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Animalia

 Aquatic Animals Aquatic animals may be fresh water or marine. The animals living in open water or sea are called pelagic. They are of two types, plankton (= zooplankton, drifting with water currents, e.g., invertebrate larvae, small invertebrates) and nekton (= necton, actively swimming even against water flow, e.g., fishes). The animals living at the bottom are called benthon (e.g., Star Fish). Other terms are: Neuston - floating or swimming in surface water. Seston -living or nonliving, floating or swimming in water. Tripton-nonliving seston. Neritic -in coastal waters. Sedentary (Sessile)-animals fixed to substratum. Sedentary animals can be epizoons (over other animals), periphytons (attached over rooted plants) or epiphytic, epilithic (on rocks, stones), etc. Benthon may be sedentary or motile. Terrestrial Animals They live on land. Fossorial-in burrows, e.g., Rabbit. Animals resting in burrows are subterrestrial. Arboreal- on trees, e.g., Monkey. Scansorial- adapted to climbing, e.g., Wall Lizard. Cursorial-Running, e.g., Horse. Flying/Aerial- Winged, e.g., bird. Cave Dwelling. Living in caves. Nocturnal. Coming out or active during night. Diurnal. Coming out or active during day time. Crepuscular. Coming out in twilight. Vespertine. Coming out during evening. Auroral. Coming out at dawn. When you look around, you will observe different animals with different structures and forms. As over a million species of animals have been described till now, the need for classification becomes all the more important. The classification also helps in assigning a systematic position to newly described species.

Basis of classification
Inspite of differences in structure and form of different animals, there are fundamental features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems. These features are used as the basis of animal classification and some of them are discussed here.

Levels of Organisation
Though all members of Animalia are multicellular, all of them do not exhibit the same pattern of organisation of cells. For example, in sponges, the cells are arranged as loose cell aggregates, i.e., they exhibit cellular level of organisation. Some division of labour (activities) occur among the cells. In coelenterates, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues, hence is called tissue level of organisation. A still higher level of organisation, i.e., organ level is exhibited by members of Platyhelminthes and other higher phyla where tissues are grouped together to form organs, each specialised for a particular function. In animals like Annelids, Arthropods, Molluscs, Echinoderms and Chordates, organs have associated to form functional systems, each system concerned with a specific physiological function. This pattern is called organ system level of organisation. Organ systems in different groups of animals exhibit various patterns of complexities. For example, the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth and anus, and is hence called incomplete. A complete digestive system has two openings, mouth and anus. Similarly, the circulatory system may be of two types: (i) open type in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it and (ii) closed type in which the blood is circulated through a series of vessels of varying diameters (arteries, veins and capillaries).

Symmetry
Animals can be categorised on the basis of their symmetry. Sponges are mostly asymmetrical, i.e., any plane that passes through the centre does not divide them into equal halves. When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry. Coelenterates, ctenophores and echinoderms have this kind of body plan (Figure 4.1a). Animals like annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry (Figure 4.1b). Diploblastic and Triploblastic Organization
Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g., coelenterates. An undifferentiated layer, mesoglea, is present in between the ectoderm and the endoderm (Figure 4.2a). Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals (platyhelminthes to chordates, Figure 4.2b). 4.1.4 Coelom Presence or absence of a cavity between the body wall and the gut wall is very important in classification. The body cavity, which is lined by mesoderm is called coelom. Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates (Figure 4.3a). In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm. Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes (Figure 4.3b). The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes (Figure 4.3c).

Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals (platyhelminthes to chordates, Figure 4.2b).

Segmentation
In some animals, the body is externally and internally divided into segments with a serial repetition of at least some organs. For example, in earthworm, the body shows this pattern called metameric segmentation and the phenomenon is known as metamerism.
Notochord
Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, e.g., porifera to echinoderms.
Classification of animals
The broad classification of Animalia based on common fundamental features as mentioned in the preceding sections is given in Figure 4.4. The important characteristic features of the different phyla are described.

Phylum – Porifera
Members of this phylum are commonly known as sponges. They are generally marine and mostly asymmetrical animals (Figure 4.5). These are primitive multicellular animals and have cellular level of organisation. Sponges have a water transport or canal system. Water enters through minute pores (ostia) in the body wall into a central cavity, spongocoel, from where it goes out through the osculum. This pathway of water transport is helpful in food gathering, respiratory exchange and removal of waste. Choanocytes or collar cells line the spongocoel and the canals. Digestion is intracellular. The body is supported by a skeleton made up of spicules or spongin fibres. Sexes are not separate (hermaphrodite), i.e., eggs and sperms are produced by the same individual. Sponges reproduce asexually by fragmentation and sexually by formation of gametes. Fertilisation is internal and development is indirect having a larval stage which is morphologically distinct from the adult. Examples: Sycon (Scypha), Spongilla (Fresh water sponge) and Euspongia (Bath sponge).

Phylum – Coelenterata (Cnidaria)
They are aquatic, mostly marine, sessile or free-swimming, radially symmetrical animals (Figure 4.6). The name cnidaria is derived from the cnidoblasts or cnidocytes (which contain the stinging capsules or nematocysts) present on the tentacles and the body. Cnidoblasts are used for anchorage, defense and for the capture of prey (Figure 4.7). Cnidarians exhibit tissue level of organisation and are diploblastic. They have a central gastro-vascular cavity with a single opening, mouth on hypostome. Digestion is extracellular and intracellular. Some of the cnidarians, e.g., corals have a skeleton composed of calcium carbonate. Cnidarians exhibit two basic body forms called polyp and medusa (Figure 4.6). The former is a sessile and cylindrical form like Hydra, Adamsia, etc. whereas, the latter is umbrella-shaped and free-swimming like Aurelia or jelly fish. Those cnidarians which exist in both forms exhibit alternation of generation (Metagenesis), i.e., polyps produce medusae asexually and medusae form the polyps sexually (e.g., Obelia). Examples: Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan) and Meandrina (Brain coral).

Phylum – Ctenophora
Ctenophores, commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organisation. The body bears eight external rows of ciliated comb plates, which help in locomotion (Figure 4.8). Digestion is both extracellular and intracellular. Bioluminescence (the property of a living organism to emit light) is well-marked in ctenophores. Sexes are not separate. Reproduction takes place only by sexual means. Fertilisation is external with indirect development. Examples: Pleurobrachia and Ctenoplana.
Phylum – Platyhelminthes
They have dorso-ventrally flattened body, hence are called flatworms (Figure 4.9). These are mostly endoparasites found in animals including human beings. Flatworms are bilaterally symmetrical, triploblastic and acoelomate animals with organ level of organisation. Hooks and suckers are present in the parasitic forms. Some of them absorb nutrients from the host directly through their body surface. Specialised cells called flame cells help in osmoregulation and excretion. Sexes are not separate. Fertilisation is internal and development is through many larval stages. Some members like Planaria possess high regeneration capacity.
Examples: Taenia (Tapeworm), Fasciola (Liver fluke).

Phylum – Aschelminthes
The body of the aschelminthes is circular in cross-section, hence, the name roundworms (Figure 4.10). They may be freeliving, aquatic and terrestrial or parasitic in plants and animals. Roundworms have organ-system level of body organisation. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals. Alimentary canal is complete with a welldeveloped muscular pharynx. An excretory tube removes body wastes from the body cavity through the excretory pore. Sexes are separate (dioecious), i.e., males and females are distinct. Often females are longer than males. Fertilisation is internal and development may be direct (the young ones resemble the adult) or indirect. Examples : Ascaris (Round Worm), Wuchereria (Filaria worm), Ancylostoma (Hookworm).

Phylum – Annelida
They may be aquatic (marine and fresh water) or terrestrial; free-living, and sometimes parasitic. They exhibit organ-system level of body organisation and bilateral symmetry. They are triploblastic, metamerically segmented and coelomate animals. Their body surface is distinctly marked out into segments or metameres and, hence, the phylum name Annelida (Latin, annulus : little ring) (Figure 4.11). They possess longitudinal and circular muscles which help in locomotion. Aquatic annelids like Nereis possess lateral appendages, parapodia, which help in swimming. A closed circulatory system is present. Nephridia (sing. nephridium) help in osmoregulation and excretion. Neural system consists of paired ganglia (sing. ganglion) connected by lateral nerves to a double ventral nerve cord. Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious. Reproduction is sexual.
Examples : Nereis, Pheretima (Earthworm) and Hirudinaria (Blood sucking leech).

Phylum – Arthropoda
This is the largest phylum of Animalia which includes insects. Over two-thirds of all named species on earth are arthropods (Figure 4.12). They have organ-system level of organisation. They are bilaterally symmetrical, triploblastic, segmented and coelomate animals. The body of arthropods is covered by chitinous exoskeleton. The body consists of head, thorax and abdomen. They have jointed appendages (arthros-joint, poda-appendages). Respiratory organs are gills, book gills, book lungs or tracheal system. Circulatory system is of open type. Sensory organs like antennae, eyes (compound and simple), statocysts or balancing organs are present. Excretion takes place through malpighian tubules. They are mostly dioecious. Fertilisation is usually internal. They are mostly oviparous. Development may be direct or indirect. Examples: Economically important insects – Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect) Vectors – Anopheles, Culex and Aedes (Mosquitoes) Gregarious pest – Locusta (Locust) Living fossil – Limulus (King crab).

Phylum – Mollusca
This is the second largest animal phylum (Figure 4.13). Molluscs are terrestrial or aquatic (marine or fresh water) having an organ-system level of organisation. They are bilaterally symmetrical, triploblastic and coelomate animals. Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump. A soft and spongy layer of skin forms a mantle over the visceral hump. The space between the hump and the mantle is called the mantle cavity in which feather like gills are present. They have respiratory and excretory functions. The anterior head region has sensory tentacles. The mouth contains a file-like rasping organ for feeding, called radula. They are usually dioecious and oviparous with indirect development. Examples: Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish), Aplysia (Seahare), Dentalium (Tusk shell) and Chaetopleura (Chiton).

Phylum – Echinodermata These animals have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata (Spiny bodied, Figure 4.14). All are marine with organ-system level of organisation. The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical. They are triploblastic and coelomate animals. Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration. An excretory system is absent. Sexes are separate. Reproduction is sexual. Fertilisation is usually external. Development is indirect with free-swimming larva. Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).

Phylum – Hemichordata
Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata. Hemichordata have a rudimentary structure in the collar region called stomochord, a structure similar to notochord. This phylum consists of a small group of worm-like marine animals with organ-system level of organisation. They are bilaterally symmetrical, triploblastic and coelomate animals. The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk (Figure 4.15). Circulatory system is of open type. Respiration takes place through gills. Excretory organ is proboscis gland. Sexes are separate. Fertilisation is external. Development is indirect. Examples: Balanoglossus and Saccoglossus.

Phylum – Chordata
Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits (Figure 4.16). These are bilaterally symmetrical, triploblastic, coelomate with organ-system level of organisation. They possess a post anal tail and a closed circulatory system. Table 4.1 presents a comparison of salient features of chordates and non-chordates.

Comparison of Chordates and Non-chordates S.No. Chordates Non-chordates 1. Notochord present. Notochord absent. 2. Central nervous system is dorsal, Central nervous system is ventral, solid hollow and single. and double. 3. Pharynx perforated by gill slits. Gill slits are absent. 4. Heart is ventral. Heart is dorsal (if present). 5. A post-anal part (tail) is present. Post-anal tail is absent. Phylum Chordata is divided into three

subphyla: Urochordata or Tunicata, Cephalochordata and Vertebrata.
Subphyla Urochordata and Cephalochordata are often referred to as protochordates (Figure 4.17) and are exclusively marine.
In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life. Examples: Urochordata – Ascidia, Salpa, Doliolum; Cephalochordata – Branchiostoma (Amphioxus or Lancelet).
The members of subphylum Vertebrata possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult. Thus all vertebrates are chordates but all chordates are not vertebrates. Besides the basic chordate characters, vertebrates have a ventral muscular heart with two, three or four chambers, kidneys for excretion and osmoregulation and paired appendages which may be fins or limbs. Class – Cyclostomata All living members of the class Cyclostomata are ectoparasites on some fishes. They have an elongated body bearing 6-15 pairs of gill slits for respiration. Cyclostomes have a sucking and circular mouth without jaws (Fig. 4.18). Their body is devoid of scales and paired fins. Cranium and vertebral column are cartilaginous. Circulation is of closed type. Cyclostomes are marine but migrate for spawning to fresh water. After spawning, within a few days, they die. Their larvae, after metamorphosis, return to the ocean. Examples: Petromyzon (Lamprey) and Myxine (Hagfish).

Class – Chondrichthyes
They are marine animals with streamlined body and have cartilaginous endoskeleton (Figure 4.19). Mouth is located ventrally. Notochord is persistent throughout life. Gill slits are separate and without operculum (gill cover). The skin is tough, containing minute placoid scales. Teeth are modified placoid scales which are backwardly directed. Their jaws are very powerful. These animals are predaceous. Due to the absence of air bladder, they have to swim constantly to avoid sinking. Heart is two-chambered (one auricle and one ventricle).
Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e.g., Trygon). They are cold-blooded (poikilothermous) animals, i.e., they lack the capacity to regulate their body temperature. Sexes are separate. In males pelvic fins bear claspers. They have internal fertilisation and many of them are viviparous.
Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray).

Class – Osteichthyes
It includes both marine and fresh water fishes with bony endoskeleton. Their body is streamlined. Mouth is mostly terminal (Figure 4.20). They have four pairs of gills which are covered by an operculum on each side. Skin is covered with cycloid/ctenoid scales. Air bladder is present which regulates buoyancy. Heart is twochambered (one auricle and one ventricle). They are cold-blooded animals. Sexes are separate. Fertilisation is usually external. They are mostly oviparous and development is direct. Examples: Marine – Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater – Labeo (Rohu), Catla (Katla), Clarias (Magur); Aquarium – Betta (Fighting fish), Pterophyllum (Angel fish).

Class – Amphibia
As the name indicates (Gr., Amphi : dual, bios, life), amphibians can live in aquatic as well as terrestrial habitats (Figure 4.21). Most of them have two pairs of limbs. Body is divisible into head and trunk. Tail may be present in some. The amphibian skin is moist (without scales). The eyes have eyelids. A tympanum represents the ear. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior. Respiration is by gills, lungs and through skin. The heart is threechambered (two auricles and one ventricle). These are cold-blooded animals. Sexes are separate. Fertilisation is external. They are oviparous and development is indirect. Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia).

Class – Reptilia
The class name refers to their creeping or crawling mode of locomotion (Latin, repere or reptum, to creep or crawl). They are mostly terrestrial animals and their body is covered by dry and cornified skin, epidermal scales or scutes (Fig. 4.22). They do not have external ear openings. Tympanum represents ear. Limbs, when present, are two pairs. Heart is usually three-chambered, but four-chambered in crocodiles. Reptiles are poikilotherms. Snakes and lizards shed their scales as skin cast. Sexes are separate. Fertilisation is internal. They are oviparous and development is direct. Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator). Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).

Class – Aves
The characteristic features of Aves (birds) are the presence of feathers and most of them can fly except flightless birds (e.g., Ostrich). They possess beak (Figure 4.23). The forelimbs are modified into wings. The hind limbs generally have scales and are modified for walking, swimming or clasping the tree branches. Skin is dry without glands except the oil gland at the base of the tail. Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic). The digestive tract of birds has additional chambers, the crop and gizzard. Heart is completely fourchambered. They are warm-blooded (homoiothermous) animals, i.e., they are able to maintain a constant body temperature. Respiration is by lungs. Air sacs connected to lungs supplement respiration. Sexes are separate. Fertilisation is internal. They are oviparous and development is direct. Examples : Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture).

Class – Mammalia
They are found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands and dark caves. Some of them have adapted to fly or live in water. The most unique mammalian characteristic is the presence of milk producing glands (mammary glands) by which the young ones are nourished. They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying (Figure 4.24). The skin of mammals is unique in possessing hair. External ears or pinnae are present. Different types of teeth are present in the jaw. Heart is fourchambered. They are homoiothermous. Respiration is by lungs. Sexes are separate and fertilisation is internal. They are viviparous with few exceptions and development is direct. Examples: Oviparous-Ornithorhynchus (Platypus); Viviparous - Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion). The salient distinguishing features of all phyla under animal kingdom is comprehensively given in the Table 4.2

1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?
2. If you are given a specimen, what are the steps that you would follow to classify it?
3. How useful is the study of the nature of body cavity and coelom in the classification of animals?

4. Distinguish between intracellular and extracellular digestion?
5. What is the difference between direct and indirect development?
6. What are the peculiar features that you find in parasitic platyhelminthes?
7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?
8. Water vascular system is the characteristic of which group of the following: (a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata
9. “All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement.
10. How important is the presence of air bladder in Pisces?
11. What are the modifications that are observed in birds that help them fly?
12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?

13. Segmentation in the body is first observed in which of the following:
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda
14. Match the following:
(a) Operculum (i) Ctenophora
(b) Parapodia (ii) Mollusca
(c) Scales (iii) Porifera
(d) Comb plates (iv) Reptilia
(e) Radula (v) Annelida
(f ) Hairs (vi) Cyclostomata and Chondrichthyes
(g) Choanocytes (vii) Mammalia
(h) Gill slits (viii) Osteichthyes
15. Prepare a list of some animals that are found parasitic on human beings.
Assignment 1-10

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Classification in Nutshell - Phyla

Porifera, Coelenteratrata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata and Chordata

Phylum Chordata - Hemichordata, Protochordata, Cephalochordata and vertebrata

Now Hemichordata also discussed as phylum and also sometimes under Invertebrates.

Interphylum (or sub phylum) Agnatha (Class Cyclostomata)

Sub-phylum Gnathostomata - two super classes Pisces and Tetrapoda

super class Pisces includes classes Chondrichthyes, Osteichthyes and Placodermi,

super class Tetrapoda includes Classes Amphibia, Reptilia, Aves and Mammalia

Groupwise classification

Porifera-Based on the spicules which are made up of calcium carbonate, sponges can be classified into three classes.

Calcarea, Hexactinellida and Demospongiae

Coelenterata- Anthozoa, Hydrozoa and Scyphozoa

Ctenophora has two classes - tenticulata (ctenophores with tentacles) and nuda

Platyhelminthes - Turbellaria,Trematoda and Cestoda

Annelida - Polychaeta, Oligochaetaa, Hirudinea and Archiannelida

Arthropoda- Crustacea, Chelicerata, Myriapoda, and Hexapoda
However, two other classes of arthropods can also be derived ─ Trilobitomorpha, the extinct category and Onychophora.

The Crustacea can be Further Divided into Six Sub-Categories- - Remipedia, Branchiopoda, Maxillopoda, Cephalocarida, Malacostraca and Ostracoda

Chelicerata- has Three Sub Categories namely Pycnogonida, Merostomata and Arachnida.

Myriapoda is Classified into Four Sub Categories- Chilopoda, Symphyla, Pauropoda and Diplopoda

Hexapoda has two Classes

Entognatha and Insecta

Onychophora has one class only Udeonychophora.

Trilobitomorpha has only a single class Trilobita.

Classification of Mollusca - Aplacophora or Solenogasters, Monoplacophora, Polyplacophora, Gastropoda, Scaphopoda, Pelecypoda and Cephalopoda

Classification of Echinodermata-Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea, Crinoidea

Hemichordata have Classes Enteropneusta, Pterobranchia: and Planctosphaeroidea.

Phylum Chordata is classified into three subphyla, namely Urochordata (tunicates), Cephalochordata (lancelets) and Vertebrata (vertebrates).

Urochordates are subdivided into three classes - Ascidiacea, Thaliacea, and Larvacea.

The subphylum Cephalochordata comprises a single family Brachiostomatidae with two genera Branchiostoma (Costa, 1834) and Asymmetron (Andrews, 1893).

Classification of Vertebrates - 7 classes based on their anatomical and physiological features. Jawless fishes (Class Agnatha*), Cartilaginous fishes (Class Chondrichthyes), Bony fishes (Class Osteichthyes), Amphibians (Class Amphibia), Reptiles (Class Reptilia), Birds (Class Aves) and Mammals (Class Mammalia).
Class Agnatha ( included as sub phylum by many authors has one class Cyclostomata.

Class Chondrichthyes is subdivided into two subclasses -Elasmobranchii and Holocephali

Osteichthyes is subdivided into two subclasses - Sarcopterygii and Actinopterygii

The Amphibians are divided into three orders - Apoda (Gymnophiona or Caecilia), Urodela (Caudata) and Anura (Salientia). * Also referred as anamniotes. ** Reptilia, Aves and Mammals are amniotes.

The class Reptilia is differentiated into three major sub-classes-Anapsida, Parapsida and Diapsida

Classification of Aves - two categories namely Archaeornithes and Neornithes
The neornithine birds are arranged in four superorders—Odontognathae, Palaeognathae, Impennae and Neognathae

Classification of Mammalia -
Subclass I prototheria include Order 1. Monotremata (Duckbilled platypus, Echidna) (b) Sub class II. Theria is divided into two infraclasses namely Metatheria and Eutheria.

Infraclass 1. Metatheria has

order1 ………… and Order 2. Marsupialia.
Order Notoryctemorphia (Marsupial modes)
Diprotodontia (Kangaroo)
Microbiotheria (Colocolo)
Didelphimorphia (New world opossum)
Dasyuromorphia (Dasyurids)
Peramelemorphia (Bandicoots)
Paucituberculata (South American rat opossum)

Infraclass 2. Eutheria consists of 19 orders. A few are given , - Insectivora, Chiroptera, Edentata , Pholidota, Rodentia , Lagomorpha, Carnivora, Cetacea , Tubulidentata, Proboscidea , Hyracoidea, Perissodactyla, Artiodactyla and Primates

Classification Animalia - Preface
Phylum Porifera
Phylum Coelenteratrata
Phylum Platyhelminthes
Phylum Aschelminthes
phylum Annelida
Phylum Arthropoda
Phylum mollusca
phylum Echinodermata
Chordata includes the following
Hemichordata, Protochordata, Cephalochordata and vertebrata
Now Hemichordata are discussed as sub phylum under Phylum Chordata
Hemichordata, Protochordata, Cephalochordata
Phylum vertebrata
Class Chondrichthyes
Class Osteichthyes
Class Amphibia
Class Reptilia
Class Aves
Class Mammalia

NCERT Pg 46 Classification Animalia Preface As over a million species of animals have been described till now, the need for classification becomes all the more important. The classification also helps in assigning a systematic position to newly described species.

Basis of classification
00

Inspite of differences in structure and form of different animals, there are fundamental features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems. These features are used as the basis of animal classification and some of them are discussed here.

Levels of Organisation

Though all members of Animalia are multicellular, all of them do not exhibit the same pattern of organisation of cells. For example, in sponges, the cells are arranged as loose cell aggregates, i.e., they exhibit cellular level of organisation. Some division of labour (activities) occur among the cells.

In coelenterates, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues, hence is called tissue level of organisation. A still higher level of organisation, i.e., organ level is exhibited by members of Platyhelminthes and other higher phyla where tissues are grouped together to form organs, each specialised for a particular function.

In animals like Annelids, Arthropods, Molluscs Echinoderms and Chordates, organs have associated to form functional systems, each system concerned with a specific physiological function.

This pattern is called organ system level of organisation. Organ systems in different groups of animals exhibit various patterns of complexities.

For example, the digestive system in Platyhelminthes has only a single opening to the outside of the body that serves as both mouth and anus, and is hence called incomplete.

Level of Organisation

It is of five types -
acellular, cellular,
tissue,
organ and
organ system.
1. Acellular or Protoplasmic Level. It is found in protists where the body consists of mass of protoplasm.
2. Cellular Level. The body consists of a number of cells. Cellular colony level of organisation is found in protists and some algae (e.g., Volvox) while cellular aggregate level of organisation is found in sponges where the cells are not organised into tissues.
3. Tissue Level (cell Tissue Level). The multicellular body shows organisation into tissues but not of the higher level, e.g., ectoderm and endoderm in coelenterates.
4. Organ Level (Tissue Organ Level). The multicellular body has tissues which are arranged to form organs, e.g., flatworms.
5. Organ System Level. The multicellular body shows organisation into tissues, tissues into organs and organs into organ-systems, e.g., Roundworms, Annelids, Molluscs, Arthropods, Echinoderms, Chordates. A digestive tract is present in all those animals which show tissue and higher levels of organisation. They are collectively called enterozoa (also for intestinal parasites).

Body Plan

1. Cell Aggregate Body Plan. There is little differentiation of cells, e.g., sponges.
2. Blind Sac Plan (Hollow Sac Plan). The body has a cavity or is like a sac with one opening that functions as mouth and anus. Digestive tract is, therefore. incomplete. Cells are organised into tissues, e.g., coelenterates, flatworms.
3. Tube-within a Tube Plan. Body wall forms an outer tube while digestive tract forms an internal tube. It has two openings, mouth and anus, so that digestive tract is complete. In prostomic forms mouth is formed from blastopore region and appears first in the embryo (e.g., roundworms, annelids, arthropods, molluscs) while in deuterostomic forms anus develops from blaslopore region and appears first in the embryo (e.g., echinoderms, chordates).

A complete digestive system has two openings, mouth and anus. Similarly, the circulatory system may be of two types:

(i) open type in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it and

(ii) closed type in which the blood is circulated through a series of vessels of varying diameters (arteries, veins and capillaries).

Symmetry

Animals can be categorised on the basis of their symmetry.
1. Asymmetrical. Body cannot be divided into equal halves by any plane of division, e.g., some sponges.
2. Spherical Symmetry. The body is like a sphere and it can be divided into two equal parts by any plane of division, e.g., some corals.
3. Radial Symmetry. The body is cylindrical or discoid with similar parts radiating on all sides so that it is divisible into two halves by vertical plane passing through central axis, e.g., many sponges, coelenterates and echinoderms. It is more common in sedentary forms. In Sea Anemones the body has biradial symmetry (symmetrical both radially and bilaterally).
4. Bilateral Symmetry. All important organs and limbs are paired and arranged on two sides of a central axis so that the body is divisible into two halves by one plane only mid-sagittal. The body has a dorsal (upper, vertebral) side, a ventral side, two lateral sides, anterior (head part), posterior, proximal (basal or near site of origin) and distal (head/mouth region or away from site of origin) parts. Bilateral symmetry developed due to ceIphalization.

Cephalization and Appendages

Differentiation of head in the anterior region is called cephalization. It evolved in the remote past due to creeping habit where the anterior end encountered obstacles and food so that major sense organs, nervous tissue and food catching regions became concentrated here in the form of head. Appendages are projecting parts of the body which are used for specific functions like feeding locomotion and sensation, e.g., tentacles, setae, parapodia, antennae, legs, wings, fins, etc.

Metameric Segmentation

Body structure having repeated segments (= metameres = so mites) is called segmentation or metamerism. Segments or metameres help develop specialization. External segmentation corresponds to internal segmentation in annelids. This is popularly called metameric segmentation. In arthropods both external and internal segmentation occur but due to undivided coelom the two do not correspond. In chordates only internal segmentation is present. The same is apparent in emrbyo. In adult, it is found in the arrangement of muscles, nerves, blood vessels, vertebrae, etc. False segmentation (pseudometamerism = pseudosegmentation) occurs through budding in tapeworms.

Reproduction and Development

Most animals multiply by sexual means. For this they develop sex organs. Meiosis occurs during the formation of gametes (gametic meiosis). Male gametes are generally motile. They are called spermatozoa. Female gametes are nonmotile. They are termed as ova. Fusion of the two types of gametes is called fertilization. It produces a diploid zygote. The zygote undergoes cleavage and other types of divisions followed by differentiation and development to form the complete organism as offspring.

Germinal Layers

Germinal or germ layers are primary layers. which differentiate at the time of gastrulation in a developing embryo. All the tissues and organs develop from the germinal layers. There are maximum three germinal layers-ectoderm (outer), mesoderm (middle) and endoderm (inner). Animals having two germinal layers (ectoderm and endoderm) are called diploblastic, e.g., porifers, coelenterates. Animals with three germinal layer (ectoderm, mesoderm and endoderm) and triploblastic, viz., platyhelminthes to chordates.

Diploblastic and Triploblastic Organisation

Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g., coelenterates. An undifferentiated layer, mesoglea, is present in between the ectoderm and the endoderm (Figure 4.2a).

Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals (platyhelminthes to chordates, Figure 4.2b).

Coelom

Presence or absence of a cavity between the body wall and the gut wall is very important in classification.
The body cavity, which is lined by mesoderm is called coelom.

Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods, echinoderms, hemichordates and chordates.
In some animals, the body cavity is not lined by mesoderm, instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm.
Such a body cavity is called pseudocoelom and the animals possessing them are called pseudocoelomates, e.g., aschelminthes Figure.
The animals in which the body cavity is absent are called acoelomates, e.g., platyhelminthes.

Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals (platyhelminthes to chordates, Fig. Coelom.
Coelom is the name of internal or body cavity which is filled with a fluid and is lined by peritoneum derived from mesoderm. It is either formed by splitting a mesoderm (schizocoelom, e.g., annelids, molluscs, arthropods) or as outgrowth of embryonic gut (enterocoel om, e.g., echinoderms, chordates'. Animals which do not have a body cavity are called acoelomates (e.g., porifers, coelenterates, flatworms).
Some animals possess a false body cavity or pseudocoelom that develops from blastocoel and is not lined by peritoneum, e.g., roundworms.
Animals having true codom are called coelomates or eucoelomates. In arthropods and molluscs, the actual or true coelom is reduced but spaces between viscera grow and form a large cavity filled with blood. It is called haemocoel (= haemocoelom).

Protostomes and Deuterostomes

Protostomes are true coelomates which have spiral cleavage of egg with blastospore forming mouth (or mouth and anus). A trochophore larva is generally present. Deuterostomes (Gk. deuteros-second, stoma - mouth) are true coelomates with radial cleavage of egg and blastopore forming the anus. Enterocoel occurs. Mouth is formed secondarily as distinct from gastrula mouth (larva is generally dipleurula).

Segmentation

In some animals, the body is externally and internally divided into segments with a serial repetition of at least some organs.

For example, in earthworm, the body shows this pattern called metameric segmentation and the phenomenon is known as metamerism.

Notochord

Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and those animals which do not form this structure are called non-chordates, e.g., porifera to echinoderms.
Nutrition
There are two types of nutrition - autotrophic (manufacture of organic food from raw materials) and heterotrophic (obtaining organic food from outside). Animals are heterotrophs with the exception of some protozoans. They have three types of feeding habits - ingestive (holozoic), saprobic and parasitic. Ingestive nutrition is typical animal mode of nutrition. It has several types - herbivorous (feeding on plants), carnivorous (preying over other animals), omnivorous (eating both animals and plants), detrivorous (feeding on detritus), scavenging (eating carrions), frugivorous (eating fruits), insectivorous (eating insects), cannibalism (eating other members of own species), sanguivorous (taking meal of blood), coprophagous (eating one's own faeces), coprozoic (feeding on dung), etc.

Active Movement

Compared to members of other kingdoms, animals show active movements which involve shifting from place to place or locomotion. It is due to flexibility of their cells, presence of muscular tissue and body joints. A number of- locomotion modes are known, e.g., flight, climbing, swimming, walking, running, gliding, looping, crawling, etc. Some animals are, however, fixed, e.g., porifers, corals.

Metamorphosis

Metamorphosis (Gk. meta-between, morphe-form) is the change of form and structure that occurs during transition fromJarval to adult stage. It is found in many invertebrates, protochordates, some fishes and amphibians. Different types of larvae occur in different groups (table 3.7.1). They take part in (i) Dispersal (ii) Exploit a "more congenial ecological niche. (iii) Transition for adaptation to adult habitats. For example, tadpole produces 80% ammonia as nitrogenous waste while during metamorphosis it is 80% urea. (iv) Allow dormancy in adverse conditions, e.g., pupa. (v) Allow multiplication e.g., platyhelminthes. (vi) Undertake sexual reproduction in certain cases, e.g., axolotl. Metamorphosis is controlled by endocrine secretions or hormones. In insects brain produces prothoracitrophic hormone (PTTH) from its neurosecretory cells. It acts on corpus allatum to induce synthesis of juvenile hormone or neutenin. PTTH also acts on prothoracic glands for synthesis of ecdysone or moulting hormone (Wigglesworth) required for moulting. Juvenile hormone interacts with ecdysone and keeps the cuticle soft. Towards the end of larval stage, secretion of juvenile hormone stops and hard adult cuticle develops. Ecdysone producing glands degenerate and moulting stops thereafter. Adult organs develop during pupal stage.
In amphibians change in external environment activates hypothalamus to secrete thyrotrophin releasing hormone (TRH). It stimulates pituitary to produce thyroid stimulating hormone (TSH) or thyrotrophin. The latter acts on thyroid which secretes hormone thyroxine. Thyroxine acts on different tadpole tissues giving rise to varying responses like atrophy of tail and gills, growth of limbs and tongue, skin pigmentation, etc. In axolotl, the pituitary gland does not produce TSH even through the larva may come to have sexual maturity or neoteny.
Skeleton
It is a hard internal or external framework that supports the body Skeleton is of two types, endoskeleton and exoskeleton. Exoskeleton is secreted by skin or ectoderm and is usually made of non-living materials, e.g., calcareous shell of molluscs, chitinous cuticle of arthropods, plates below skin in echinoderms, hair, nails, claws, hoofs, horns, feathers, scales, etc. Endoskeleton is internal skeleton which is produced by mesoderm or occasionally endoderm. It may be living (e.g., cartilage and bone in vertebrates) or non-living (e.g., spicules in sponges).

Classification ( A sketch)

Porifera

Based on the spicules which are made up of calcium carbonate, sponges can be classified into three classes.

Calcarea, Hexactinellida and Demospongiae

Coelenterata

Anthozoa, Hydrozoa and Scyphozoa

Ctenophora has two classes

tenticulata (ctenophores with tentacles) and nuda

Platyhelminthes

Turbellaria,Trematoda and Cestoda

Annelida

Polychaeta, Oligochaetaa, Hirudinea and Archiannelida

Arthropoda

Crustacea, Chelicerata, Myriapoda, and Hexapoda. However, two other classes of arthropods can also be derived ─ Trilobitomorpha, the extinct category and Onychophora.

The Crustacea can be Further Divided into Six Sub-Categories-

Remipedia, Branchiopoda, Maxillopoda, Cephalocarida, Malacostraca and Ostracoda

Chelicerata

has Three Sub Categories ─ Pycnogonida, Merostomata and Arachnida.

Myriapoda is Classified into Four Sub Categories─ Chilopoda, Symphyla, Pauropoda and Diplopoda

Hexapoda has two Classes

Entognatha and Insecta

Onychophora

has one class only Udeonychophora.

Trilobitomorpha

had only a single class Trilobita.

Classification of Mollusca

Aplacophora or Solenogasters, Monoplacophora, Polyplacophora, Gastropoda, Scaphopoda, Pelecypoda and Cephalopoda

Classification of Echinodermata

Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea, Crinoidea

Hemichordata have Classes Enteropneusta, Pterobranchia: and Planctosphaeroidea.

Phylum Chordata is classified into three subphyla, namely Urochordata (tunicates), Cephalochordata (lancelets) and Vertebrata (vertebrates).

Urochordates are subdivided into three classes

Ascidiacea, Thaliacea, and Larvacea.

The subphylum Cephalochordata comprises a single family Brachiostomatidae with two genera Branchiostoma (Costa, 1834) and Asymmetron (Andrews, 1893).

Classification of Vertebrates

7 classes based on their anatomical and physiological features. Jawless fishes (Class Agnatha), Cartilaginous fishes (Class Chondrichthyes), Bony fishes (Class Osteichthyes), Amphibians (Class Amphibia), Reptiles (Class Reptilia), Birds (Class Aves) and Mammals (Class Mammalia).

Class Chondrichthyes is subdivided into two subclasses

Elasmobranchii and Holocephali

Osteichthyes is subdivided into two subclasses:

Sarcopterygii and Actinopterygii

The Amphibians are divided into three orders

Apoda (Gymnophiona or Caecilia), Urodela (Caudata) and Anura (Salientia).

The class Reptilia is differentiated into three major sub-classes:

Anapsida, Parapsida and Diapsida

Classification of Aves

two categories namely Archaeornithes and Neornithes The neornithine birds are arranged in four superorders—Odontognathae, Palaeognathae, Impennae and Neognathae:

Classification of Mammalia Subclass I prototheria include Order 1. Monotremata and (b) Sub class II. Theria is divided into two infraclasses namely Metatheria and Eutheria.

Infraclass 1. Metatheria has

order1 ………… and Order 2. Marsupialia .

Infraclass 2. Eutheria

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Notes  Aquatic Animals Aquatic animals may be fresh water or marine. The animals living in open water or sea are called pelagic. They are of two types, plankton (= zooplankton, drifting with water currents, e.g., invertebrate larvae, small invertebrates) and nekton (= necton, actively swimming even against water flow, e.g., fishes). The animals living at the bottom are called benthon (e.g., Star Fish). Other terms are: Neuston - floating or swimming in surface water. Seston -living or nonliving, floating or swimming in water. Tripton-nonliving seston. Neritic -in coastal waters. Sedentary (Sessile)-animals fixed to substratum. Sedentary animals can be epizoons (over other animals), periphytons (attached over rooted plants) or epiphytic, epilithic (on rocks, stones), etc. Benthon may be sedentary or motile. Terrestrial Animals They live on land. Fossorial-in burrows, e.g., Rabbit. Animals resting in burrows are subterrestrial. Arboreal- on trees, e.g., Monkey. Scansorial- adapted to climbing, e.g., Wall Lizard. Cursorial-Running, e.g., Horse. Flying/Aerial- Winged, e.g., bird. Cave Dwelling. Living in caves. Nocturnal. Coming out or active during night. Diurnal. Coming out or active during day time. Crepuscular. Coming out in twilight. Vespertine. Coming out during evening. Auroral. Coming out at dawn. CLASSIFICATION OF ANIMALS

Phylum ─ Porifera

Phylum ─ Coelenterata (Cnidaria)

Phylum ─ Ctenophora

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Phylum ─Platyhelminthes

5. Some of them absorb nutrients from the host directly through their body surface. 6. Specialised cells called flame cells help in osmoregulation and excretion. 7. Sexes are not separate. 8. Fertilisation is internal and development is through many larval stages. 9. Some members like Planaria possess high regeneration capacity.
Examples: Taenia (Tapeworm), Fasciola (Liver fluke).

Phylum ─ Aschelminthes

Phylum ─ Annelida

1. They may be aquatic (marine and fresh water) or terrestrial; free-living, and sometimes parasitic.
2. They exhibit organ-system level of body organisation and bilateral symmetry.
3. They are triploblastic, metamerically segmented and coelomate animals.
4. Their body surface is distinctly marked out into segments or metameres and, hence, the phylum name Annelida (Latin, annulus : little ring) Fig.
5. They possess longitudinal and circular muscles which help in locomotion. Aquatic annelids like Nereis possess lateral appendages, parapodia, which help in swimming.
6. A closed circulatory system is present. Nephridia (sing. nephridium) help in osmoregulation and excretion.
7. Neural system consists of paired ganglia (sing. ganglion) connected by lateral nerves to a double ventral nerve cord. 8. Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious.
9. Reproduction is sexual. 9. Examples : Nereis, Pheretima (Earthworm) and Hirudinaria (Blood sucking leech).

Phylum ─Arthropoda

This is the largest phylum of Animalia which includes insects.
Over two-thirds of all named species on earth are arthropods Fig.
They have organ-system level of organisation. They are bilaterally symmetrical, triploblastic, segmented and coelomate animals.
1. The body of arthropods is covered by chitinous exoskeleton. The body consists of head, thorax and abdomen.
2. They have jointed appendages (arthros-joint, poda-appendages).
3. Respiratory organs are gills, book gills, book lungs or tracheal system.
4. Circulatory system is of open type. Sensory organs like antennae, eyes (compound and simple), statocysts or balancing org ans are present. Excretion takes place through malpighian tubules.
5. They are mostly dioecious. Fertilisation is usually internal. They are mostly oviparous. Development may be direct or indirect.
6. Examples: Economically important insects
─Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect) Vectors ─ Anopheles, Culex and Aedes (Mosquitoes)

Gregarious pest ─ Locusta (Locust)

Living fossil ─Limulus (King crab).

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Arthropoda (with type studies) Phylum ─ Mollusca
1. This is the second largest animal phylum (Fig.) Molluscs are terrestrial or aquatic (marine or fresh water) having an organ-system level of organisation.

2. They are bilaterally symmetrical, triploblastic and coelomate animals.

3. Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump.
4. A soft and spongy layer of skin forms a mantle over the visceral hump. The space between the hump and the mantle is called the mantle cavity in which feather like gills are present.
5. They have respiratory and excretory functions. The anterior head region has sensory tentacles.
6. The mouth contains a file-like rasping organ for feeding, called radula.
7. They are usually dioecious and oviparous with indirect development.
Examples: Pila (Apple snail),
Pinctada (Pearl oyster)
, Sepia (Cuttlefish)
, Loligo, Octopus (Devil fish), Aplysia (Sea- hare), Dentalium (Tusk shell) and Chaetopleura (Chiton)
.

Phylum ─ Echinodermata
1. These animals have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata (Spiny bodied, Figure).
2. All are marine with organ-system level of organisation.
3. The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
4. They are triploblastic and coelomate animals.
5. Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side.
6. The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration.
7. An excretory system is absent.
8. Sexes are separate.
9. Reproduction is sexual. Fertilisation is usually external. Development is indirect with free-swimming larva.
Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star). → The main function of Tiedemann's bodies is to produce amoebocytes. - Towards the outer side of the ring canal large vesicular structures are present on each arm known as Polian vesicles. The main function of Polian vesicles is to store additional amounts of water.
Madreporite or sieve plate: a small, smooth plate, at the entrance of the sea star's water vascular system, through which the sea star takes in sea water. It's located on the aboral side of the sea star, slightly off the center. ↔

Sub Phylum ─ Hemichordata
1. Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata.
2.Hemichordata have a rudimentary structure in the collar region called stomochord, a structure similar to notochord.
→ The stomochord arises as an outgrowth from the outer cells of the embryonic gut whereas notochord is developed from cells from the mesoderm, which is a middle layer of the embryo. Hence, the notochord is not an outgrowth, as it is developed from the dorsal cells inside the embryonic gut. Stomocord helps in locomotion while notochord is supportive in function. ↔ 3. This phylum consists of a small group of worm-like marine animals with organ-system level of organisation.
4.They are bilaterally symmetrical, triploblastic and coelomate animals.
5.The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk (Figure).
6. Circulatory system is of open type.
7. Respiration takes place through gills.
8.Excretory organ is proboscis gland.
9. Sexes are separate. Fertilisation is external. Development is indirect. Examples: Balanoglossus and Saccoglossus.

Phylum─ Chordata

1. Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits (Figure).

2. These are bilaterally symmetrical, triploblastic, coelomate with organ-system level of organisation.

3. They possess a post anal tail and a closed circulatory system.

Comparison of Chordates and Non-chordates

Diagnostic Features of Chordates

Chordates evolved during ordovician. They possess three diagnostic features - notochord, dorsal hollow nervous system and pharyngeal gill slits. Number of species is about 50,000.
1. Notochord (Chorda Dorsalis). It' is an elastic, solid, ensheathed rod like structure of vacuolated turgid cells which develops between dorsal hollow nervous system and alimentary canal (from dorsal part of gut wall). Animals without notochord are called non-chordates. Muscles for body movement are attached to it. In vertebrates, notochord is replaced by cranium and vertebral column.
2. Dorsal Hollow Nervous System. It is present mid-dorsally above the notochord. It may differentiated into brain and spinal cord. In nonchordates the central nervous system is generally ventral, solid and double.
3. Pharyngeal Gill Slits. They are paired perforations found on the lateral sides of pharynx. In lower chordates they take part in circulation of water for respiration. In higher chordates they occur only in the embryo stage. Gill slits are absent in nonchordates.
4. Tail. Tail is metamerically segmented post-anal part of the body meant for balancing. In nonchordates tail or pygidium is terminal but nonsegmented.
5. Epidermis. Epidermis (of skin) consists of stratified epithelium. It is made of a single layer of cells in nonchordates. Below epidermis is present a dermis made of mesodermal connective tissue.
6. Cephalisation. It is well developed. A brain has evolved in the region of head.
7. Segmentation. It occurs in embryo which shows development of somites. Arrangement of muscles, nerves, vertebrae and blood vessels also indicates internal segmentation.
8. Endocrine System. It has developed to promote coordination of body parts and their functions, growth and development.
9. Appendages. Most of the chordates possess two pairs of appendages, one pair at the beginning of the trunk and other pair at the posterior end of the trunk.
10. Coelom. A true coelom (enterocoelom) is present which is lined externally by the parietal peritoneum and internally by the visceral peritoneum. In most of the chordates it is divided into pericardial cavity around the heart, pleural sacs around the lungs and abdominal cavity in the abdomen.
11. Vascular System. It is closed. Blood is red due to the presence of haemoglobin in the cytoplasm of RBCs. The blood of some non-chordates may also be red, but RBCs in them are absent and haemoglobin is dissolved in the plasma.
12. Heart. In most chordates a pumping heart is present on the ventral side, whereas heart in non-chordates if present is either dorsal or lateral in position.
13. Kidney. Most of the chordates, possess one pair of kidneys for excretion. True kidneys are absent in nonchordates.
14. Endoskeleton. A living endoskeleton of bones and cartilages is present. It is absent in non-chordates.
15. Organisation. Chordates are triploblastic, bilaterally symmetrical animals with organ-system level of organisation and tube within-a-tube body plan.
16. Reproduction. Most of the animals are unisexual. There is present one pair of gonads. The mode of reproduction is sexual only.

Classification

Phylum chordata is divisible into four subphyla - hemichordata, urochordata, cephalochordata and vertebrata. The first three subphyla are marine non-vertebrate chordates. They have been placed in a separate group protochordata. Proto chordates are characterised by the absence of paired appendages, absence of vertebral column, absence of jaws, absence of cranium and absence of brain. Due to absence of cranium, the group protochordata is also called acraniata. Another term is prevertebrata.

Subphylum Hemichordata or Stomochordata (Gk. hemi - half, chordata with notochor.)

(i) The animals possess dorso-ventral pharyngeal gill slits for respiration.
(ii) Tubular dorsal nerve cord is present but restricted to collar region.
(iii) True notochord is absent but a preoral buccal diverticulum called stomochord (a hollow outgrowth of gut) is present. It is considered to be primitive notochord though it does not have any supporting or anchoring function. Covering sheaths are absent. It has no relation with blastopore.
(iv) Tail is absent. Body is divisible into pre-oral proboscis, a small collar and a long trunk. (v) Body wall has single layered epidermis.
(vi) Excretory system consists of proboscis gland called glomerulus.
(vii) Heart is present but dorsal. Dorsal and ventral blood vessels are present which are connected by lateral vessels and sinuses.
(vii) Circulatory system is open. A respiratory pigment is absent.
(ix) Development may include larva called tornaria.
Example. Balanoglossus, Saccoglossus, Cephalodiscus, Glossobalanus.
Because of the absence of true notochord, hemichordata has been taken out of chordata and placed in a separate phylum of its own. Balanoglossus (Tongue/Acorn Worm) It is a saprozoic hemichordate which lives in shallow coastal waters inside V-shaped burrows. The body is cylindrical, worm-like and ciliated for most part. It is divisible into proboscis, collar and trunk. Mouth is present in collar behind the stalk of proboscis. Locomotion is with the help of cilia and body contractions. Food is obtained from swallowed mud. It consists of organic matter and microorganisms. Power of regeneration is high.
Subpbylum Urochordata or Tunichordata (Gk. Ufo - tail, chordata - with notochord)
(i) Adults undergo retrogressive metamorphosis. Chordate characters usually occur in the larva (tadpole) which is therefore, more complex.
(ii) The adult is covered by a tunic or test of cellulose-like organic substance called tunicin. Because of it, urochordata is also called tunicata.,
(iii) Notochord occurs only in the tail region of the larva.
(iv) A dorsal tubular nerve cord occurs in the larva. It is changed to a single dorsal ganglion in adult.
(v) Gill slits occur both in larva and adult. In adult, they open into an atrium or cavity.
(vi) Tail may or may not persist in adults. (vii) Body wall has a single-layered epidermis.
(viii) Excretion is glandular.
(ix) Circulatory system consists of a ventral heart, blood vessels and sinuses. Blood contains both coloured and colour less corpuscles.
(x) Except in Herdmania, urochordates possess cells called vanadocytes. They can extract vanadium from sea water.
(xi) Cephalisation, appendages and segmentation are absent.
(xii) Starvation decreases the size of animals. They grow in size on availability of food (dedifferentiation). Urochordates resembling a small bag are also called ascidians.
Examples. Herdmania, Doliolum, Salpa, Ascidia, Ciona. A tunicate luminous at night is Pyrosoma.

Herdmania (Sea Squirt, Sea Potato)

It is sedentary, gregarious, filter/ciliary feeder ascidian. The body is flat like a purse with a length of 6-13 cm and breadth of 4- 7 cm. It is brownish in colour. The animal is partly buried in sand by means of foot. The remaining tunic is wrinkled. It has two apertures - branchial/incurrent/mouth and atrial/excurrent/cloaca. Each pore is surrounded by four lips or lobes. Digestive tract is complete. A branchial sac with gill slits is present. A current of water is passed through pharynx for picking up food. The current is maintained by cilia bordering gill slits or stigmata. On being disturbed, Herdmania emits a stream of water - hence its name of Sea Squirt. Herdmania is bisexual or hermaphrodite. It shows retrogressive metamorphosis during its development from tadpole larva.

Subphylum Cephalochordata or Acrania (Gk. kephali - head, chordata - with notochord)

(i) Notochord extends throughout the body and persists throughout life.
(ii) Dorsal hollow nerve cord is present.
(iii) Gill slits are present. They open into atrium.
(iv) Tail is present.
(v) Excretory organs are protonephridia with solenocytes.
(vi) Epidermis is single-layered.
(vii) Head is absent. Body is differentiated into trunk and tail.
(viii) Appendages are absent though fins may occur.
(ix) Blood is without respiratory pigment.
(x) Hearl is absent but circulatory system is present. Example. Branchiostoma/Amphioxus.

Branchiostoma (=Amphioxus, Lancelet) It is a burrowing protochordate animal which occurs in shallow water of sandy coasts. The anterior end is kept out of burrow.
The animal is 4-5 cm long laterally compressed spindle-shaped and whitish translucent. Head is absent but trunk is prolonged into snout or rostrum. Mouth is ventral and anterior. It is covered by oral hood having several oral tentacles or cirri.
Sense organs are unpaired and simple. They include ocelli, papillae, Kolliker's pit and infundibular organ. Posterior end bears two apertures, anus at the base of caudal fin and atriopore in the mid posterior region. Beyond it is present the tail. Branchiostoma has a dorsal fin, a caudal fin and ventral fin.
Ciliated larva occurs in the life cycle. The animal is a filter feeder. It has an internal wheel organ in the vestibule for producing a current of water.
Branchiostoma is eaten in China and Japan.

Vertebrata

They are sense organs made of sensory cells arranged lengthwise on either side of the body in fishes and some aquatic larvae. Lateral line organs detect vibrations (rheoreceptors) and electric fields generated by other organisms. Sensory cells are epidermal in origin. They are called neuromasts. They occur in groups in gelatinous cupulae embedded in epidermis.

Class Chondrichthyes (Cartilaginous Fishes)

The class consists of about 600 species of marine fishes which are characterised by
(i) Endoskeleton is cartilaginous. Fins are supported by horny fin rays.
(ii) Mouth is ventral.
(iii) Caudal fin is asymmetrical or heterocercal.
(iv) Dermal scales are placoid.
(v) Respiratory system consists of 5 - 7 pairs of lateral or ventral gill slits without any cover or operculum. An air bladder is absent. As a result cartilaginous fishes 'have to swim all the time to prevent sinking.
(vi) External nares lead into olfactory sacs. However, internal nares are absent.
(vii) Intestine has an anticlockwise scroll valve for increasing surface area.
(viii) Fertilization is internal.
(ix) Digestive tract leads into cloaca.
(x) Males possess claspers.
(xi) Ovovivipary generally occurs.
Examples. Scoliodion, Torpedo, Trygon, Pristis. Truely cartilaginous fishes are called elasmobranchs. Cartilaginous fishes with operculum are called holocephali (e.g., Chimaera). Remaining cartilaginous fishes are divided into two groups-pleurotremata of sharks and hypotremata of skates and rays. In sharks the gill slits are lateral. Pectoral fins are constricted at the base while the body is spindle shaped. Sharks are very active swimmers. Skates and rays have dorsoventrally flattened body, ventral gill slits and enlarged pectoral fins fused with sides of head and body.

Sharks

Body is spindle-shaped. Gill slits occur laterally. There are above 250 species. Size varies from 30 em to 16 m. The smaller sized sharks (below the size of 1 m) are called dog fishes. Common Indian Dog fish is Scoliodon. It is found along Indian coast. Length is 60 em. Dorsal side is greyish while ventral side is whitish. Some dog fishes possess a prominent spine with dorsal fins. Dog fishes are often bottom swimmers feeding on mixed diet containing crustaceans and molluscs. They live in both tropical and temperate seas.
The larger sharks (e.g., Syllum commonly live in warm waters. They are characterised by sharp sight and smelling power, great muscular strength, agility, strong jaws with sharp acrodont teeth (modified placoid scales). Sharks feed on other fishes, crustaceans, molluscs and sea urchins. They also attack human beings. Great White Shark (carcharodon Carcharias), a man eating shark reaches a length of 12 m. Indian shark which is equally ferocious is Carcharinus gangenticus. It is a menace to bathers in Hoogly at Kolkata. Swimming is forbidden in shark infested beaches as of S.W. Pacific ocean, and Eastern Australian beaches. Electronic and aerial.patrols are used to locate shoals of sharks and warn the people living along beaches. However, some very large sharks (e.g., Whale Shark Rhincodon, Basking Shark Cetorhinus) are filter feeders straining sea water with the help of filamentous gill rakers. They are also sluggish. In sharks, the head is dorsoventrally flattened. Mouth and nares are present on the lower side while gill slits are present laterally. The skin is very rough due to the presence of partially embedded pointed placoid scales. Male has claspers, attached to pelvic fins. Sharks possess backwardly pointed homodont teeth to prevent escape of prey. They are not meant for mastication. Shark liver is rich source of vitamin A.

Torpedo (Electric Ray)

It is a bottom dwelling carnivorous fish which has a smooth skin, and a flat almost circular trunk with fused pectoral fins. Mouth, nares and gill slits occur on the ventral side. Eyes and spiracles (for intake of water) occur on the dorsal side which also possesses a pair of electric organs (modified branchial muscles) for stunning the prey. Pelvic fins occur on the tapering part of trunk. The latter also bears two dorsal fins. Tail ends in a caudal fin.

Trygon (Sting Ray)

It has a flattened kite-like trunk with a long tail. Skin is smooth. Ventral side bears mouth, nares and gill slits. Dorsal side has eyes and spiracles. Pectoral fins are large to form the sides. A spine or stinger occurs on the tail. It is modified dorsal fin. Stinger or spine inflicts a painful deep wound on the prey.

Pristis (Saw Fish)

It is large fish with an elongated saw or rostrum reaching 1- 2 metres. Rostrum is enlargement of snout and bears 16 - 32 pairs of teeth.
Chimaera (Rabbit or Rat Fish)
Chimaera has a blunt conical snout, large pectoral fins, elongated single dorsal fin and four gill slits covered by operculum on each side. In adults the skin is smooth. Tail is long and whip-like. Anus and urinogenital apertures are distinct. Male has three types of claspers-frontal (= cephalic) clasper, a pair of anterior pelvic and a pair of posteior pelvic claspers. Chimaera is connecting link between cartilaginous and bony fishes.
Shagreen It is rough skin of sharks used for polishing.
Isinglass. It is white, transparent, almost pure gelatin obtained from swim bladders of some fresh water fishes (also hoofs) for making jellies, clarifying liquors, glue, etc.
Cod/Shark Liver Oil
Oil extracted from liver of Shark and Cod (e.g., Gadus callarias) is rich in vitamins A and D.
Class Osteichthyes (Bony Fishes)
The class consists of marine as well as fresh water bony fishes which number about 25,000. They have a variety of shape, size and colour. A number of fresh water forms are maintained in aquaria. The important characteristics are as follows.
(i) Endoskeleton is bony.
Fins have cartilaginous or bony fin rays.
(ii) Mouth is terminal. (iii) Caudal fin is generally homocercal. Dorsal fin is single. Pelvic fins are anterior.
(iv) Dermal scales are overlapping and can be of three types -ganoid, ctenoid and cycloid.
(v) Alimentary canal leads to anus.
(vi) A swim or air bladder commonly occurs. It helps the fishes to stay at particular depth in water without any expenditure of energy.
(vii) Four pairs of gills are covered by opercula.
(viii) External nares lead into olfactory sacs but internal nares are absent.
(ix) Mostly oviparous. Fertilization is external. Some species build primitive types. of nests for laying eggs. They also take care of the eggs till hatching. In Sea Horse, the male has a brood pouch in which the female lays eggs. The eggs remain there till they hatch. Bony fishes are also called teleosts (teleostomi).
Examples. Labeo, Catla, Anabas, Exocoetus, Solea, Anguilla, Hippocampus, Diodon (Porcupine Fish), Lates (Bhetki), Puntius, Heteropneustes, Channa, Lophius, Echeneis.
Catla Calla (Katla, Theila)
A large herbivorous bony fish of Indian rivers which reaches a length upto 1m. Body is spindle-shaped, greyish black above and silvery white below. Head has an upturned mouth, prominent lips, round eyes followed by a large operculum. The body is arched or convex dorsally. Dorsal fin is large and directed backwardly. Pectoral, pelvic and ventral (anal) fins are small. Caudal fin is also prominent and forked.
Heteropneustes ( = Sacchobranchus) fossilis (Singhi)
It is a carnivorous fish of muddy fresh waters. Body length is 30 cm. Head is flattened. Mouth is terminal. Operculum is small. Head bears four pairs of long barbels. Body is without scales. Dorsal fin is small. Pectoral fins bear poisonous spines which can inflict injury to the prey and other animals. The ventral anal fin is very long. It reaches upto caudal fin. Caudal fin is rounded. There is a special respiratory chamber.
Channa or Ophiocephalus punctatus (Lata Fish, Mullet, Daula)
It is a greenish white carnivorous fish of ponds, pools, rivers, etc. which can hibernate in mud during drought periods. During hibernation it respires through special respiratory chambers present above the pharynx. The fish is subcylindrical in outline with compressed posterior half and snake-like depressed head. Length is 30 cm. Scales are present. Both dorsal and ventral fins are long. Caudal fin is rounded.
Lates (Bhetki)
It is an inhabitant of estuaries but may also occur occassionally upstream in fresh water streams. The body is perfectly spindle-shaped in outline with a wide terminal mouth. Vomerine and palatine teeth also occur along with maxillary teeth. Caudal fin is fan-shaped. Dorsal fin has anterior and posterior parts. The fish feeds on fries and crustacean larvae.
Labeo (Fresh Water Carp, Rohu, Calbasu)
Labeo rohita (Rohu) and Labeo calbasu (Calbasu) are the common fresh water edible carps found in rivers and streams. Fin rays are soft. The carp reaches a length of 90 cm. The body is grey above and silvery white below. It is covered by large overlapping cycloid scales. Head is depressed and scaleless with subterminal mouth and a pair of short barbels. The fish is herbivorous but in the juvenile stages it is carnivorous.
Cat Fish (Rita rita, Clarius batrachus, verno Magur)
Indian Cat Fish (Clarius batrachus) lives in ponds. It is carnivorous. The head bears sensory threads called barbels. The body is smooth and without scales. Other fresh water cat fishes of India are Mystis seengala (= singharee), Rita rita (.= Tikanda = Khagga) and Wallogonia attu (= Mullee).
Climbing Perch (Anabas testudineus, vern. Koi)
It is a food fish found in rivers and estuaries, reaching a size of 20 cm. Head bears a number of small spines in front of eyes and along the opercular margins. Dorsal and ventral fins have stiff rays in the anterior region and soft rays in the posterior region. The fish can come out of water and creep on land by means of operculum and pectoral fins in search of small animals. Here it is often picked up by birds and taken to their nests (hence the belief of climbing). For remaining out of water, the fish gulps in air and stores it in accessory respiratory chambers.
Porcupine Fish (Diodon hystrix)
Marine. The body is covered by sharp, large, movable spines for defence.
Flying Fish (Exocoetus evolans)
It is a carnivorous fish of about 30 cm length which has very large eyes and very large pectoral fins inserted dorsally. Tail fin is forked, with upper lobe being smaller than the lower one. Flying fish is known so because it can leap into air by powerful tail and remain air borne for long distances due to gliding by means of large pectoral fins.
Flat Fish (Solea)
It is a bottom dwelling carnivorous fish which has flat laterally compressed body. Head is asymmetrical and bears both the eyes on one side though they are situated laterally in the embryo. Pectoral and pelvic fins are reduced. Dorsal and ventral fins are elongated. Caudal fin is small and non-bifurcated. Pleuronectes is another flat fish with ctenoid scales above and cycloid scales below. Sucker Fishes (Remora, Echeneis)
Marine typical fishes of upto 50 cm length. Scales are minute. Swim bladder and finlets are absent. The anterior part of dorsal fin is modified into transversely lamellate sucker for fixing to the under surface of sharks, other fishes, turtles, whales and other floating objects. Periodically it leaves its space host to capture and feed over small fishes. Sucker fish attached to shark, feeds on the left-over of shark's prey. The relationship is that of commensalism or ectocommensalism.
Lophius (Angler Fish, Frog Fish, Devil Fish)
It is a bottom dweller ugly looking marine fish which has a scaleless leathery skin with a number of flaps mimicking leaves of aquatic plants. Eyes are dorsal. Head and anterior part of body are enlarged. Mouth is wide. Teeth are sharp and recurved. They are covered by pigmented skin for camouflage. Dorsal fin consists of a few isolated rays or spines. The first spine or ray is present over the head. It bears a fleshy mass or bulb at its tip to act as bait. Many parts phosphorescent to attract preys. Pectoral fins are broad and pediculate. They are used for moving over the substratum.
Gambusia (Mosquito Fish, Top Minnow)
The fish feeds on mosquito larvae (larvaevorous) and is, therefore, used as larvicidal. Some other larvaevorous fishes are Labestes, Oryzias and Telapia.
Eel (Anguilla benga/ensis)
The fish has an elongated and cylindrical body with no pelvic fins and small pectoral fins. Dorsal and ventral fins are continuous with caudal fin. Adult lives in fresh water and estuaries. It migrates to ¬ocean for spawning (catadromous). The young eel migrates back to fresh water. It is known as elver.
Spotted Eel'(Muraena) is larger eel which may ascend tidal rivers. It feeds on other fishes. At times it attacks even human beings.
Sea Horse (Hippocampus guttalatus)
It is most peculiar bony fish which swims vertically. The body is covered with bony shields having tubercles, spines and filaments. Head looks like that of horse. It is prolonged into tube like snout with terminal mouth. Head lies at right angles to body. Tail is prehensile. Male bears a brood pouch for keeping the eggs till young ones hatch out of them (hence pregnant male). Pelvic, ventral and caudal fins are absent. Pectoral fins are reduced. Dorsal fin is soft and present in the middle of back.
Lung Fish (Mud Fish)
The common lung fish of Australia is Neoceratodus, of America Lepidosiren while that of Africa is Protopterus. They are sometimes placed in a separate class of Choanichthyes. Internal nares are present. Heart approaches the 3-chambered amphibian form. Notochord is persistent. Paired fins have elongated jointed axis and bear jointed rays. Dorsal and ventral fins are continuous with caudal fin. Gills are reduced. There is no spiracle. Air bladder forms a single or double lung. Teeth produce crushing plates. Lung fishes live in shallow waters. They can creep or walk by means of paired fins. Swimming is done like eels. The fishes are carnivorous.
Latimeria (Coelacanth)
It resembles lung fishes in having internal nares, lobed fins and lung or air sac. Latimeria was discovered in 1939. All its fins except the two dorsal ones are lobed. There are two pairs of external nares. Heart is, however, primitive. Notochord is massive and cartilaginous. It swims by rotating movement of its pectoral fins. Swim bladder is vestigial. Latimeria is called living fossil as it has remained unchanged for several million years.
Lobe-finned lung fishes are believed to be fore-runners of tetrapods.
Fresh Water Food Fishes.
Labeo rohita (Rohu), Labeo calbasu (Calbasu), Catla catla (Catla), Rita rita (Cat Fish), Cyprinus carpio (Carp), Clarius, Cirrhina mrigala (Mrigal), Wallogonia attu (Mullee = Malhi), Ophiocephalus puctatus (Chauna), Notopterus chitala (Chital).
Common Marine Food Fishes.
Hilsa (Hilsa), Anguilla (Eel), Harpodon (Bombay Duck), Sardinella (Salmon), Stromaterus (Pomphret), Dussumieria (Sardine), Exocoetus (Flying Fish), Scomber (Mackerel).
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Class ─ Amphibia
Amphibia is the class of tetrapoda which have aquatic larval stage and terrestrial adult stage. They were the first tetrapods to evolve during devoniano Tetrapoda is the superclass of four-footed animals where the limbs are pentadactyl or with 5 digits. Tetrapods are divisible into four classes - amphibia, reptilia, aves and mammalia.
Characteristics
(i) Amphibia includes anamniotes (without amnion), poikilothermal or ectothermal animals (cold blooded in which temperature of the body varies according to that of surroundings) which live both in fresh water and moist soil. Marine forms are absent.
(ii) Larval stage is fish-like (tadpole) which is aquatic. It has a tail for swimming. Adults are morphologically different from larvae. They usually live on land. Breeding requires water environment. Therefore, amphibians though adapted to terrestrial life, have to be near water for completing their life cycle.
(iii) Body is divisible into head and trunk. Neck is absent.
(iv) Eyes have eyelids.
(v) Middle ear is present. Tympanum lies on the outside to receive vibrations. (vi) Reproductive, urinary and digestive tracts open into common cloacal chamber or cloaca. It leads to exterior through a cloacal aperture or vent.
(vii) Skin is naked i.e., without scales. It has glands and is kept moist.
(viii) The animals have two pairs of pentadactyl limbs. They are used for walking and swimming. Fore limbs generally end in four digits while hind limbs have five digits without scales. Digits do not have claws nor nails. They may be webbed.
(ix) Heart is three chambered. It also bears sinus venosus and truncus arteriosus. Both renal and hepatic portal systems are present. RBCs are nucleated.
(x) Gills occur in larval stage which may also possess unpaired fins. Gills occur in some adults in addition to lungs. Respiration can also occur through skin and buccal cavity.
(xi) Cranial nerves are 10 pairs.
(xii) Nitrogenous excretory product is usually urea.
(xiii) Kidney is mesonephric but the tadpole has pronephric one.
(xiv) Skull is dicondylic. Vertebrae are procoelous (concave at the anterior end of the centrum and usually convex at the posterior end of the centrum)..
(xv) Sexes are separate. Fertilisation is external. Larva undergoes metamorphosis. Amphibia is usually divisible into three orders - apoda, anura and urodela. Carboniferous is the age of amphibians.
Order Apoda (Caecilia, Gymnophiona)
(i) Limbs, girdles, neck, middle ear and vocal cords are absent. Tail is nearly absent.
(ii) The animals are worm- like, apparently segmented with head and trunk.
Head bears sensory tentacles.
(iii) Eyes are functionless.
(iv) Dermal scales are embedded in skin.
Examples. Ichthyophis, Uraeotyphlous.
Ichthyophis (Caecilian)
It is limbless amphibian of 15 - 22 em length that lives in burrows in moist soil. Mouth is wide. Eyes are covered by opaque skin. Sensory tentacles occur between nares and eyes. Dermal scales occur. In males, cloaca is eversible to act as copulatory organ. Eggs are protected by female. They hatch into tadpoles.
Order Urodela (Caudata)
(i) Animals have head, neck, trunk and tail. The tail may have caudal fin withp,ut fin rays. (ii) Skin is smooth. (iii) Middle ear and vocal cords are absent but eye lids occur. (iv) Gills and gill slits may occur even in the adult. Examples. Necturus, Salamandra, Amphiuma (Congo Eel). The largest amphibian is Cryptobranches (Hell Bender).
Necturus (Water Newt, Water Dog, Mud Puppy)
It is 30 cm long bottom dweller of lakes and rivers of North America. Head has eyes but without eye lids. Tympanum is absent. There are three pairs of external gills and two pairs of gill slits. Tail is laterally compressed and has a tail fin devoid of fin rays.
Mud Eel (Siren lacertina)
It is an amphibian with an elongated body, four-digited short fore limbs, hind limbs absent, presence of two types of gills - three pairs of external and three pairs of gill slits. Congo Eel (Amphiuma) is another eel-like amphibian.
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Salamander (Salamandra, Ambystoma, Triturus, Tylotriton or Indian Salamander)
It is a semiterrestrial lizard-like tailed carnivorous and nocturnal amphibian. Salamander lives under stones, logs and inside crevices. Parotid glands occur. Tail is used for swimming in water. It is without a fin except in Triton. During breeding season Triturus develops lateral line organs. Its tail also becomes flattened. Salamanders may be oviparous or ovoviviparous. The aquatic larva or tadpole is called axolotl. The same has external gills, lateral line organs, and compressed tail with caudal fin. Axolotl may remain in the larval stage indefinitely if water and food are plenty. It may develop sex organs and start breeding. The phenomenon is known as Neoteny. An axolotl larva exposed to air loses gills and tail fin, develops lungs and becomes adult Salamander.
Order Anura (Salientia)
The order includes common amphibians, frogs and toads.
(i) Body is divisible into head and trunk.
(ii) Fore limbs are short. Hind limbs are long. Webbed digits often occur for swimming,
(iii) Skin is smooth in frogs and warty in toads.
(iv) Vocal cords develop for the first time.
(v) Middle ear is present. (vvi) Fertilization is external. Larval stage or tadpole has gills and tail.
Examples. Rana, Bufo, Hyla, Alytes, Pipa, Bombinator.
Rana tigrina (Common Indian Frog, Indian Bull Frog)
It lives inside and around ponds, pools, ditches and streams. Body is divisible into head and trunk. Head has a wide semicircular terminal mouth, large bulging eyes, circular tympanums and small external nares. Each eye has a nictitating membrane (in addition to upper and lower lids) to cover the eye ball and protect it in water and mud. Tongue is attached anteriorly. It is protrusible and sticky to catch insects, spiders, worms, etc. Frog is, therefore, carnivorous. Teeth (on upper jaw, maxillary and two patches of vomerine tteth) are meant for preventing escape of prey. Skin is moist due to mucus and dipping in water at intervals. It bears patches and wrinkles, on the back. A characteristic hump occurs in sitting posture. Fore limbs are short, stouter and end in four digits. Hind limbs are long and end in 5-webbed toes. Male has a nuptial or amplexusory pad on inner digit of fore limb for holding the female during amplexus. It also possesses two vocal sacs on the throat for croaking loudly. In winter, Frog undergoes hibernation (winter sleep inside mud for protection against low temperature) while in hot summer it shows aestivation (summer sleep in moist cold places). Amplexus occurs in water. Fertilization is external. Larva or tadpole passes through external gill and internal gill stages.
Bufo melanostictus (Indian Toad)
Toad inhabits dark shady and moist places in gardens, lawns, under stones, logs, etc. The animal is nocturnal. In rainy season it is quite common during evenings and nights. The animal resembles frog but does not have characteristic hump. The skin is greyish, dry and warty. The warts possess toxin glands (yielding bufotenin C12H16NzO, bufonin C34Hs40Z and bufotoxin C34H4601O) which seem to have healing powers for the animal. There is also a pair of large parotid glands behind the tympanums. The glands produce a mildly toxic milky secretion. Bufo visits water only fm breeding. Cutaneous respiration is absent. Male toad possesses one vocal sac but develops amplexusory structures on two inner fingers. The mouth does not contain teeth. Anteriorly attached tongue helps in catching prey as in Frog. Hibernation occurs similarly.
Hyla arborea (Green Tree Frog)
It has adhesive pads on the digits for climbing trees. Hyla shows mimicry. It is actually a toad.
Rhacophorus (Flying Frog)
The frog has adhesive pads as well as-webbed digits on hands and feet. It can jump great distances, climb walls and trees.
Alytes obstetricans (Midwife Toad)
The male collects the eggs around its legs and hides till hatching.
Pipa americana (Surinam Toad)
The back of female have several pouches for eggs. Feet possess large webs.

Bombinator or Discoglossus igneus (Fire Bellied Toad) It is a small sized amphibian found in Europe. Its under-stlsface contains irregular orange-red patches. The patches are used for terrorising enemies. In water, the ventral side appears as flames. On land the belly is exposed by bending the head and legs upwardly. A bissing sound is also produced.
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Reptilia is a class of subphylum vertebrata which comprises amniotic tetrapods with dry skin having epidermal scales and incompletely four chambered heart. Number of species is 6000. The name reptiles has been given to them because most present day forms are low statured and i.'ppear crawling. They are the first true land animals. Two features have helped them in becoming truely terrestrial- internal fertilisation and presence of foetal covering called amnion.
Group Amniota
It comprises three classes of vertebrates - reptiles, birds and mammals. All of them contain a special foetal membrane called amnion. Amnion encloses fluid and provides a watery environment for development of foetus so that the latter could grow outside the aquatic habitat and become truely terrestrial. All members of amniota have 12 pairs of cranial nerves. Larval stage and metamorphosis are absent.

Foetal or Embryonic Membranes
In amniotes, the embryo has four types of membranes-chorion, amnion, allantois and yolk sac. The first three are extra-embryonic. Chorion. It is the outermost membrane which lies below the shell of egg. In mammals, chorion becomes part of placenta. Amnion. The membrane surrounds the embryo and forms a fluid-filled amniotic cavity around it. Allantois. It develops from embryonic gut. Allantois forms a sac that is involved in excretion, respiration and nutrition. In mammals it produces blood vessels of the placenta. Yolk Sac. It is yolk storing sac that arises near the allantois. It forms blood corpuscles of embryo in mammals.

Characteristics of Reptilia
(i) It contains creeping, amniotic, poikilothermal (ectothermal) tetrapod vertebrates where post¬anal tail tapers gradually.
(ii) Skin is dry and cornified with epidermal scales or scutes.
(iii) Two pairs of pentadactyl limbs occur (secondarily lost in snakes). Digits end in horny claws.
(iv) Heart is incompletely (completely in Crocodilia) four chambered with two auricles and incompletely divided ventricle. Sinus venosus is present but truncus arteriosus is absent.
(v) Skull is monocondylic. Vertebrae are procoelous.
(vi) Sternum and ribs occur.
(vii) Kidney is metanephric. Excretory product is uric acid in terrestrial forms and urea in aquatic forms. (viii) Respiration is pulmonary. Cloacal respiration occurs in Turtles.
(ix) Cranial nerves are 12 pairs with a few exceptions.
(x) Cloaca is present. Cloacal aperture is transverse with the exception of crocodiles and chelones.
(xi) Some tortoises are herbivorous. Other reptiles are cart1!yorous or insectivorous.
(xii) Fertilization is internal. Mostly oviparous. Parental care is little. Reptiles were very abundant in mesozoic. The latter is, therefore, called age of reptiles. Dinosaurs occurred during this period. Jurassic is the age of dinosaurs. Besides dinosaurs, a number of other fossil forms are also known. Living reptiles fall in two subclasses, anapsida (without opening in temporal bones, e.g., order chelonia) and diapsida (with two temporal openings in skull, e.g., orders squamata, crocodilia and rhyncocephalia).
Reptilia has four orders - squamata, chelonia, crocodilia and rhyncocephalia.

Order Squamata
Cloacal aperture is transverse. Copulatory organs are paired (hemipenes) and eversible. Tongue is protrusible. Periodic shedding of dead hornified scaly skin is common. It is called skin cast. It includes two suborders, lacertilia (lizards) and ophidia (snakes).
Lizards (Lacertilia)
(i) Epidermal scales are of uniform size.
(ii) Jaw bones are fixed so that the gape is not very large.
(iii) Eyes have movable eye lids.
(iv) Tympanum is present.
(v) Tail vertebrae are not fused.
(vi) Tongue is not always protrusible.
Examples. Hemidactylus, Draco, Calotes, Ch am aeleon, Varanus, Uromastix (Sand Lizard), Ophisaurus (Glass Snake), Phrynosoma (Horned Toad), Helodenna (Gila Monster). The only marine lizard is Amblyrhnchus.

Hemidactylus (Wall Lizard, House Lizard, Gecko)
It is a common nocturnal and carnivorous (insectivorous) lizard found roaming over walls, especially, illuminated places. It hibernates during winter and hides during the day. Wall Lizard is about 15 em long with slightly flattened body divisible into head, neck, trunk and tail. Out of the _wo pairs of limbs, the hinder limbs are slightly longer. The digits end in claws. On the under-surface, the digits bear adhesive pads or lamellae. They work on vacuum principle and help the animal to walk over smooth walls and ceilings. Tongue is sticky and protrusible for catching insects. The lizard produces the sound of 'geko' or 'yeko'. It shows autotomy by breaking its tail when threatened. A new tail is regenerated. It is without tail vertebrae.

Draco (Flying Lizard, Flying Dragon)
The skin on either side of the trunk is expanded to form fan-shaped folds or patagia. Five ribs are involved in the process. Patagia help the animal in gliding. The lizard lives on trees. It is insectivorous. There are three soft hooks in the throat region. D. maculatus is the flying lizard of India.
Calotes (Garden Lizard, 'Blood Sucker')
Calotes versicolor or Garden Lizard is quite common in hedges, gardens and jungles. It has a light brown or grey colour. When excited, the colour of neck and head turns red while that of the trunk changes to pale yellow. In breeding season the male develops brilliant reddish pigmentation in the head region. The size is upto 35 em. Tail is long and prehensile. There is a middorsal crest of backwardly pointed scales. A feeble midventral crest also occurs in the neck region. The animal is insectivorous.
Varanus (Indian Monitor, Goya, Varanus monitor)
It is 60 - 90 em long lizard with powerful claws, stout limbs and laterally compressed tail. The animal lives in burrows as well as trees. It can swim actively as well. The tongue is long, protrusible and forked. Varanus is nocturnal and carnivorous feeding on squirrels, tortoises and others. Eggs are generally laid in hollows of tree trunks. V. komodensis (of Komodo Island) is the largest livingJizard with a length of 3 m and weight of over 100 kg. It feeds on animals of upto size of deer.
Chameleon (Chamaeleon zeylanicus, Girgit)
The lizard is famous for changing its colour according to its surroundings. The phenomenon is called metachrosis. Chamaeleon puffs and hisses on seeing an enemy. Chamaeleon is normally greenish black in colour with laterally compressed body having granular scales. Both mid-dorsal and mid-ventral rows of pointed scales occur. There is a prominent helmet over the head. Eyes are large but eye lids are fused leaving only a small area to see through. Tympanum is absent. Limbs are long and slender. Digits form two groups (zygotylous) for grasping. Tail is long and prehensile. The tongue is long, upto 30 em, and eversible. It is kept rolled up inside mouth. The tongue bears an adhesive bulb at its end for catching insects. Chamaeleon is ovoviviparous lizard.
Glass Snake (= Glass Lizard, Ophisaurus)
It is a limbless snake-like lizard of eastern U.S.A. which has a long and fragile tail that can be broken off and replaced. Anguis fragilis (Slow/Blind Worm) is another limbless lizard. The limbless lizards can be differentiated from snakes by their nonexpansible mouth, movable eye lids and ear openIngs.
Horned Toad (Phrynosoma cornutum)
It is burrowing insectivorous lizard of sandy arid areas of American continent which is characterised by mid-dorsal streak, keeled dorsal scales, five bony spikes on either side of head and small spines on the sides of lower jaw. Skin is hygroscopic and can absorb water from wet soil. On being irritated, the animal emits a jet of blood from eyes by contracting blood sinuses present at the base of nictitating membrane.
Gila Monster (Heloderma suspectum)
It is the only poisonous lizard which is found in dry areas of America. The animal is nocturnal, feeds on eggs and small lizards. The body has blackish colour with yellow-pink spots, bead-like dorsal scales and thick tail. Poison glands open into gum of lower jaw. Poison is neurotoxic.
Snakes (Ophidia)
(i) They are limbless reptiles with elongated cylindrical body.
(ii) The body is covered by overlapping scales which are differentiated into shields and plates. In nonpoisonous snakes the belly has small scales. Large hexagonal scales occur on the back in Krait (highly poisonous) while Viper (poisonous) has small scales on the head region.
(iii) Jaw bones are movable so that gape of mouth can be enlarged to swallow large sized prey.
(iv) Eyes are covered by transparent scales. Eye lids are not discernible. Tympanum and tympanic cavity are absent. Only ground waves can be picked up.
(v) Tongue is forked and narrow. It protrudes through a notch in lower jaw.
(vi) All the teeth are simitar and maxillary. They are non chewing. In poisonous snakes two maxillary teeth are enlarged, grooved or tubular. They are connected with poison gland (modified salivary glands, parotid and labial). They are called poison fangs and are concerned with injecting poison. A snake bite showing U-shaped teeth mark is thaf of nonpoisonous snake. Mark of two teeth indicates bite of a poisonous snake. Snake poison is of two types, neurotoxic (paralysis of nerves and muscles, e.g., Cobra, Krait) and hemotoxic (haemorrhage and destruction of blood, e.g., Viper). Immediate injection of antivenin (prepared by Hofkin's Institute Bombay) can save from otherwise sure death.
(vii) Right lung is reduced.
(viii) Olfactory organ bears a vomeronasal diverticulum or Jacobson's organ.
(ix) Urinary bladder is absent.
(x) Locomotion occurs by means of ventral scales, ribs and lateral body wall muscles.
(xi) Vocal cords are absent. Hissing sound is produced by expelling air through the nares.
(xii) Outer horny skin layer is periodically cast off. Examples. Rat Snake, Cobra, Python, Krait, Viper, Sea Snake, Blind Snake, Tree Snake (Dendrophis), Water Snake (Natrix). The most famous serpentarium of India is at Chennai.

Cobra (Naja = Naia tripudiens)
It is a diurnal highly poisonous snake that lives in holes, under stones, thick vegetation and rat infested areas. Cobra is carnivorous and feeds on frogs, rats, lizards, birds, etc. The colour is brown or black. Length is 1. 5 - 2 m. King Cobra (Naia hunnah) may reach a length of 5 metres. The ribs of the neck region can spread to form hood. Hood may be noncellate, monocellate (one circular mark) or bicellate (spectacle-like double mark). When alarmed, Cobra erects the anterior one-third part of the body. The hood is also expanded. At this time it produces a hissing voice. The erect part swings forwards and backwards. Cobra venom is neurotoxic. It, however, possesses anticancer properties.
Python (Ajgar, Python molurus, P. reticulates
It is the largest reptile reaching a length of 9 -10 metres. Python lives on trees in forests, rocky and sandy places. It can also swim. The body is cylindrical, greyish brown with red and black spots. Head is distinct. There is a small prehensile tail. Claw-like spurs occur on the sides of cloaca representing vestigial hind limbs. Python is nonpoisonous. It is carnivorous and feeds on a number of animals, including deer, goats, pig, etc. Python first kills the prey by coiling around it. The crushed prey is then swallowed.
Rat Snake (Dhaman, Ptyas mucosus)
It is a nonpoisonous snake of up to 2.5 m length with greenish or greenish brown black. The snake feeds on frogs, toads, lizards, rats, etc. Rat snake is a good runner and swimmer. Its fat is used in leprosy treatment.
Double Headed Snake (Sand Boa, Eryx johnii)
It is nonpoisonous brown-coloured snake with small pointed head and blunt tail. The tail end is often mistaken for the second mouth. The prey is first killed by constriction before swallowing.
Blind Snake (Typhlops braminus)
It is a nonpoisonous (25-30 cm) dark brown or blackish snake which lives in self dug burrows and is insectivorous. Mouth is with small gape. Head is indistinct. Eyes are vestigial. Tail is short. Tree Snake (Dendrophis) is nonpoisonous.
Krait (Bungarus species)
Kraits are highly poisonous snakes. Common Krait has black or steel grey colour with white arches on the back. In Banded Krait the body has alternate broad bands of black and yellow colours. Central scales of back are larger and hexagonal. Kraits usually occur in pairs and are nocturnal.
Viper (Russel's Viper, Viper russel/i)
It is poisonous snake with triangular head having V -mark. Back has three rows of black spots. Pits have infra-red or heat sensitive organs for location of prey.
Sea Snake (Hydrophis species)
Generally poisonous with laterally compressed tail for swimming. Sea Snake feeds on small fIShes. Head is kept erect while swimming. Nostrils are valvular. The snake is ovoviviparous.
Order Rhynchocephalia
(i) Remnants of notochord occur in intervertebral spaces.
(ii) Copulatory organs are absent.
(iii) Parietal or third eye is present in the middle of fore-head. