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Living organism are classified according to:

1. Habitat.
2. Type of food they eat.
3. Type of reproduction.
4. Similarities and differences in form and functions.

Living organisms are classified into various units of classification. The largest of these units is Kingdom. Each Kingdom is further divided into smaller groups. These groups are:

1. Phylum
2. Class
3. Order
4. Family
5. Genus
6. Specie

Carolus A. Linnaeous, a Swedish biologist, proposed a method of naming. He introduced two-word system of naming organism. According to this system the first word denote the genus of which organism belongs and second name indicates the specie name.

It is also customary to write first name with a capital letter and second name with the small letter.

The word virus means poison. They are so small that they can not be seen with the light microscope. They can be studied only under the electron microscope.

Virus are 10 to 100 times smaller than bacteria. Its size ranges from 17 to 450 mm.

Viruses occur in many different shapes. e.g., round, rod like and crystal like.

The body of virus consist of a central core of DNA and outer coat of protein.

From the evolutionary point of view they are considered to be on the border line of living and non-living things.

Property of reproduction and presence of DNA is a positive sign of life in viruses.

They can be crystallized. In crystal form they can be stored for an indefinite period of time, without any loss of reproductive ability. When crystallized virus placed under favorable conditions they again start reproducing.

Virus depend upon other organisms for their nutrition and invariably parasite on them.

They cause many diseases in man. For example, cold, polio, small pox and measles.

Where as in plants they cause damage to leaves of potato, tobacco, and cauliflower.

These are unicellular prokaryotic organisms.

They measure about one micron in size.

Most of them have no chlorophyll hence cannot manufacture their own food, so they are heterotrophic which may be parasitic or saprophytic. Some bacteria can manufacture their own food they are called antotrophic bacteria.

They are classified into various groups according to their shapes e.g., spherical are cocci, rod shaped are bacilli and spiral shaped are spirila.

Bacterial cell is surrounded by a cell wall. Inside the cell wall is present the cell membrane. Bacteria lack nucleus in their cell but possess DNA.

They are responsible for many animal and plant diseases. For example in man they cause plague, diphtheria, tuberculosis, tetanus, pneumonia and cholera.

Certain types of bacteria are useful and are used to convert milk into curd and cheese. Some bacteria convert sugar cane juice into vinegar.

Saprophytic bacteria play important role by decomposing dead animals and plants and in this process release salts and minerals into the soil, thus making the soil fertile. Some bacteria fix nitrogen of air in such compounds which can be used as nutrients by plants.

It is a unicellular green fresh water plant which is visible under microscope. From an evolutionary view point it is considered to be the simplest aquatic plant. It is spherical slightly elongated or pear shaped.

It is surrounded by the cell wall which is made up of cellulose. On its interior and it has an out growth called apical papilla.

A pair of flagella occurs on apical papilla. By the means of flagella it moves from one place to another.

Inside the cell wall there is a cell membrane which is made up of lipid bilayer and proteins.

It is the region of cell between cell membrane and the nucleus. The cytoplasm contain many structures. Following are some of them.

The chloroplast helps in synthesis of food by the process of photosynthesis.

Two contractile vacuoles are present in the cytoplasm at the base of flagella. They remove matter and excess of water from the body.

A spherical body called pyrenoid is present in the chloroplast. It is believed that carbohydrates are accumulated in this pyrenoid.

A red eye spot is present near the interior tip of the organism. It is very sensitive to light and helps plant to distinguish between bright light and

Cytoplasm contain a big nucleus which control all the function of the cell.

It is unicellular animal found in stagnant pools and ponds. It is microscopic in size measuring about 0.25 mm. It does not possess a definite shape because it lacks pellicle.

The structure of amoeba is very simple. Following are some important structures:

It is surrounded by a cell membrane.

