CBSE Class 9 Science Diversity in living Organism Exam Notes

This CBSE Class 9 Science exam notes page on Diversity in Living Organisms covers classification and taxonomy, the basis of classification, the hierarchy of classification groups, binomial nomenclature, the two, three, four, five and six kingdom systems, the characteristics of Kingdom Monera, Protista, Fungi, Plantae and Animalia, the plant divisions from Thallophyta to Angiosperms, the animal phyla from Porifera to Chordata, and the classes of vertebrates.

CLASSIFICATION

The method of arranging organisms into groups on the basis of similarities and differences is called classification.

TAXONOMY

Taxonomy is the study of diversity and kinds of organisms and the evolutionary relationships among them.

BASIS OF CLASSIFICATION

Some examples of such characters, used in grouping and sub-grouping of organisms, are as follows:

Cells are prokaryotic or eukaryotic
Organisms may be grouped into two broad categories on the basis of whether they possess prokaryotic cells or eukaryotic cells. In the case of prokaryotic cells the nuclei and other organelles are not clearly developed. Eukaryotic cells, on the other hand, have membrane-bound organelles, including a nucleus.

Cells occur singly or in clusters
Many organisms are unicellular, i.e., made up of only one cell, e.g., Amoeba. Others are multicellular, i.e., cells group together to form a single organism (e.g., insect). In the case of multicellular organisms the different groups of cells carry out specialized functions.

Organism is photosynthetic or takes food from outside
Green plants perform photosynthesis and synthesise their own food. Animals cannot perform photosynthesis. They get food from outside.

Organisation of different body parts
Grouping of organisms may be done on the basis of body organization. For example, plants possess stem, root and leaves. Similarly, animals possess specialized organs to perform different functions. The characteristics based on body design used for classification of plants are quite different from those used for classifying animals.

HIERARCHY OF CLASSIFICATION GROUPS

In classification, the organisms that closely resemble one another are placed in a group. These groups are further placed in larger groups on the basis of close similarities. The larger groups are again placed in still larger groups. The various grouping levels or ranks in classification are known as categories. Each category has its specific name. There are seven major categories:
1. Species
2. Genus
3. Family
4. Order
5. Class
6. Phylum (for animals) or Division (for plants)
7. Kingdom

Species
Species is the lowest category and is regarded as the basic unit of classification. It is a group of similar individuals which resemble each other in morphology, breed among themselves but not with others, and are probably descended from a common ancestor.

Genus
A genus is a group of closely resembling species having a common ancestry. All the species in a genus show similarities in broad features of their organization but differ in minor details.

Family
A family represents a larger group of closely related genera. It is composed of one or more genera. For example, the genus Felis of cats and the genus Panthera of lion, tiger and leopard are placed in the family Felidae because all these animals have retractile claws.

Order
An order is a group of closely related families. For example, the family Felidae (that includes cats) and the family Canidae (that includes dogs) are assigned to the order Carnivora because both cats and dogs have large canine teeth and are flesh eaters.

Class
A class is a group of related orders.

Phylum or Division
Phylum (in the case of animals) or Division (in the case of plants) is a group of related classes.

Kingdom
Kingdom is the highest category in biological classification. It is a group of phyla (in the case of animals) or divisions (in the case of plants).

The various categories used in biological classification can be arranged in a hierarchy, that is, ranked one above the other. It was introduced by Linnaeus and is, therefore, called the Linnaean hierarchy. The hierarchy indicates the various levels of kinship (i.e., relationship by blood). Nearer the categories in the hierarchy, the greater is the similarity between their organisms. The hierarchy of major categories is given below:

[Figure: Hierarchy of major categories drawn as a downward staircase, from top to bottom: Kingdom, Phylum/Division (for animals) (for plants), Class, Order, Family, Genus, Species]

BINOMIAL NOMENCLATURE

Binomial nomenclature was proposed by Carolus Linnaeus.
According to this system of nomenclature, each animal or plant is given two names: the first one is the generic name and the second one is the name of the species.
Scientific names are always in Latin.
The first letter of the generic name is always capitalized and that of the specific name is written in small letters. For example, the scientific name of frog is Rana tigrina, in which Rana is the generic name and tigrina is the name of the species.

