum is outside the body cavity it provides an environment that is about 2C below normal body temperature.

Internally, each testis is divided into nearly 200-300 compartments called lobules.

Seminiferous tubule: Each lobule contains one to three tightly coiled tubules called the seminiferous tubule. It produces sperms by a process called spermatogenesis.

Interstitial tissue: Between the seminiferous tubules are clusters of cells forming the interstitial tissue. It secretes the male hormone testosterone.


(a) Ducts of the testes: The sperms move out of the convoluted seminiferous tubules into straight tubes and leave the testes through a network of ducts.

(b) Epididymis: The sperms leaving the testes enter a single tube called the epididymis. The epididymis is a comma-shaped highly coiled organ, which measures almost six metres, The head of the duct forms a tubular knot fitting like a cap on the upper pole of the testes. The body of the epididymis continues along the sides of the testes. The tail of the epididymis turns upwards and continues as the sperm duct or the vas deferens.

(c) Vas Deferens: Measuring about 45 cm, the vas deferens is a muscular sperm duct that ascends along the posterior border of the testes, penetrates the inguinal canal, enters the pelvic cavity where it loops over the urinary bladder and then descends to join the urethra at the back of the urinary bladder.

(d) Ejaculatory duct: Posterior to the urinary bladder, the vas deferens and the duct from the seminal vesicle unite to form the ejaculatory duct, which is about 2 cm in length. It ejects sperms into urethra.

Accessory glands

(a) Seminal vesicles: The seminal vesicles are a pair of convoluted pouch-like structures, lying posterior to and at the base of the urinary bladder in front of the rectum. They secrete an alkaline and sugary fluid and pass it into the ejaculatory duct. This fluid constitutes about 60% of the volume of semen.

(b) Prostate gland: Circling the urethra at the base of the urinary bladder, is a single doughnut-shaped gland celled the prostate gland. Its secretion constitutes 13-33% of the volume of semen.

(c) Cowper’s gland: A pair of ovoid glands (approximately the size of peas) called the cowper’s gland are located beneath the prostate on either side of the urethra. Their ducts open into the urethra.

Semen or Seminal Fluid: Semen is a mixture of sperms and the secretions of the accessory glands. It is slightly alkaline (PH = 7.2 to 7.6)

Female reproductive system

The following chart outlines the parts and functions of the female reproductive system.

1. Ovaries: The ovaries are a pair of glands resembling unshelled almonds in size and shape. They are positioned in the upper pelvic cavity, one on each side of the uterus. They are held in position by a series of ligaments and attached to the broad ligament of the uterus. It is richly supplied with blood vessels and nerves.

2. Uterine (fallopian) tubes: Extending laterally on each side of the uterus is a tube measuring about 10 cm in length. The open distal end of the tube is funnel-shaped and is called infundibulum. It is fringed by finger like projections called fimbriae. One fimbria is attached to the lateral end of the ovary. Internally, the muscular walls of the oviduct are lined with ciliated epithelium.

3. Uterus: The uterus is a pear-shaped, hallow, muscular organ situated between the urinary bladder and the rectum.

Before the first pregnancy, an adult uterus measures about 75 cm in length, 5 cm in width and 2.5 cm in thickness. The subdivisions of the uterus are.

Funds: It is the dome-shaped portion above the uterine tubes.

Body: It is the tapering central portion above the uterine tubes.

Cervix: It is the lower narrow portion opening into the vagina.

The Interior of the body of the uterus is called the uterine cavity. The innermost layer of the uterus called the endometrium is lined with secretary and ciliated cells.

4. Vagina: It is a tubular fibro-muscular organ lined with mucus membrane and lying between the urinary bladder and the rectum. It measures about 10 cm, extending from the cervix to the vestibule. It is streachable and functions as birth canal. At the lower end of the vaginal opening there may be a thin folder membrance called the hymen, which    forms around the opening, partially closing it.


The ovary consists of a mass of connective tissue containing ovarian follicles. Ovarian follicles are the immature eggs (ova) and their surrounding tissues.

As the egg grows larger, the follicle enlarges and gets filled with fluid. This relatively large fluid filled sac, containing the maturing egg and its surrounding nutritive tissue is called the Graafian follicle. The follicle secretes the hormone-oestrogen. When the Graafian follicle is ripe, it projects from the surface of the ovary, bursts and releases the ovum into the funnel of the oviduct. The cilia lining the funnel helps pick up and push the released ovum into the oviduct.

Corpus luteum: The remnant of the ruptured follicle persists and converts into a yellow mass of endocrine tissue called the corpus luteum. The corpus luteum secretes the hormones oestrogen, progesterone and relaxin.


Fertilisation occurs if the released ovum meets with a sperm as it moves down the oviduct.

The site of fertilisation is the oviduct:

Sperms are produced and matured at the rate of 300 million per day. Once ejaculated, they have a life expectancy of about 48 hours. The sperm with its minutes head and whip-like tail, nine times as long as the head, propels itself with its thrashing tail. The sperms swim indifferently past the egg. Fertilisation in human beings is a chance, depending on a random sperm hitting the egg by accident. However, once a strike is made, the sperm holds on tenaciously. The lysosomal enzymes of the sperm cells digest the limiting membrane of the ovum and the entire sperm (head, body and tail) penetrates and enters the ovum.

Fertilization usually occurs within 24 hours of ovulation and the union of the male and female nuclei results in the formation of zygote.

Identical and Fraternal Twins

Identical twins are formed when one fertilised egg splits into two.

Each part develops into separate individuals but shares a common placenta. Identical twins bear a striking resemblance to each other. Identical twins are always of the same sex.

Faternal twins (or non-identical twins) occur when two separate eggs are fertilized at the same time, but by different sperms. Each egg develops independent of the other on individual placenta. Fraternal twins may be of the same sex or of opposite sex and they resemble or differ from each other as much as any other brother or sister who are not twins.


The fertilized egg contains only microscopic amount of food (starch, protein, sugar) which can barely last a week. The zygote, which has undergone cell division to form a hollow ball of cells called blastocyst now attaches (implants) itself to the roof of the uterus and draws nourishment from the mother.

The attachment of the blastocyst to the endomentrium (inner lining of uterus) 7-8 days after fertilization is called implantation.

The Sperm and Fertilisation

Composed of a head, midpiece and tail, the sperm is adapted to reach and penetrate the female ovum:

(1) The tail propels the sperm along its way.

(2) The midpiece has abundant mitochondria that provides the energy for locomotion.
(3) The head contains acrosome, a specialised lysosome that digests the limiting membrane of the ovum and facilitates penetration by the sperm.


The blastocyst is differentiated into

(1) Trophoblast: Outer covering of cells.

(2) Embryoblast: Inner mass of cells

(3) Blastocoele: Internal fluid filled

Functions of Placenta

(1) Transfers oxygen, nutrients, water and hormones from the mother to developing embryo.

(2) Transfers wastes from the embryo into the mother’s blood.

(3) Provides protection to embryo since most micro organisms from the maternal blood cannot pass through it into the embryo.
(4) Produces hormones like oestrogen, progesterone and relax in which are necessary to maintain pregnancy.