Cytoplasm is very clear. It is differentiated into two parts. The outer portion which is clear and transparent is called ectoplasm. The inner viscous, translucent and granular part is called endoplasm. The endoplasm contain many food vacuoles of different size in contractile vacuole and spherical nucleus. Organelles such as endoplasmic recticulum and mitochondria are also present in the endoplasm.

The animal moves by producing finger like projections called pseudopodia. The pseudopodia are also used to capture food particles. Amoeba respire by exchanging gases with the surrounding water through its surface.

1. Fungi are plants which lack chlorophyll. They cannot manufacture their own food.
2. They may be parasites or saprophytes.
3. Fungi are composed of numerous thread like structure called hyphae.
4. In multicellular fungi the hyphal filament consist of many cells.
5. Some of fungi as yeast are unicellular and microscopic. Other fungi are large in size and visible with naked eye. Mucor, Rhizopus, Penicillin, Puccinca, Ustilago and Mushroom are common types of fungi.

Some of fungi are important from the economic point of view. Some fungi are useful e.g., penicillin is produced by them which is a famous medicine. Some take part in food production e.g., mushrooms.

Some fungi are harmful and cause diseases e.g., ring worm is a disease caused by a fungus.

1. Algae are green plants and occur in both fresh and sea water.
2. Except blue green algae the cells of other algae groups contain a nucleus.
3. Algae manufacture their food by photosynthesis.
4. Algae are both unicellular and multicellular.
5. There are about 20 thousand species of algae.
6. Algae have been classified into green algae, golden algae, brown algae, and red algae on the basis of pigments they have.
7. Almost 90 % of the photosynthesis occurring in the aquatic environment is due to algae.

1. They produce oxygen.
2. They provide food to animals.

• Chlamydomonas® unicellular algae
• Ulothrix and spirogyra® multicellular green algae

Plants are organisms which have chlorophyll and cell wall besides other characteristics. Plants are classified as flowering and non-flowering plants.

Non-flowering plants are classified into Bryophytes and Pteredophytes while flowering plants are classified into Gymnosperms and angiosperms.

1. They lack vascular tissue and are mostly found on rocks, walls, trees in wet and shady places.
2. Mosses and liverworts are representative members of bryophytes.
3. Their root like structure are known as rhizods.
4. Mosses play an important role in disintegration of rocks.
5. They are often used as manure.
6. They reproduce sexually as well as asexually.

1. Mosses are small plants more advanced than algae.
2. They do not possess true root, stems and leaves.
3. Their stem is usually unbranched and has very small green leaves spirally arranged on it. There is no mid rib in the leaf.
4. They are fixed to the soil by rhizoids.
5. Mosses are aquatic plants but grow in cool, moist and shady places on land.
6. They often form mats on the floor of the forest.

1. They are lower vascular plants.
2. Sporophytes is the main vegetative stage in the life cycle.
3. They sporophyte bear root, stem and leaves but flower and seeds are absent.

1. Ferns possess special tissues for conducting water, salts and food to different parts of their body.
2. They have well developed roots, stem and leaves.
3. They lack flower fruit and seeds.
4. They are antotrophic.
5. Ferns are adapted to live in cold, humid and shady places.
6. Some of them live in water while others grow on shady hills or even on dry mountain tops.

1. Plants included in this group produce seeds like ordinary flowering plants.
2. Their seeds are not enclosed in fruits as in flowering plants, they are called gymnosperms.
3. Gymnosperms are usually tall woody trees.
4. These trees live for many years.
5. They remain green through out the year, they are also known as ever green plants.
6. These trees are found in colder regions at high altitude.
7. Their leaves are long and needle like.
8. Conifers is a subgroup of gymnosperms. Seeds of conifers are present in hard woody scales arranged to form cone. Therefore these plants are called conifers. These trees produce timber, gum, turpentine oil and dry fruits like chilgoza.
9. Examples of gymnosperms are cedars (deodar), paius (chir), cupressus and jhuja.

1. Seeds of angiosperms are enclosed in fruits.
2. They bear flower as the organ of reproduction.
3. The angiosperms are the most diverse and abundant group of plants.
4. The leaves of angiosperm plants are usually broad and flat.
5. Flowers may be unisexual or bisexual.
6. Pollination takes place through wind and insects.
7. Angiosperms have been divided into two classes on the basis of structure of the seeds. (a) Monocot, (b) Dicot.

They have two cotyledons in their seeds. e.g., sheesham, almond, peach, apple, pear, plum and mango.

They have one cotyledon in their seeds. e.g., grass, wheat, rice, maize, sugar cane and bamboo.

Animal kingdom is also a very diverse group ranging from simple animal to such complex mammals as humans. This kingdom is divided into two sub kingdoms depending upon presence or absence of backbone. Those which do not possess backbone are called invertebrates and those which have it are called vertebrates.

The number of invertebrates in nature is far greater than the numbers of vertebrates. Many invertebrates have no skeleton. Some have exoskeleton and few have endoskeleton. Following are the important phylums of invertebrates.

1. Protozoans are smallest animals as their body consist of single cell.
2. They may be free living or parasite.
3. Some protozoan parasites cause different diseases like malaria, dysentery etc.
4. Some of them are marine and they secrete calcareous shell around them.
5. Free living protozoans are amoeba, paramecium and euglena.

1. Body contains cavity, or system of cavities connected to exterior by pores.
2. Cavity lined by flagellated cells for creating water current.
3. Exoskeleton is calcareous, siliceous or horny spicules.
4. Always sessile.
5. Little intercellular integration and coordination. Body virtually a colony of single cells.
6. No sensory or nerve cells.

Simple sponge with uniform body wall.

More complex sponge with folded body wall.

1. They have sac like body cavity also serve as gut cavity (entron).
2. Mostly they are radially symmetrical i.e., section passing through any diameter give two opposite halves.
3. Body wall contains two layers of cells. (biploblastic).
4. The outer layer of cells is ectoderm and the inner layer of cells is endoderm separated by non-cellular mesogloea.
5. They exist in two forms polyp and medusa which in typical coelentrata life cycle, alternate with each other.
6. Tentacles bear explosive cells (nematobalast).

• Hydra
• Flelia
• Physalia
• Jelly fish etc.

1. Metamenic segmentation is exhibited by more structures and organ systems than in virtually any other phylum.
2. Externally metamerism shows itself in constrictions between successive segments , hence the name of the phylum.
3. Segments are separated by sheet like septa.
4. In most annelids each segment bears bristle like cheatae.
5. Segmented nephridia for excretion and osmoregulation.
6. Typically there is trochophore larva during development.

• Earthworm
• Leech
• Nasius

1. Ventral side of the body has soft muscular foot.
2. On the dorsal side there is a visceral hump containing the main digestive organs.
3. Visceral hump generally protected by shell.
4. Most molluscs have a rasping tongue like radula for feeding.
5. Gills for respiration.
6. Majority have lost all traces of metameric segmentation.

• Snail
• Octopus
• Squid

1. Body is flattened dorsoventrally (hence name of the phylum).
2. Possess a mouth but no anus.
3. Gut generally has numerous blindly-ending branches.
4. Flame cells are for excretion and osmoregulation.
5. Phylum contain many important parasites.

• Tape worm
• Planaria
• Liver flake

1. They have narrow body, pointed at both ends.
2. They are rounded in cross section.
3. They possess thick elastic cuticle.
4. The phylum contain many important parasites.

Large worm up to 20 cm long.

Small but destructive gut parasite.

1. Body is covered by chitinous cuticle, hardened to varying degree.
2. Jointed appendages are present.
3. Muscles are attached to cuticle which function as an exoskeleton.
4. Cuticle shed periodically (moulting, ecalysis) to allow for growth.
5. Body cavity is blood filled, haenocoel, derived from blastocoel.
6. Coelom much reduced.
7. Metameric segmentation as in annelid but segments not separated from each other by septa.
8. Some groups have compound eyes for vision.