TWO KINGDOM CLASSIFICATION

Carolus Linnaeus, the father of taxonomy, proposed the following two kingdoms.
Plantae: included Bacteria, Fungi, Algae, Mosses, Liverworts, Ferns, Conifers and flowering plants.
Animalia: included Protozoa, Sponges, Jellyfishes, Worms, Crabs, Insects, Millipedes, Centipedes, Spiders, Snails, Starfishes, Snakes, Frogs, Birds and Mammals.

THREE KINGDOM CLASSIFICATION

This was suggested by the German biologist E. Haeckel in 1866.
As some microscopic single-celled forms were unlike plants or animals altogether and could not be placed in the earlier system, a three kingdom system was proposed. It includes (1) Plantae, (2) Animalia, and (3) Protista. Protista contained all single-celled organisms like protozoans and unicellular algae.

FOUR KINGDOM CLASSIFICATION

This was developed by Copeland in 1966.
As prokaryotes (organisms without a true nucleus) were different from eukaryotes (organisms with a true nucleus), a new group, Monera, was formed.

FIVE KINGDOM CLASSIFICATION

This most favoured scheme was proposed by R.H. Whittaker in 1969. Fungi could not find a suitable place in the earlier systems of classification, and thus Whittaker's five kingdom classification found favour amongst most biologists.
This classification includes:
(a) Plantae
(b) Animalia
(c) Fungi
(d) Protista
(e) Monera

SIX KINGDOM CLASSIFICATION

It was proposed by Woese, Kandler and Wheelis (1990). They divided Monera into Archaebacteria and Eubacteria.

ORGANISMS

[Figure: Classification flow chart. ORGANISMS at the top branches into PROKARYOTES and EUKARYOTES. PROKARYOTES leads to MONERA. EUKARYOTES branches into UNICELLULAR and MULTICELLULAR. UNICELLULAR leads to PROTISTA. MULTICELLULAR branches into WITH CELL WALL and WITHOUT CELL WALL. WITHOUT CELL WALL leads to ANIMALIA. WITH CELL WALL branches into NON-GREEN AND DO NOT PERFORM PHOTOSYNTHESIS, which leads to FUNGI, and GREEN AND PERFORM PHOTOSYNTHESIS, which leads to PLANTAE.]

KINGDOM : MONERA (Gk. Monos - Single)

Kingdom Monera includes the most ancient, the smallest, the simplest and the most plentiful prokaryotes. These organisms are the most primitive. Monerans are characterized by the following:
- The organisms are mostly unicellular. The cyanobacteria are, however, filamentous.
- They do not have a definite nucleus. The genetic material is a circular, double-stranded, helical DNA (deoxyribonucleic acid) not enclosed by a nuclear envelope. Such organisms which do not have a definite nucleus are called prokaryotes.
- The cytoplasm is devoid of membrane-bound organelles, i.e., mitochondria, plastids, Golgi apparatus, lysosomes, endoplasmic reticulum, centrosome, etc. are lacking. However, ribosomes are present.
- Cell wall is generally present. Some prokaryotes do not have a cell wall.
- The mode of nutrition of organisms in this group can be either (i) autotrophic (i.e., synthesize their own food by photosynthesis) or (ii) heterotrophic (i.e., get their organic food from the environment).
- Single stranded flagella are present in many monerans.
Kingdom Monera includes true bacteria, actinomycetes, cyanobacteria or blue-green algae, mycoplasma and archaebacteria.

KINGDOM : PROTISTA (Gk. Protistos - First of all)

Kingdom Protista includes unicellular eukaryotic organisms. They are characterized by the following:
- Protists are mostly aquatic and live wherever there is water.
- The cell structure is typically eukaryotic. The protoplasm is surrounded by a distinct plasma membrane. In addition, some protists have an outer covering of pellicle, cuticle, shell or cellulose wall.
- The genetic material is linear, double-stranded, helical DNA, complexed with proteins and organized into distinct chromosomes. The chromosomes are enclosed by a nuclear envelope. Nucleolus is present.
- The cytoplasm contains membrane-bound organelles such as mitochondria, plastids, Golgi bodies, endoplasmic reticulum, ribosomes, etc.
- Their mode of nutrition can be autotrophic or heterotrophic.
- Motile protists move from one place to another with the help of pseudopodia, flagella or cilia.