Embryonic and Foetal Growth

While the trophoblast forms the feeding layer, the inner cell mass changes from a solid mass of cells into a hollow organ, resembling a figure of eight, i.e. it contains two cavities separated by a double layered plate.

Embryonic disc: The middle plate of the hypothetical figure eight is called the embryonic disc. This alone develops into the human being.

Amnion: The upper half of the figure eight forms a water sac completely surrounding the embryo except at the thick umbilical cord. The embryo then floats in this water jacket (amniotic fluid) which acts as a shock absorber. The fluid protects the embryo against mechanical jerks or blows that may strike the mother’s body.

Yolk sac: The lower half of the figure eight becomes a small empty vesicle called the yolk sac. In the second month of development, it is cut away (severed) from the embryo.

Gestation: The period of intrauterine foetal development, i.e. the full term of development of the embryo in the uterus is called the gestation period.

In humans, the total gestation period is about 280 days (a little over 9 months) from the beginning of the last menstrual period.

Embryo: An animal growing in an egg or in its mother’s body is called an embryo. Hatching ends the embryonic stage in animals, other than mammals.

Foetus: In mammals, the stage when an embryo starts to have the appearance of a fully developed offspring is called a foetus. In humans, the embryo changes to a foetus after about two months of development.

Chromosome number in mature sperm and ova: A human body cell has 46 chromosome number. During spermatogenesis (sperm maturation) and oogenesis (egg maturation) the sperm and ova undergo meiosis or haploid cell division in which the chromosome number is reduced to half, i.e. each cell now has 23 chromosome number instead of 46.

Thus, when the sperm cell (23 chromosomes) fuses with the ovum (23 chromosomes), the zygote formed has 46 chromosome number like its parent.

The zygote then divides mitotically or by diploid cell division in which the chromosome number remains constant.


The excretory system in man consists of kidneys. They are a pair of bean shaped structure lying in the abdomen, one on each side of the vertebral column just below the diaphragm.

The left kidney is placed a little higher than the right kidney. In the inner surface of kidney is an opening called hilus through which blood vessels, nerves, lymphatic ducts and ureters enter or leave the kidney. The hilus, inside the kidney, expands into a funnel shaped are called pelvis.

There are two distinct regions that can be seen in the kidney an outer granular portion called the cortex and an inner medulla. In the cortex are present the malpighian bodies, which filter the waste products from the blood. The medulla portion contains the collecting ducts of nephrons and thus passes the urine to the pelvis of the kidney.

Each kidney is made up of numerous delicate uriniferous tubules or nephrons. Each nephron consists of two main parts:

(1) Malpighian body – it has a cupshaped depression called Bowman’s capsule in which tuft of capillaries called glomerulus are present. An afferent renal arterioie enters the capsule, divides into capillaries forming glomerulus and leaves as efferent renal arteriole.

(2) Secretary tubule starts after malpighian body and moves towards medulla making a U turn which is called loop of Henle and joins collecting ducts. These collecting ducts join to form a larger duct the duct of Bellini. In secretary tubule, various substances from the filtrate are reabsorbed back.

Ureters: From each kidney arises a thin muscular tube called ureter. It emerges out from hilum of each kidney. The two tubes bring the urine down to urinary bladder.

Urinary bladder: It is a single sac like structure in which urine is stored, both bladder and ureters are lined by transitional epithelium.

Urethra: The urinary bladder opens to the outside through a membraneous tube called as urethra. In female it serves as a passage for urine only. In male it functions as a common passage for urine and spermatic fluids. A muscular sphincter keeps the urethra closed except during voiding of urine.

Mechanism of urine formation

In man and other mammals, urea is the main excretory product and is removed by the nephrons of the kidney as urine. The following of urine involves the following steps:

1. Glomerular filtration: Glomerulus is a tuft of capillaries found in the Bowman’s capsule of the nephron. The lining of Bowman’s capsule has a single layer of flat epithelial cells through which blood is filtered into the lumen of the tubule.

The filterate formed in the tubule is known glomerular or nephric filtrate. The filteration in the glomerulus is a passive process and depends on osmotic pressure. A fall in pressure of blood will reduce the renal filteration.

2. Selective reabsorption: There is 170 litres of nephric filterate formed in one day but only about 1-5 litres of urine is passed out daily. It is because most of nephric filterate is reabsorbed back. Water is absorbed back by osmosis and are reabsorbed by the active transport, Glucose, amino acids and vitamin C are reabsorbed back into the blood by the active transport mechanism. They do not appear in urine.

3. Tubular secretion: Here materials like urea, creatine, uric acid and are added back to filtrate.

Functions of Kidney


  • Removes nitrogenous metabolic wastes
  • Removes excess salts and vitamins
  • Removes bile pigments
  • Removes excess water

Osmoregulation (Maintains water balance)

  • Regulates the osmotic pressure of the blood. If the osmotic pressure of the blood is higher than the boy cells, water is drawn out from the cells (into the blood) causing them to shrink. If the osmotic pressure of the blood is lower than the body cells, the cells absorb water from the blood and swell.

Regulates pH of the blood (Acid-base balance)

  • It modifies the rates of secretion of acid or alkaline phosphates when the blood becomes too acidic or alkaline.

Composition of Human Urine

Water – 95%

Salts – 2%

Urea – 2.6%

Uric acid – 0.3%

Traces of creatine, ammonia etc.

Colour-pale yellow, due to pigment urochrome.

pH -  ranges from 5.0 to 7.8 (slightly acidic)

Hemodialysis: Uremia is a condition in which urea levels of blood rises abnormally. It occurs in those patients whose kidney tubules do not function properly so that metabolic wastes start accumulating in the blood and they need to be eliminated frequently. This artificial removal of wastes is done by a process called hemodialysis.

The problem of increased urination is called dieresis. The substance that increases the formation of urine is termed as diuretics. E.g. tea, coffee and alcoholic beverages.

Excretory system

  • In sponges, waste products are drained out through their water canal system; in hydra, cells release waste products into the coelenterons.
  • Flame cells perform excretory function in the body of tapeworms.
  • Nephridia is the excretory organ in Annelids.
  • Prawns have Green Gland and insects possess Malpighian tubules organs of excretion.
  • Earthworm excretes ammonia when sufficient water is available, but eliminate urea instead of ammonia in drier environment.
  • Xenopus toad and lung fishes are normally ammonotelic but they tum ureotelic when lying immobile and dormant in moist air.
  • Amphibian larvae are ammonotelic, but switch over to ureotelic during adult terrestrial form.
  • Shark retain so much of urea in blood that their blood osmotic pressure approaches that of sea water, this minimizes water loss from their body.
  • In birds and reptile, ureters and the rectum open into a sac called Cloaca, which stores both urine and faeces and reabsorb water from them.