• Mosquito
• Flies
• Spider
• Centipede
• Millipede

1. Their skin contain calcareous ossicle and spines.
2. They are exclusively marine.
3. Rentaradiate in adult stage, but larva is bilaterally symmetrical.
4. Mouth generally on lower side.
5. Move slowly but concerted action of numerous sectorial tube feet.
6. No proper circulatory system.

• Star fish
• Brittle star
• Sea urchin
• Sea cucumber

Notochord replaced in adult by vertebral column (backbone), brain enclosed in cranium (brain case). Vertebrates have been divided into five major groups.

• Fishes
• Amphibia
• Reptilia
• Aves
• Mammalia

1. These are entirely aquatic animals.
2. Body is spindle shaped.
3. Body consist of head, a trunk and tail.
4. In most cases the body is covered with scales.
5. They possess fins for swimming.
6. Respiratory organ are gills.
7. These animals are cold blooded.

• Sharks
• Rays
• Dog fish
• Rohu
• Trout etc.

1. They can live both on land and under water.
2. They have simple sac like lungs.
3. They have moist skin used as supplementary respiratory surface.
4. They breed in water.
5. Fertilization is external.
6. Aquatic larva (tadpole) undergoes metamorphous into terrestrial adult.
7. Gills are present in larva and lungs are present in adult.

• Newts
• Salamanders
• Frogs
• Toads

1. Mainly terrestrial.
2. Dry skin with scales.
3. Respiratory organs are lungs.
4. Fertilization is internal.
5. Eggs laid on land enclosed in shell.
6. Cold blooded animals.

• Lizards
• Snakes
• Crocodiles
• Alligators
• Turtles etc.

1. Body is covered by feathers.
2. Forelimbs are wings.
3. Toothless jaw covered with horny beak.
4. Warm blooded animals.
5. Larynx is sound producing organ.

• Ostrich
• Gulls
• Kiwi
• Pigeon etc.

1. Body is covered with hairs.
2. They possess mammary glands.
3. They are warm blooded animals.
4. They are divided into three large subgroups.

• Egg laying mammals
• Pouch mammals
• Placental mammals (true mammals)

These mammals lay eggs like the reptiles but feed their young ones on milk.

• Duck bill
• Spiny ant eater

These mammals give birth to underdeveloped babies. Since they are weak, the mother keeps them in a pouch on its belly until they develop fully and become strong.

• Kangaroo
• Opossum
• Koala bear

1. These mammals, the baby completes its entire development in the body of mother.
2. After birth the youngs are fed on mother’s milk.
3. These mammals have been divided into many subgroups.

These mammals come out at night and feed on insects.

• Hedgehog
• Shrews
• Moles

In these mammals the front teeth are absent very small. They have long nails with the help of which they dig earth. They fed on ants with the help of their long tongue.

• Armadillo
• Pangolin

These mammals have well developed cutting teeth in the form of long curved front teeth.

• Rabbit
• Squirrel
• Rat
• Porcupine

In these mammals the skin between the front limbs and hind limbs is drawn out to form pair of membranous wings for flying.

• Bat

These mammals have highly developed brain. They posses a high degree of intelligence.

• Monkeys
• Chimpanzee
• Man

These mammals eat flesh of other mammals. The tearing teeth (canine) are very strong and curved.

• Cat
• Dog
• Lion

These are the mammals which possess hoofs and are herbivorous.

• Goats
• Buffalo
• Horse
• Cow

They are the largest mammals living on land. They have large trunk or proboscis.

• Elephant

Theses mammals are not fish and permanently live in water. They never come on land. They are mostly marine and are the large aquatic animals. There forelimbs and hind limbs are modified into oar-like fins for swimming.

• Dolphin
• Whales

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