Unicellular protists have been broadly divided into three major groups:
- The protistan algae, e.g., Euglena, diatoms
- Slime moulds
- Protozoan protists, e.g., Amoeba, Paramecium

KINGDOM : FUNGI

Fungi are mostly multicellular, non-photosynthetic organisms.
- Some fungi are microscopic while others can be seen with the naked eye.
- Some fungi are unicellular while others are multicellular, consisting of numerous filaments known as hyphae.
- The hyphae branch profusely and form a network called mycelium.
- Since fungi lack chlorophyll they cannot synthesise their own food, and therefore they either lead a parasitic or saprophytic life.
- Parasitic fungi may infect the host superficially or they may penetrate the host tissues (ectoparasite and endoparasite).
- Fungi develop haustoria, which help in absorption of nutrients from the host. Example: Mucor.

KINGDOM PLANTAE AND ANIMALIA

Kingdom : Plantae (Plant Kingdom)

[Figure: Chart titled KINGDOM : PLANTAE. Plant body is not well differentiated leads to 1. THALLOPHYTA. Plant body is differentiated branches into: plants do not possess vascular tissue (i.e., xylem and phloem), which leads to 2. BRYOPHYTA; and plants possess vascular tissue (i.e., xylem and phloem), which branches into plants do not produce seeds, leading to 3. PTERIDOPHYTA, and plants produce seeds. Plants produce seeds branches into plants bear naked seeds, leading to 4. GYMNOSPERMS, and plants bear seeds inside fruits, leading to 5. ANGIOSPERMS.]

Division : Thallophyta (Algae)
The plants in this division are commonly called algae. The term "Algae" was coined by C. Linnaeus, which means "sea weeds". The division is characterized by the following:
- The division comprises the most primitive and simple plants, not differentiated into true roots, true stem and true leaves. Therefore, they are thalloid (thallus-like) and placed under the division Thallophyta.
- They are predominantly aquatic and occur in both marine (sea water) and fresh water habitats. However, some are terrestrial and grow in moist places.
- Algal cells possess photosynthesis. Thus, algae are photoautotrophs.
- Some algae have additional accessory pigments of other colours (such as red, brown, yellow, etc.), and accordingly they have been classified into different groups such as green algae, red algae, brown algae, etc.
- The plant body may be unicellular (Chlamydomonas, Chlorella), colonial (Volvox, Hydrodictyon), filamentous unbranched (Spirogyra, Ulothrix), filamentous branched (Chara, Cladophora), heterotrichous (Ectocarpus) or foliaceous (Laminaria, Ulva, Fucus, Sargassum).
- The reproductive organs are unicellular, non-jacketed gametangia. The contents of the reproductive structure are completely converted into spores or gametes.
- After fertilization, an embryo is not formed.

[Figure: Algae. A. Chlamydomonas, B. Chlorella, C. Volvox, D. Hydrodictyon, E. Ulothrix, F. Spirogyra, G. Zygnema, H. Coleochaete scutata. Figures I and J are not labelled in the PDF.]

Division : Bryophyta
The division Bryophyta (Greek word Bryon = moss; phyton = plant) includes the simplest and most primitive non-vascular land plants having an embryo stage in their life cycle.
- The plants are essentially terrestrial but require water at every step in the life cycle. They usually grow in moist and shady places, on the sides of ditches, ponds, pools and lakes, on the banks of streams, in damp soil and on wet hills. They are called amphibians of the plant kingdom.
- The main plant body is the gametophyte (haploid body responsible for producing gametes). It is a flat, green thallus and lacks true leaves and roots. Plants are fixed by means of hair-like rhizoids.
- The vascular tissues (xylem and phloem) are completely absent.
- Sex organs are multicellular. The male sex organs are antheridia and the female sex organs are archegonia.
- An embryo is formed upon fertilization. The sporophyte lives as a parasite over the gametophyte.
- Examples: Liverworts (Riccia, Marchantia), hornworts (Anthoceros) and mosses (Funaria, Polytrichum).

[Figure: Bryophytes. A. Bryophytes, B. Riccia, C. Marchantia, D. Pellia, E. Anthoceros, F. Funaria, G. Polytrichum, H. Pogonatum. Labels shown include apical notch, dorsal groove, thallus lobes, sporogonium, gemma cup, mid-rib, rhizoids, involucre, calyptra, capsule, seta, aerial stem, male branch, female branch, male head, leaves, scale leaves, axis and rhizoids.]

Division : Pteridophyta
- They are found mainly in shady or damp places.
- The plant body is made up of root, stem and leaves.
- They have a well-developed vascular system.
- These plants have no flowers and do not produce seeds.
- Sex organs are multicellular and jacketed by sterile cells.
- Club mosses: Selaginella, Lycopodium ("ground pine"). Horsetails: Equisetum. Ferns: Dryopteris and Marsilea.

Gymnosperms
The seeds produced by these plants are naked and are not enclosed within fruits.
(i) Cycadae, e.g., Cycas
(ii) Coniferae, e.g., Pinus, Ginkgo, etc.

Pteridophytes and Gymnosperms compared

Angiosperms
- Angiosperms are highly evolved plants, and they produce seeds that are enclosed within the fruit.
- The reproductive organs are aggregated in a flower.

[Figure: Angiosperms divide into Dicotyledonae (Dicots) and Monocotyledonae (Monocots).]

Dicotyledonae (Dicots)
- The seeds produced by these plants have embryos with two fleshy leaves, the cotyledons.
- Their leaves have reticulate venation, with a network of veins.
- The root system has a prominent tap root.
- Examples: Pea (Pisum sativum), potato (Solanum tuberosum), sunflower (Helianthus annuus), rose (Rosa indica), banyan (Ficus religiosa), neem (Melia indica), apple (Malus silvestris).

[Figure: Venation in leaves. Left leaf labelled Parallel venation, which is the pattern of monocots; right leaf labelled Reticulate venation, which is the pattern of dicots.]

Monocotyledonae (Monocots)
- The seeds of these plants have only one cotyledon.
- Their leaves have parallel venation.
- The root system consists of similar fibrous roots.
- The vascular bundles are scattered and closed (i.e., they lack cambium). Secondary growth does not occur.
- Examples: Maize (Zea mays), wheat (Triticum vulgare), rice (Oryza sativa), onion (Allium cepa), sugarcane (Saccharum officinarum), barley (Hordeum vulgare), banana (Musa), coconut and grasses.

Monocots and Dicots compared

Kingdom : Animalia (Animal Kingdom)

Characters of the Kingdom Animalia
- These organisms are multicellular, eukaryotic and without chlorophyll.
- The cells possess no cell walls and no plastids.
- Central vacuoles are absent, but small vacuoles may occur.
- Most of them are free moving (except sponges and some coelenterates).
- Nutrition is primarily ingestive.
- Reproduction is generally sexual and the haploid stage is represented only by gametes.
- Growth of the organism stops when the adult stage is reached.

[Figure: Kingdom Animalia chart by level of organisation. KINGDOM : ANIMALIA splits into Cellular, leading to 1. Porifera; and Tissue. Tissue level splits into Pseudocoelom present, leading to 4. Nematoda, and True coelom present. Coelom absent between epidermis and gastrodermis leads to Body radial, which gives 2. Coelenterata, and Body bilateral, which gives 3. Platyhelminthes. True coelom present branches into mesodermal cells formed from a single cell during growth of the embryo, which leads to 5. Annelida, 6. Arthropoda and 7. Mollusca, and endoderm gives rise to coelom. Endoderm branch splits into Notochord absent, leading to 8. Echinodermata, and Notochord present, leading to 9. Chordata.]

Phylum Porifera
- Sessile (stalk-less) and marine, except one group that lives in fresh water.
- Simplest multicellular, diploblastic animals.
- Organisation is at the cellular level (colony level). Cells are loosely held together and do not form tissues.
- Asymmetrical or radially symmetrical. Sponges may be vase-like, rounded, sac-like or branched.
- The body is perforated by numerous pores, the ostia, that open into a canal system with canals and chambers lined with collared flagellated cells called choanocytes.
- Examples: Sycon, Euplectella (Venus flower basket), Spongilla (fresh water sponge).

[Figure: Sycon, a vase-shaped sponge.]

Phylum Cnidaria (Coelenterata)
- Aquatic, mostly marine, a few such as Hydra are fresh water solitary or colonial forms.
- Cnidarians or coelenterates are multicellular, diploblastic animals with tissue grade of organisation.
- Body shows radial symmetry.
- They possess specialized cells (cnidoblasts) bearing stinging organelles called nematocysts. Nematocysts help to paralyse the prey by injecting poison or to hold the prey.
- They exhibit the phenomenon of polymorphism (e.g., Physalia).
- The body shows two main forms, the polyp and the medusa.
- Examples: Hydra, Obelia (sea fur), Aurelia (jellyfish), Metridium (sea anemone).

[Figure: Hydra.]

[Figure: Classification of Kingdom Animalia. KINGDOM ANIMALIA divides into Protozoa, with a single Protozoa box below it, and Metazoa. Metazoa divides into Parazoa, which contains Porifera, and Eumetazoa. Eumetazoa divides into Radiata, which contains Cnidaria and Ctenophora, and Bilateria. Bilateria divides into Protostomia and Deuterostomia. Protostomia divides into Acoelomata (Platyhelminthes), Pseudocoelomata (Aschelminthes), and Coelomata (Annelida, Arthropoda, Mollusca). Deuterostomia contains Echinodermata, Hemichordata and Chordata.]

Phylum Platyhelminthes
- Bilaterally symmetrical and dorsoventrally flattened animals.
- Body thin, soft, leaf-like or ribbon-like.
- The digestive cavity (when present) has a single opening, the mouth (anus is absent).
- Suckers and hooks are usually present.
- Circulatory and respiratory systems and skeleton are absent.
- The excretory system consists of blind tubules called protonephridia.
- Examples: Dugesia (planaria), Fasciola (liver fluke), Schistosoma (blood fluke), Taenia solium (pork tapeworm).

[Figure: Taenia solium, a long, ribbon-like tapeworm with a small head at one end.]

Phylum Aschelminthes or Nematoda
- They are parasitic or free-living.
- They are triploblastic, unsegmented and show bilateral symmetry.
- Body cavity is not a true coelom.
- Alimentary canal is complete.
- Sexes are separate.
- Examples: Ascaris (round worm), Enterobius (pin worm), Wuchereria (filaria worm).

[Figure: Ascaris lumbricoides, a long cylindrical roundworm.]

Phylum Annelida
- They occur in moist soil, fresh water and the sea.
- They are elongated, with a segmented body and bilateral symmetry.
- They are the first animals with a true body cavity (coelom).
- The body bears lateral appendages for locomotion in the form of chitinous setae or parapodia.
- Examples: Nereis (sand worm), Aphrodite (sea mouse), Pheretima (earthworm), Hirudinaria (cattle leech).

[Figure: Earthworm.]

Phylum Arthropoda
- The body is covered with a thick chitinous exoskeleton.
- Respiration is through the general body surface, by gills, air tubes (tracheae) or book-lungs.
- The body segments are grouped into two regions, cephalothorax (head and thorax together) and abdomen, or three regions, head, thorax and abdomen.
- Triploblastic, bilaterally symmetrical and metamerically segmented animals.
- Each body segment usually bears paired lateral and jointed legs or appendages.
- Examples: Palaemon (prawn), Daphnia (water flea), Limulus (king crab), Palamnaeus (scorpion).

[Figure: Prawn.]

Phylum Mollusca
- They have a soft, unsegmented body.
- The body is divided into three regions: head, visceral mass and ventral foot.
- The outer surface is covered by a hard calcareous shell.
- Respiration is by gills called ctenidia.
- The sexes are usually separate.
- Examples: Chiton, Pila (snail), Unio (fresh water mussel), Octopus (devil fish).

[Figure: Pila (snail).]

Phylum Echinodermata
- They are marine, gregarious (live in groups) and free-living animals.
- The shape may be star-like, spherical or elongate.
- The body surface is covered all over by calcareous spines.
- Aristotle's lantern is present for mastication.
- Their symmetry is radial in adults but bilateral in larvae.
- Tube feet for locomotion.
- The body is unsegmented.
- The body cavity is modified into a water-vascular system or ambulacral system, with tube-like outward extensions for locomotion, called tube feet.
- Examples: Asterias (star fish), Echinus (sea urchin), Holothuria (sea cucumber), Antedon (feather star).

[Figure: Star fish.]

Phylum Chordata
Chordates are characterized by the following basic features:
- A dorsal, hollow, tubular nerve cord.
- Notochord present.
- Gill slits in the pharynx.
- Tail behind the anal opening.
- Ventral heart.

[Figure: Chordata classification. CHORDATA divides into Acraniata and Vertebrata. Acraniata contains Hemichordata, Cephalochordata and Urochordata. Vertebrata divides into Agnatha and Gnathostomata.]

Sub-phylum Protochordata
- The sub-phylum Protochordata includes animals which are bilaterally symmetrical, unsegmented, triploblastic and have a body cavity or coelom.
- The animals belonging to Protochordata possess a notochord at some stage in the life history. This is a flexible rod that lies between the dorsal nerve tube and the gut.
- The notochord provides a place for muscles to attach. It increases internal support and locomotory power.
- Protochordates are usually marine, soft, and have worm-like or vase-like forms.
- Examples: Balanoglossus (acorn worm or tongue worm), Herdmania and Amphioxus.

[Figure: Balanoglossus (acorn worm or tongue worm).]

Sub-phylum Vertebrata
- The sub-phylum Vertebrata includes animals which are bilaterally symmetrical, triploblastic, coelomate and segmented.
- The animal body typically consists of four regions: head, neck, trunk and tail.
- The notochord is replaced partly or fully by a jointed vertebral column (backbone) in the adult. The body of vertebrates is characterized by a well-developed skeletal system that allows a special distribution of muscle attachment points for movement.
- Besides the vertebral column and internal skeleton, vertebrates have a well-developed nervous system (brain) and sense organs (eyes, ears and nose).
- Vertebrates have a complex differentiation of body tissues or organs.
- There are two pairs of appendages (fins or limbs).
- Respiration is by gills in lower aquatic vertebrates. Higher land forms have lungs for gaseous exchange.
- Sexes are separate.

The sub-phylum Vertebrata is divided into five classes:
- Class Pisces
- Class Amphibia
- Class Reptilia
- Class Aves
- Class Mammalia

Class Pisces
- The animals belonging to Pisces are commonly called fishes. They live exclusively in water.
- The skin of fishes is covered with scales or plates, which help these animals to live in water.
- The body may be long, laterally compressed and spindle-shaped, or dorsoventrally flattened and disc-shaped. It usually consists of a head, trunk and a muscular tail.
- The muscular tail and fins help them to swim in water and move from one place to another.
- Fishes are cold-blooded animals and their hearts have only two chambers, one auricle and one ventricle.
- Fishes obtain oxygen dissolved in water and breathe through gills.
- They are egg-laying animals. Fertilization is external.
Fishes are broadly grouped into three categories:
- Cyclostomata: round-mouthed fishes, e.g., hagfish, lamprey.
- Chondrichthyes: cartilaginous fishes, e.g., Scoliodon (dog fish or Indian shark), sting ray, electric ray (Torpedo).
- Osteichthyes: bony fishes, e.g., Labeo rohita (rohu), Hippocampus (sea horse), tuna, etc.

[Figure: Some cartilaginous fishes. A. Scoliodon (dog fish or Indian shark); B. Sphyrna (hammer-headed shark); C. Pristis (saw-fish); D. Torpedo (the electric ray); E. Sting ray.]

[Figure: Some bony fishes. A. Synchiropus (mandarin fish); B. Hippocampus (sea horse); C. Caulophryne jordani (angler fish); D. Exocoetus (flying fish); E. Labeo rohita (rohu); F. Anabas (climbing perch); G. Pterois volitans (lion fish).]

Class Amphibia
- In evolutionary terms, amphibians form the first group among the chordates to live out of water and to comprise the first four-legged (tetrapod) land vertebrates. They live on land but lay their eggs in water.
- Amphibians are vertebrates leading two lives.
- These cold-blooded animals live partly in fresh water and partly on land (in moist places).
- The skin is smooth or rough, moist, slimy, glandular and mostly without scales.
- The heart has three chambers.
- The body has a distinct head and trunk, with no neck.
- Two pairs of pentadactyl (five-digit) limbs are present. Digits or toes have no claws. Limbs may be absent in some cases.
- Examples: Ichthyophis, Amphiuma (congo eel), Salamandra, Ambystoma, Necturus, Rana (bull frog), Bufo (toad), Hyla (tree frog).

[Figure: Bufo (toad).]

Class Reptilia
- Cold-blooded, terrestrial or aquatic vertebrates with the body covered with dry, water-proof skin having horny scales or scute plates.
- The heart has three and a half chambers. Crocodiles have a four-chambered heart.
- The body varies in form and is usually divided into head, neck, trunk and tail.
- Limbs are tetrapodous, pentadactyl (five-toed) type, with clawed digits. Limbs are absent in snakes and some lizards.
- Tympanum is small and depressed.
- Teeth are present in all reptiles except tortoises and turtles.
- Examples: Kachuga (roofed terrapin), Testudo (land tortoise), Uromastix (sand lizard), Hemidactylus (wall lizard), Calotes (garden lizard), Draco (flying lizard), Chamaeleon, Cobra, etc.

[Figure: Cobra.]

Class Aves
- Warm-blooded, tetrapodous vertebrates (birds) with various flight adaptations.
- Size ranges from the smallest humming bird to the largest ostrich.
- The heart has four chambers.
- Horny scales persist on the feet, but feathers cover most of the body. Cutaneous glands are absent.
- The boat-shaped body is divisible into head, neck, trunk and tail.
- Fore-limbs are modified into wings for flight. Kiwis have vestigial wings.
- Examples: Gallus (chicken), Passer (house sparrow), Corvus (crow), Columba (pigeon), Psittacula (parrot), Pavo (peafowl), Eudynamys (koel), Bubo (owl).

[Figure: Passer (house sparrow).]

Class Mammalia
- Mammals are primarily terrestrial vertebrates. They occur in all sorts of habitats, from the polar regions to the tropics.
- The body is variously shaped and is generally divisible into head, neck, trunk and tail.
- The skin is glandular and mostly covered by a horny epidermal exoskeleton of hair.
- There are two pairs of pentadactyl limbs, variously adapted for various purposes.
- Respiration occurs only by lungs.
- The heart is four-chambered, having two auricles and two ventricles.
- Sexes are usually distinguishable externally.
- Mammals are mostly viviparous (alive-bearing). However, some are oviparous and lay eggs (e.g., platypus and echidna). Kangaroos give birth to very poorly developed young ones. They are characterized by having milk-secreting mammary glands in the females for suckling the young for some time after birth.
- Examples: Macropus (kangaroo), Bat, Rattus (rat), Oryctolagus (rabbit), Felis (cat), Panthera (lion, tiger, leopard), Canis (dog), Elephas (elephant), Balaenoptera (whale), Macaca (monkey), Homo (man), Pan (chimpanzee).

[Figure: Mammals. A. Ornithorhynchus (duck-billed platypus); B. Balaenoptera (the whale); C. Platanista gangetica (the dolphin); D. Odobenus (the walrus); E. Scotophilus (the bat); F. Rhinoceros; G. Equus caballus (horse); H. Pan (chimpanzee).]

FLOW CHART : PLANT GROUPS

[Figure: Flow chart titled Plants with blank boxes labelled a to h. Plants branches into Do not have differentiated plant body, which leads to box a; and Have differentiated plant body. Have differentiated plant body branches into box b, which leads to Bryophyta, and With vascular tissue. With vascular tissue branches into Do not produce seeds, which leads to box c, and Produce seeds, which leads to box d. Box d branches into box e, which leads to Gymnosperms, and Bear seeds inside fruits, which leads to box f. Box f branches into box g, which leads to Dicots, and Have seeds with one cotyledon, which leads to box h. Boxes a to h are blank in the PDF.]

Species
Genus
Family
Order
Class
Phylum (for animals)/division (for plants)
Kingdom

Father of taxonomy - Carolus Linnaeus. He preposed following kingdoms.

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