Osmoregulation by Kidney

  • When water intake of animal is very high, the urine excreted has to be hypotonic, urine needs to be Hypertonic, contrarily when there is threat of excessive water loss from the body, the urine needs to be Hypertonic.
  • Almost all vertebrate, including mammals can produce hypotonic urine, diluter and lower in osmotic pressure than blood.
  • The henle’s loop is largely responsible for concentrating the urine. It is found that greater the ability of an animal to excrete hypertonic urine, the longer and the Hente’s loop in its kidneys.
  • The permeability of DCT and collecting duct is under the control of a hormone called vasopressin or Antidiuretic Hormone (ADH).
  • When the water content of the body is more than what it needs, the walls of DCT and collecting tubules remain impermeable to water, so no water get re-absorbed, and ultimately large volume of hypotonic urine is eliminated.
  • When water content in the body is low, ADH is secreted and walls of DCT and collecting duct become permeable to water, thus water get reabsorbed.


Nutrition is the substance in total, from which an organism derives its energy to do work and other materials for its growth, development and maintenance of life.

There are mainly two modes of nutrition.

1. Autotrophic nutrition: It is the process by which organisms make their own food as done by all green plants and some forms of bacteria. The organisms making their own food are called autotrophs.

2. Heterotrophic nutrition: All animals (including man) and non green plants like fungi and some bacteria cannot manufacture their own food but depend on autotrophs for their food, this kind of nutrition is called Heterotrophic nutrition.

3. Saprophytic nutrition: In this the organisms release some juices to soften or digest the food and then absorbs the nutrients. Thus they decompose the dead organic matter into simpler substances e.g. Fungi (yeast, moulds, mushrooms) bread mould (Rhizopus).

4. Parasitic nutrition: In this organism depends upon other organism for its nutritional requirements eg Fungus Puccinia is a parasite on wheat cuscuta, a dodder plant grows on other plants, tape worms and round worms are parasites in human body.

5. Holozoic nutrition: Most of the free living animals including man exhibit holozoic nutrition. It consists of following steps ingestion, digestion, absorption and egestion.


The process of digestion is defined as the breaking down of complex and insoluble organic substances such as carbohydrates, proteins and fats into simpler and soluble substances like glucose, aminoacids and fatty acids, respectively, so that they can be easily absorbed into the body. This is essentially a hydrolytic process and is carried out by various enzymes.

Alimentary canal of mammals

Buccal cavity: Mouth leads into a buccal cavity. At the floor of buccal cavity a muscular tongue is present, it mixes saliva into the food. In man, there are 32 teeth of four different types.

2 incisors, 1 canine, 2 premolars, 3 molars.

Incisors are used for biting, canines for tearing, premolar and molars for grinding the food.

  • The last molar comes only at the age of 20 years and is called wisdom tooth.
  • The study of teeth is called odontology.
  • Birds, toads, turtles and certain insects have no teeth.
  • Whale is a mammal without teeth.

Salivasry glands: There are 3 pairs of salivary glands namely parotids, submaxillary and sublingual glands. Their secretion is collectively known as saliva that is poured into the buccal cavity.

The enzyme present in the saliva is known as salivary amylase that helps in the digestion of carbohydrates, while mucin helps in lubrication of food. Saliva contains an anti bacterial enzyme lysosyme that kills bacteria. The lubricated food then travels through pharynx and oesophagus and moves into stomach.

Stomach: It is somewhat S shaped and is divisible into three regions fundus, cardiac and pyloric. The stomach wall produces gastric juice which chiefly contains HCI, mucin and two protein digesting enzymes rennin and pepsin.

Ruminant animals have rumen, reticulum, omasum and abomasums as there stomach parts. From the oesophagus, the food first enters into rumen and then into reticulum. Both these parts have numerous bacteria and protozoan to bring about fermentation and digestion of cellulose. This fermented food called cud, goes back to mouth for cud chewing. When this is properly chewed, it moves to the third chamber and finally to the fourth as usual.

Small intestine: Stomach opens into small intestine, it has three parts duodenum, jejunum and ileum. Duodenum gets the common bile duct and pancreatic duct from gall bladder and pancreas, respectively. Ileum has projections called villi in its inner surface. In between villi is intestinal gland or cyrypts of lieberkuhn, which secretes istenstinal juice. Small intestine is the main region where digestion and absorption of food occurs.

Large intestine: It is wider than small intestine, it does not have villi. It has three regions caecum, colon and rectum. Caecum is a small pouch like structure and its main part is vermiform appendix, which is vestigial organ (inflammation of appendix causes appendicitis). Colon is thicker and larger. Rectum is last part of large intestine. In colon and rectum most of the water is reabsorbed.

Glands associated with Alimentary canal

Liver: It is the largest gland in the body lying immediately below the diaphragm. It weighs about 1.5 kg in adults. The cells of liver (hepatic cells) mainly produce the bile juice that contains bile pigments and bile salts. These bile salts help in the digestion and absorption of fats. Bile juice does not contain any enzyme. Bile juice flows out of liver through hepatic ducts and flows into duodenum only when there is food in duodenum other wise the bile juice is stored into gall bladder.

Bile juice flows into gall bladder through the cytic ducts. Gall bladder is a sac located under the liver. Horse does not have a gall bladder.

Pancreas: It is made up of a large number of rounded groups called acinus which are held together by little connective tissues. The cells of an acinus produces Pancreas juice that has large number of enzymes.

Digestion of carbohydrates

  • Vertebrates have no enzyme to digest cellulose. They have to depend on symbiotic digestion by micro-organisms.
  • Man and animals consume carbohydrates mainly in the forms of starch e.g. cereals, fruits, tuber. Also consume sucrose (sugarcane), lactose (milk).
  • Man secretes starch hydrolysing enzyme in saliva, ptyalin.
  • Ptyalin is absent in saliva of many animals e.g. cow, buffalo, lion, and tiger.
  • Pigs secrete ptyalin in saliva.
  • About 30 per cent of food starch is hydrolysed in the mouth.
  • It you chew a piece of bread slowly, it will taste sweeter after some time. This is due to production of sweet tasting maltose from starch by ptyalin.
  • Gastric juice contains no carbohydrate.
  • Hyman being is the only mammal who ingest significant amount of lactose in milk even as an adult.
  • The digestibility of bread is increased by toasting because some of its starch is broken into dextrins during the process.
  • In Ruminants, cellulose fermentation is particularly facilitated by chewing of the cud.
  • In rats, guinea pigs and rabbits, fermentation and absorption of cellulose is not complete in one passage. So, they eat their faces (Coprophagy or excreta eating) containing much undigested cellulose.

Digestion of proteins

  • Hydrolysis of proteins does not occur in mouth.

  • But if uncooked natural proteins such as raw egg, unboiled milk or uncooked germinating gram is eaten then salivary water denatures the protein without hydrolysing it.
  • Protein digestion starts in stomach.
  • HCL not only provide acidic pH in the stomach for optimum Pepsin action, but also denatures many food proteins and destroy bacteria.
  • Digestion of milk protein Casein is initiated in stomach. Pepsin hydrolyses casein into paracasein, which is precipitated.
  • Trypsin act best at an alkaline pH. Trypsin is unable to hydrolyse casein, but it coagulate blood.
  • Chymotrypsin is an important milk coagulating enzyme.

Digestion of Fats

  • Lipases are enzymes for hydrolysing fats and oils.
  • Fats are largely digested in the small intestine.
  • Bile salts are of prime importance in the digestion of fat.


  • Most of the digested nutrients are absorbed in higher animals from the small intestine. Main site of absorption is in the ileum.
  • The presence of villi in small intestine and microvilli on free surface of epithelial cells considerably enhance the absorptive capacity of small intestine.
  • Absorption across plasma membrane of intestinal cells depends on two types of processes physical process such as Diffusion and Osmosis and energy dependent active process.

Balanced Diet

  • A diet is balanced if it contains all the nutrients in the correct amount.
  • Again, a balanced diet is related to the state of one’s age, health and occupation.
  • Carboydrates, proteins, fats, vitamins and minerals are Nutrients.
  • Carbohydrates and fats: provide energy.
  • Proteins: growth and repair of cellular mechanism.
  • Vitamins and minerals: aid vital reactions in cells and tissues.
  • Roughage: proper digestion.
  • For Pregnant woman and children protein requirement is high.
  • For hard working adults carbohydrates and fats requirement is high.


  • Carbohydrates are more suitable for the production of energy in the body than proteins and fats because carbohydrate molecules contain relatively more oxygen than the others.
  • Carbohydrates are supplied to the tissues mainly as blood sugar.
  • Carbohydrates are also stored in the tissues as glycogen.
  • Athletes, labourers doing heavy work and mountaineers should live on high – carbohydrate diet.
  • Wheat, rice, maize, sorghum, oat, barley, are rich sources.
  • 1 gm yield 17 KJ or 4.1 k cal.
  • Carbohydrates account for 60-80% energy requirement.
  • Sucrose – cane sugar, fructose fruit sugar.
  • Maltose – malt sugar
  • Test of starch: Iodine is used (blue-black colour confirms the test).
  • Test of Sugar: Benedict solution is used.


  • Fats gives twice energy than carbohydrates because it contain less oxygen.
  • 1 gm fat oil give 37 kg or 9.45 k cal.
  • Butter, ghee, cheese, milk, egg yolk, nut, meat are rich source of fat.
  • Fat is insoluble in water and soluble in organic solvent.
  • Fat stored as lipid in our body.
  • Few fats cannot be synthesised by our body and are called Essential fats. The most important of these is Unoleic acid (all vegetable oil contain, except coconut oil).
  • Unsaturated fat: low melting point, more reactive.
  • Saturated fat: Occur mostly in animal fat, high melting point, solidify at room temperature.


  • The principal nutritional role of proteins is to build tissue structure.
  • Some of the proteins cannot be synthesised in the animal body and must be supplied with food in adequate amounts. They are called Essential Amino Acid. Other amino acids may be synthesised in the body, are called Non-essential Amino Acid.
  • Eight amino acids are considered essential for human nutrition. These are methionine, theronine, tryptophan, valine, leucine, isoleucine, lycine and phenylalanine.
  • Plant proteins are frequently deficient in one or more essential amino acids. They are considered nutritionally inferior to animal proteins with respect to essential amino acid.
  • Linoleic, linolenic and arachidonic acids are essential fatty acids.
  • Groundnut, beans, cereals (maize and wheat), pulses are source of plant proteins.
  • Keratin is required for growth and repair of – skin and hairs, collagen is required for growth and repair of – cells and tissues.
  • 1 gm protein give 34 KG or 5.65 k cal.


  • and helps to retain water in the ECF and the cells, respectively, and maintain the normal fluid balance between extracellular and intracellular fluids. They increase excitability of nerves and muscles.
  • is essential for blood coagulation, neuromuscular function, cardiac function and action of many enzymes and hormones.
  • Phosphate help to maintain normal blood pH.
  • and selenium are required for the activities of different enzymes.
  • Copper helps in utilization of iron. Therefore, copper deficiency may produce anaemia.
  • is a constituent of carbonic anhydrase and enzymes.
  • Fluorine maintains normal dental enamel and prevents dental cavity.
  • First man made cereal is Triticosecale (Rai + Wheat).
  • Milk is rich source of all vitamins except vitamin C.
  • Vitamin D (skin) & K (liver) can be synthesised by our body.
  • Deficiency of proteins, carbohydrates and fats results in ‘protein – energy – malnutrition’.
  • Protein deficiency – Kwashiorkar, Marasmus.

Energy requirements of the Body

  • 5 years – 6000 KJ

Adult – 9,600 KJ

  • 11 years – 9000 KG

Adult – 12,000 KJ

  • 18 years – 11,000 KG

Adult – 16000 KG

(very heavy work)

Animal Diseases


Pathogen responsible

Animals affected

Main symptoms

Foot and mouth disease

Rinderpest (Cattle plague)

Blue tongue

Cow pox (vaccinia)

Ranikhet disease

(New castle disease)

Fowl paralysis

Fowl plague

Fowl pox


Anthrax (Splenic fever)

Blackquarter (black leg)


Johne’s disease

Brucellosis (Bang’s disease)


Foot rot

Haemorrhagic disease

Fowl typhoid







Virus (transmitted by mosquitoes)

Vaccinia virus





Bacteria (transmitted by infected milk and milk products)

Anthrax bacillus

Bacteria: Clostridium chauvoei

Bacteria: Streptococci and Staphylococci

Bacillus paratuberculosis

Bacteria: Brucella

Salmonella dublic and Styphimuriam

Bacteria: Fusiformis nodosus

Bacteria: Pasteurella multocida

Salmonella gallinarium

Mould (fungus) Microsporon,

Trichophyton Epidermophyton

Protozoan: Trichopmonas foetus (Transmitted through coitus)

Protozoan: Eimeria bovis

Protozoan: Trypanosoma congolense

Cattle, buffaloes, swine, sheep and goats

Cattle, sheep and goats

Cattle, sheep


Chickens and other domestic and wild birds


Chickens, domestic and wild birds

Chickens and other birds



Cattle and sheep



Cattle, sheep, goat and even man

Cattle and man


Cattle and sheep

Chicken and other domesticated birds

Cattle, sheep goat

Cattle, sheep, pig


Cattle, sheep, goats, camels, and dogs

Running sores in the mouth and between the toes. Reduced milk flow and loss of body weight.

Fever, ulcers in the mucous membrane of alimentary tract causing severe diarrhoea. Discharges from mouth, nose and eyes.

High temperature (104 C to 108 C). Haemorrhagic inflammation of buccal mucosa. Cyanosis (blue appearance) and swelling of the tongue.

Eruption of papules and pustules on the udder and teats.

Loss of apetite, diarrhoea and respiratory symptoms (suffocation) and finally paralysis.

Paralysis of legs and wings. Development of lymphoid tumours.

High temperature, oedema of the head, nasal and rapid death.

Wart-like nodules on the comb and wattle, blisters on the skin; eyes, nose and mouth covered by a yellow cheese like discharge.

Symptoms vary according to the organ involved. Continuous fever with dry husky cough, general emaciation. Intestine – persistant diarrhoea. Udders glands enlarged, milk rendered thin and watery.

Fever; vesicles on the skin. Swelling on the body and neck, reduction in milk secretion.

Fever and usually crepitant swelling of the infected muscle

Inflammation of mammary glands, i.e. swollen udders. Reduction of milk secretion; milk more watery.

Chronic dysentery, progressive emaciation and death in many cases.

Severe infection in uterus and testis leads to sterility; causes abortion in all these animals.

High temperature; diarrhoea with blood clots in stool.

A suppurative infection between the horn and the sensitive corium of the hoof of sheep causing lameness.

High fever, pneumonia and oedematous swelling of the skin.

Contagious scepticaemia disease.

Ring-shaped (rounded) surfy patches on the skin especially of neck and head.

Abortions, stillbirths, sterility and delayed conceptions.

Blood diarrhoea and emaciation.

Slow progressing anaemia, most destructive to adult cattle.

  • In kwashiorkor skin cracks and become scaly, abdomen swell, hair become reddish.
  • In Marasmus child show all the above symptoms besides wasting of muscles.
  • Disease restricted to given region and arising from its specific environmental conditions are called Endemic disease. Such as goiter in sub-Himalayan region.
  • Pellagra is common amongst people living on a maize diet, because maize interferes with the absorption of niacin in body.
  • Accumulation of fat soluble vitamins can be toxic. Disease caused by it called Hypervitaminosis.
  • Vitamin A accumulate in liver, while vitamin D promotes high absorption, which damage the kidney where it is deposited.

Plant Physiology & Anatomy


Respiration is a process of oxidation or breaking down of organic compounds, particularly simple carbohydrates like glucose, in the living cells, with the release of energy. In the absence of glucose, proteins and fat are first hydrolyzed and then oxidized.

Depending on whether oxygen is used in the process or not, respiration is of two types – aerobic and anaerobic.

(1) Aerobic Respiration: Aerobic respiration occurs in the presence of oxygen

One mole of glucose is completely broken down to yield carbon dioxide and water vapour with the liberation of 673 k cal of energy.

(2) Anaerobic Respiration: Anaerobic respiration takes place in the absence of oxygen and is represented by the under given equation.

It only involves a rearrangement of the atoms of glucose to form two molecules each of ethyl alcohol and carbon dioxide with the release of 21 k cals of energy. Therefore, the process is called intra-molecular respiration.

It is a normal process in certain microscopic bacteria and fungi. Fruits and seeds also may sometimes respire anaerobically. In most other plants, it is a temporary process and the ability possessed by plants to respire anaerobically is of tremendous survival value. Under adverse conditions, such as flooding when terrestrial plants are totally submerged in water, aerobic respiration is practically obstructed. The plants then respire anaerobically and hence survive.

Mechanism of Respiration

The process of respiration takes place in two steps called glycolysis and Kreb’s cycle.

(1) Glycolysis: An anaerobic process which takes place in the cytoplasm with the help of several enzymes. During this process, glucose is converted to pyruvic acid.

(2) Kreb’s Cycle: This is aerobic in character and takes place inside the mitochondria with the help of enzymes. During this process, pyruvic acid is converted into carbon dioxide and water vapour.


Transpiration is a physiological process during which water in the form of water vapour is lost from the internal tissues of plants, through the aerial parts of the plant. Maximum water loss takes place through the leaves since leaves offer a larger surface area more than stems and flowers for evaporation to occur.

Modes of Transpiration

Plants take up large amounts of water from the soil which pass into the internal parenchymatous tissues. The water from these cells is constantly evaporating and collecting in the intercellular spaces. This water diffuses out into the atmosphere by one of the following ways:

(1) Stomatal Transpiration: The epidermis of the leaf has numerous pores called stomata. These pores remain open during the day so that carbon dioxide of the air and diffuse in and enable the plant to prepare food by the process of photosynthesis. Simultaneously, water vapour from the cells diffuses out. Thus, transpiration accompanies photo- synthesis. It has been estimated that under ordinary conditions of light, temperature and humidity, almost 80-90% of transpiration takes place through the stomata.

(2) Caticular Transpiration: Some amount of water vapour also escape into the atmosphere through the thin cuticle covering the leaf surface. This is known as cuticular transpiration.

(3) Lenticular Transpiration: Stems of woody plants have openings on their surface called lenticels. Transpiration takes place through these openings since the lenticels are always open and the water vapour easily escapes through the loose mass of cells of each lenticle.

Manufacture of Food by Plant

Plants prepare food in the form of carbohydrates and proteins. Carbohydrates are the source of energy with which they carry out their vital activities. Proteins are essential for growth and repair by the synthesis of new protoplasm.

Catalytic role of Chlorophyll

(1) Chlorophyll becomes excited in the presence of light and initiates the process of photosynthesis.

(2) Even if the chlorophyll undergoes chemical or physical changes during the process of photosynthesis, it soon returns to its normal condition.

(3) The amount of chloroplast and its pigments in a leaf remains the same even after prolonged period of photosynthesis.

Manufacture of Carbohydrates:


Photosynthesis is a physiological process by which green parts of the plant, in the presence of sunlight, prepare food in the form of carbohydrates using carbon dioxide and water. Oxygen is released as a by-product.

Source of raw materials and energy for Photosynthesis

Raw materials

Carbon dioxide: Land plants absorb carbon dioxide from the air, which aquatic plants absorb carbon dioxide dissolved in water.

Water: Land plants absorb available water from the soil by the root system, while water plants absorb water from their aquatic surroundings.

Energy: The chloroplast traps solar energy and the light energy is converted into a high energy phosphate adenosine triphosphate or ATP.

Site of Photosynthesis

Photosynthesis can occur in any green part of the plant though it mostly takes place in leaves.

Mechanism of Photosynthesis

The overall reaction for photosynthesis is represented by the reaction shown alongside.

The process involves a series of complex photochemical reactions before the final products are obtained. It occurs in two stages. A part of the reaction takes place in the presence of light and one part proceeds in the absence of light. Accordingly, the two stages are known as the light reaction and the dark reaction.

Light Reaction

1. Photolysis of water: The radiant energy is absorbed by chlorophyll and transformed into chemical energy, which is capable of splitting the water molecule into hydrogen ion () and the hydroxyl ion (OH).

2. Production of Reducing Agent (): As a result of photolysis, hydrogen is formed, which is a reducing agent.

3. Production of Molecular Oxygen (): The hydroxide of water is oxidized to hydrogen peroxide, which decomposes to yield molecular oxygen under the action of the enzyme catalase.

4. Photophosphorylation: Conversion of low grade energy Adenoside diphosphate (ADP) into high potential chemical energy Adenosine triphosphate (ATP).

Dark Reaction

With the help of specific enzymes, the hydrogen formed during the light reaction is transferred to the carbon dioxide, and through a series of intermediate stages the final product glucose is formed. The energy required for the fixation of is also formed in the light reaction. The site of carbon dioxide fixation and reduction in the cell is the grana of the chloroplast.

Inter conversion of Glucose and Starch

Glucose, that is formed during photosynthesis, temporarily stored in the mesophyll tissues of the leaf in the form of insoluble starch. When photosynthesis ceases, the starch is converted into soluble glucose by the action of enzyme diastase and trans located to the storage organs. In the storage tissue, the glucose is again converted into starch by the leucoplasts. When required by the plant, the starch is reconverted into glucose. The inter conversion is independent of light and chlorophyll. Hence, it can occur in any part of the plant body.

Role of Elements in Plants

Potassium: A constituent of protoplasm.

Magnesium: Synthesis of chlorophyll.

Calcium: Maintains semi-permeability of protoplasm.

Iron: Synthesis of chlorophyll.

Sulphur: Constituent of an amino-acid cystine.

Phosphorus: Promotes nuclear and cell division.


Under anaerobic conditions certain micro-organisms like yeast convert sugar into alcohol and/or into simpler organic substance with the production of carbon dioxide and water vapour. This process which is similar to anaerobic respiration can be shown by the following equation.

Fermentation is of great commercial importance and is used in the manufacture of alcohol, acetic acid, lactic acid and a variety of commercial products.


The leaf can be defined as a lateral outgrowth of the stem arising from the node and having a bud in its axil. Leaves are flat, green and follow an acropetal order of development. Unlike stems, their growth stops on reaching maturity.

Venetion of lamina

Venetion is the arrangement of the veins in the lamina. It is mainly of two types:

1. Reticluate: In this type, the midrib give out branches, which further branch out and form a network. Dicotyledonous leaves usually show reticulate venetion.

2. Parallel: The leaf surface is covered by minute pores called stomata. These allow diffusion of gases to take place.Each stomata is surrounded by a pair of kidney-shaped, chlorophyll containing cells called the guard cells. These have the ability to contract and expand thereby regulating the opening and closing of the stomatal pore.

For instance, during very dry weather, the guard cells would contract making the stomata very small, thus preventing the water vapour from escaping. Stomata are generally open during the day and closed during the night. Stomatas are present in lower (ventral) surface of dorsiventral leaves.


Phyllotaxy is the arrangement of leaves on the stem or branch so that they avoid shading one another and the leaves get the maximum among of sunlight for photosynthesis.


Characteristics of a flower

The flower is a specialized shoot of limited growth. The flower is concerned with the sexual reproductive process in higher plants, leading to the formation of fruits and seeds. It arises in the axil of a leaf, or a leaf – like structure called the bract.

Position of Floral whorls on the Thalamus

The sepals, petals, stamens and ovary occur in a definite sequence on the thalamus. Based on the relative position of the ovary, this gives rise to three kinds of flowers.

(1) Hypogyny: The thalamus being generally conical or convex, the ovary occupies the highest position on the thalamus. The stamens, petals and sepals are separately and successively inserted below the ovary. The ovary is said to be superior, e.g. china rose, mustard, brinjal.

(2) Perigyny: The thalamus grows to form a cup-shaped structure enclosing the ovary but remaining free from it. The stamens, petals and sepals are attached to the rim of the floral cup. The ovary is said to be half inferior e.g. pulm, peach, pea, bean.

(3) Epigyny: The thalamus grows upwards, completely enclosing the ovary and fusing with it. The stamens, petals and sepals are borne above the ovary. The ovary is said to be inferior while the rest of the floral members are superior, e.g., spider lily, ground cucumber, sunflower, apple, pear.

Parts of a Flower

(a) Calyx: The calyx composed of sepals is usually green (sepaloid) and sometimes otherwise coloured (petaloid). It forms the outermost non-essential whorl of the flower and protects the flower in the bud stage.

(b) Corolla: The corolla forms the whorl inner to the calyx. Together with the calyx, it protects the inner essential whorls, the stamens and pistil. The petals of the corolla, like the calyx, may be united to each other or may be free. Being coloured it also attracts insects for pollination.

(c) Androecium: The androecium is the male reproductive whorl of a flower, inner to the corolla. It is composed of a number of stamens, each of which consists of a filament, anther and connective. The filaments may be free from each other and other structure or they may be fused with each other or fused with the petals or gynoecium.

(d) Gynoecium: The gynoecium or pistil is the female reproductive part of the flower and forms the innermost whorl. The pistil is composed of one or more carpels. If it is made up of more than one carpel, the carpels may be free or united together.


The arrangement of flowers on a twig is called inflorescence. Two main types of inflorescence are recognised.

(a) Racemose: In this type, the main axis never ends in a flower and continues to grow. Lateral flowers are formed in acropetal succession, i.e. youngest flower produced apically and older basally.

(b) Cymose: The main axis ends in a flower and so does the daughter axis. The youngest flower is formed basally, i.e. the progression of blooming is basipetal.


Fertilisation results in the development of the ovary into a fruit. Thus a fruit can be described as a ripened ovary.

It may be noted that many of the so called ‘vegetables’ like brinjals, tomato, lady’s finger, cucumber, peas, beans, etc., are in the true botanical sense, fruits.

Sometimes the ovary develops normally into a fruit without fertilisation. Such a type of fruit development is called parthenocarpy. Parthenocarpic fruits are almost always seedless as the banana and pineapple. Parthenocarpy can also be induced artificially by spraying the flowers with growth promoting hormones (called auxins), which results in the setting of fruits without fertilisation as in grapes, guava, and apples.

Classification of Fruits:

The chart given below gives a simplified categorisation of some of the important types of fruits:

Fruit (a ripened ovary)

True fruit

(Develops only from the ovary)

False fruit

(Develops from floral parts such as thalamus or calyx)


(Formed from a monocarpellary or multicarpellary syncarpous)


(Formed from the voeries of a multicarpellary apocarpous gynoecium. It is a collection of simple fruits)



Formed from an inflorescence


Thalamus is fleshy and fuses with the real fruit during development, e.g. apple


Fleshy e.g. berry, drupe

Etaerio of achenes, follicles, drupes, berries

Sorosis e.g. pineapple mulberry

Syconus e.g. fig banyan



Do not split along any suture (margin), e.g. achene, caryopsis cypsela, nut, samara

Split along one or more sutures or margins, e.g. legume, follicle capsule, siliqua


Pathology is the Study of Diseases and Diagnosis.

AIDS is a medical condition. A person is diagnosed with AIDS when their immune system is too weak to fight off infections. AIDS (acquired immune deficiency syndrome) is the final stage of HIV (Human Immuno Virus) infection, which causes severe damage to the immune system.

HIV is transmitted in many ways, such as anal, veginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth and breastfeeding. It can be transmitted by any contact of a mucous membrane or the bloodstream with a bodily fluid that has the virus in it, such as the blood, semen, vaginal fluid, preseminal fluid, or breast milk from an infected person.

Human immunodeficiency virus (HIV)

Is a lentivirus (a member of the retrovirus family). HIV infects vital cells in the human immune system such as helper T cells (specifically CD4+ T cells), macrophages, and dendritis cells.

A person is diagnosed with AIDS when they have developed an AIDS related condition or symptom, called an opportunistic infection, or an AIDS related cancer. The infections are called ‘opportunistic’ because they take advantage of the opportunity offered by a weakened immune system.

AIDS is the sixth leading cause of death among people ages 25-44 in the United States, down from number one in 1995.

The World Health Organization estimates that more than 25 million people worldwide have died from this infection since the start of the epidemic. In 2008, there were approximately 33.4 million people around the world living with HIV/AIDS, including 2.1 million children under age 15.

Antiretroviral treatment can significantly prolong the lives of people living with HIV. Modern combination therapy is highly effective and someone with HIV who is taking treatment could live for the rest of their life without developing AIDS.

Poliomyelitis is a vital disease that can affect nerves and can lead to partial or full paralysis. Also called Polio; Infantile paralysis; Post-polio syndrome. Spread from person to person, primarily via the fecal-oral route.

The virus is transmitted through contaminated food and water, and multiplies in the intestine, from where it can invade the nervous system. Many infected people have no symptoms, but do excrete the virus in their faeces, hence transmitting infection to others.

Initial symptoms of polion include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. In a small proportion of cases, the disease causes paralysis, which is often permanent. Polio can only be prevented by immunization. Anaemia is a condition in which the number of red blood cells or their oxygen-carrying capacity is insufficient to meet physiologic needs, which vary by age, sex, altitude, smoking and pregnancy status.

Iron deficiency is thought to be the most common cause of anaemia globally, although other conditions, such as folate, vitamin B12 and vitamin A deficiencies, chronic inflammation, parasitic infections, and inherited disorders can all cause anaemia.

In its severe form, it is associated with fatigue, weakness, dizziness and drowsiness. Pregnant women and children are particularly vulnerable.

Iron deficiency is the most common and widespread nutritional disorder in the world. As well as affecting a large number of children and women in developing countries, it is the only nutrient deficiency which is also significantly prevalent in industrialized countries. The numbers are staggering: 2 billion people – over 30% of the world’s population – are anaemic, many due to iron deficiency, and in resource poor areas, this is frequently exacerbated by infectious diseases. Malaria, HIV/AIDS, hookworm infestation, schistosomiasis, and other infections such as tuberculosis are particularly important factors contributing to the high prevalence of anaemia in some areas.

Food or waterborne diseases acquired through eating or drinking on the local economy:

Hepatitis A: viral disease that interferes with the functioning of the liver; spread through consumption of food or water contaminated with fecal matter, principally in areas of poor sanitation; victims exhibit fever, jaundice, and diarrhea; 15% of victims will experience prolonged symptoms over 6-9 months; vaccine available.

Hepatitis E: water-borne viral disease that interferes with the functioning of the liver; most commonly spread through fecal contamination of drinking water; victims exhibit jaundice, fatigue, abdominal pain, and dark colored urine.

Typhoid fever: bacterial disease spread through contact with food or water contaminated by fecal matter or sewage; victims exhibit sustained high fevers; left untreated, mortality rates can reach 20%. Vectorborne diseases acquired through the bite of an infected arthropod.

Malaria: caused by single cell parasitic protozoa Plasmodium; transmitted to humans via the bite of the female Anopheles mosquito’ parasites multiply in the liver attacking red blood cells resulting in cycles of fever, chills, and sweats accompanied by anemia; death due to damage to vital organs and interruption of blood supply to the brain; endemic in 100, mostly tropical, countries with 90% of cases and the majority of 1.5-2.5 million estimated annual deaths occurring in sub-Saharan Africa.

Dengue fever: mosquito borne (Aedes aegypti) viral disease associated with urban environments; manifests as sudden onset of fever and severe headache; occasionally produces shock and hemorrhage leading to death in 5% of cases.

Yellow fever: mosquito borne viral disease; severity ranges from influenza like symptoms to severe hepatitis and hemorrhagic fever; occurs only in tropical South America and sub-Saharan Africa, where most cases are reported; fatality rate is less than 20%.

Japanese Encephalitis: mosquito borne (Culex tritaeniorhynchus) viral disease associated with rural areas in Asia; acute encephalitis can progress to paralysis, coma, and death; fatality rates 30%.

African Trypanosoiasis: caused by the parasitic protozoa Trypanosoma; transmitted to humans via the bite of bloodsucking Tsetse flies; infection leads to malaise and irregular fevers and, in advanced cases when the parasites invade the central nervous system, coma and death; endemic in 36 countries of sub-Saharan Africa; cattle and wild animals act as reservoir hosts for the parasites.

Cutaneous Leishmaniasis: caused by the parasitic protozoa leishmania; transmitted to humans via the bite of sandflies; results in skin lesions that may become chronic; endemic in 88 countries; 90% of cases occur in Iran, Afghanistan, Syria, Saudi Arabia, Brazil, and Peru; wild and domesticated animals as well as humans can act as reservoirs of infection.

Plague: bacterial disease transmitted by fleas normally associated with rats; person to person airborne transmission also possible; recent plague epidemics occurred in areas of Asia, Africa, and South America associated with rural areas or small towns and villages; manifests as fever, headache, and painfully swollen lymph nodes; disease progresses rapidly and without antibiotic treatment leads to pneumonic from with a death rate in excess of 50%.

Crimean – Congo hemorrhagic fever: tick-borne viral disease infection may also result from exposure to infected animal blood or tissue; geographic distribution includes Africa, Asia, the Middle East, and Eastern Europe; sudden onset of fever, headache, and muscle aches followed by haemorrhaging in the bowels, urine, nose, and gums; mortality rate is approximately 30%.

Rift Valley fever: viral disease affecting domesticated animals and humans; transmission is by mosquito and other bitting insects; infection may also occur through handling of infected meat or contact with blood; geographic distribution includes eastern and southern Africa where cattle and sheep are raised; symptoms are generally mild with fever and some liver abnormalities, but the disease may progress to hemorrhagic fever, encephalitis, or ocular disease; fatality rates are low at about 1% of cases.

Chikungunya: mosquito-borne (Aedes aegypti) viral disease associated with urban environments, similar to Dengue Fever; characterized by sudden onset of fever, rash, and severe joint pain usually lasting 3-7 days, some cases result in persistent arthritis.

Chikungunya (in the Makonde language “that which bends up”) virus (CHIKV) is an insect-borne virus, of the genus Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. Symptoms of the disease include a fever up to 40C (104F), a petechial or maculopapular rash of the trunk and occasionally the limbs, and arthralgia or arthritis affecting multiple joints.

Water contact diseases acquired through swimming or wading in freshwater lakes, streams, and rivers:

Leptospirosis: bacterial disease that affects animals and humans; infection occurs through contact with water, food, or soil ontaminated by animal urine; symptoms include high fever, severe headache, vomiting, jaundice, and diarrhea; untreated, the disease can result in kidney damage, liver failure, meningitis, or respiratory distress; fatality rates are low but left untreated recovery can take months.

Schistosomiasis: caused by parasitic trematode flatworm Schistosoma; fresh water snails act as intermediate host and release larval form of parasite that penetrates the skin of people exposed to contaminated water; worms mature and reproduce in the blood vessels, liver, kidneys, and intestines releasing eggs, which become trapped in tissues triggering an immune response; may manifest as either urinary or intestinal disease resulting in decreased work or learning capacity; mortality, while generally low, may occur in advanced cases usually due to bladder cancer; endemic in 74 developing countries with 80% of infected people living in sub-Saharan Africa; umans act as the reservoir for this parasite.

Aerosolized dust or soil contact disease

Acquired through inhalation of aerosols contaminated with rodent urine:

Lassa fever: viral disease carried by rats of the genus Mastomys; endemic in portions of West Africa; infection occurs through direct contact with or consumption of food contaminated by rodent urine or fecal matter containing virus particles; fatality rate can reach 50% in epidemic outbreaks.

Irespiratory disease acquired through close contact with an infectious person:

Meningococcal meningitis: bacterial disease causing an inflammation of the lining of the brain and spinal code; one of the most important bacterial pathogens is Neisseria meningitides because of its potential to cause epidemics; symptoms include stiff neck, high fever, headaches, and vomiting; bacteria are transmitted from person to person by respiratory droplets and facilitated by close and prolonged contact resulting from crowded living conditions, often with a seasonal distribution; death occurs in 5-15% of cases, typically within 24-48 hours of onset of symptoms; highest burden of meningococcal disease occurs in the hyperendemic region of sub-Saharan Africa known as the “Meningitis Belt” which stretches from Senegal east to Ethiopia.

Animal contact disease acquired through direct contact with local animals:

Rabies: viral disease of mammals usually transmitted through the bite of an infected animal, most commonly dogs; virus affects the central nervous system causing brain alteration and death; symptoms initially are non-specific fever and headache progressing to neurological symptoms; death occurs within days of the onset of symptoms.

Age of the child

At Birth

6 weeks

10 weeks

14 weeks

6-9 months

9 months

15-18 months

5 years

10 years

16 years

Govt Schedule

BCG (Against Tuberculosis) OPV (Against Polio) This dose of vaccine at birth is called the zero dose.

OPV (first dose) DPT (Triple vaccine against diphtheria, pertusis and tetanus)

OPV (second dose) DPT (second dose)

OPV (third dose) DPT (third dose)


OPV (fourth dose) DPT (fourth dose)

DT (5th dose) (only for diphtheria and tetanus)

TT (against tetanus)


IAP Schedule

BCG, OPV HB (Against hepatitis B)

OPV (1st dose) DPT (1st dose) HB (2nd dose)

OPV (2nd dose) DPT (2nd dose)

OPV (3rd dose) DPT (3rd dose)

HB (3rd dose)


OPV (4th dose) DPT (4th dose) MMR (vaccine against Measles, Mumps and German Measles (rubella))

OPV (5th dose) DPT (5th dose) DPT (5th dose)



Diseases caused by Fungi


Pathogen responsible

Mode of transmission

Main symptoms of disease

Ringworm (tinea)

Microsporum, Trichophyton

Direct contact from unbathed cats, dogs or objects handled by infected individuals.

Sores begin as small, slightly raised reddish areas, enlarge, become redder and contain one or more blistered areas on skin and scalp. Cause partial and temporary baldness in children.

Athlete’s foot


Bad foot hygiene where skin remains warm and moist for long periods, fungi find optimum condition to invade dead outer layer of skin.

Painful itching or burning sensation in the infected areas. Crack appears in the skin at the base of 5th toe or between 4th and 5th toes, mass of loose dead skin clings between toes, otherwise reddening, scaling and thickening of skin between toes.

Madura foot

Maaurella mycetomi

Fungi gain entry through some minor injury to the skin.

Produce a chronic, granulating infection of the lower extremities, affected part becomes enlarged and develops many deep sores, extensive bone destruction leading to crippling deformities.

(Diseases Caused by Protozoans)


Pathogen responsible


Mode of transmission & incubation period

Main symptoms of disease



Passes thorough a developmental phase in liver, resides inside RBCs, and carried by blood to all organs

Transmitted to man by bite of an infected female anopheline mosquito

Three stages: Cold stage- headache, shivering and rising temperature: Fever stage- fever rises to its maximum, severe headache, pain in back and joints, vomiting; Sweating stage profuse sweating, fall in temperature, pain relieved

Amoebic dysentery or amoebiasis

Entamoeba histolytica

Large intestine

Transmitted from man to man through ingestion of cysts in drinking water, vegetables and food contaminated with faeces

Acute dysentery with blood and mucous in stools, and severe abdominal pain. Secondary complications include formation of multiple abscesses in liver, lung brain, spleen and ulceration of skin, vagina and penis.

Sleeping sickness (Trypan-osomiasis)

Trypanosoma brucei

Reaches lymph nodes via lymphatic blood and infects brain

Transmitted by bite of tsetse fly

Fever, severe headache, enlargement of glands at back of neck, rash on the back and chest, joint pains, swelling of eyelids, ankles and hands, trembling, loss of appetite, no desire to work except sit or sleep, mental disturbances, coma and death.

Kala-azar or black sickness

Leishmania donovani

Reticuloendothelial cells

Man becomes infected by bite of sandifly

Enlargement of spleen, liver, fever, jaundice, skin becomes dark through pigmentation

Diseases caused by Worms


Pathogen responsible & its habitat

Mode of transmission

Main symptoms of disease


Teenia solium; small intestine (jejunum) of man

Part of the life cycle in pig, man gets infected on eating pork, infected stage being mature cyst (cysticercus) in pork

Abdominal discomfort, chronic indigestion, anemia, diarrhea alternating who constipation

Ancylostomiasis or ‘Hook-worm disease’

Ancylostoma duodenale; small intestine (jejunum) of man

Transmission from person to person, filariform larvae passed out in faeces, man picks up infection walking barefoot on faecally contaminated soil,

Dermatitis; reddish, itchly papule along the path traversed by larvae; severe anaemia; duodenal ulcer, constipation. Patient pale, face puffy with swelling of lower eyelids, oedema of feet and ankle.


Ascaris lumbricoides; small intestine (jejunum) of man

Transmission from person to person, ripe eggs passed out in faeces, infection affected by swallowing ripe Ascaris eggs with raw vegetables.

Larvae in lung cause pneumonia. May give rise to typhoid-like fever, causes protein and Vitamin A deficiencies resulting in protein-calorie malnutrition and neighblindness respectively. Can cause appendicitis, jaundice by blocking lumina of appendix and bilary passages.

Enterobiasis or ‘Pinworm’ disease

Enterobius vermicularis; caecum and vermiform appendix

Transmission from one person to another by ingestion of eggs in contaminated food or drink. Autoinfection itching in anus; scratching anus and ripe eggs on fingers transferred to food ingestion of such food.

Eczematous condition around the anus, bed wetting at night, inflammation of vermiform appendix.


Wuchereria bacrofti; lymphatic vessels and lymph nodes

Part of the life-cycle in mosquito in which larvae develop and become infective to man, with mosquito bite larvae deposited on skin, which enter through puncture wound and reach lymphatic channels.

Elephantiasis i.e. enormous enlargement certain body parts such as that of leg, scrotum, penis, labia, clitoris, breast, forearm.

Last Updated on Wednesday, 02 May 2012 06:07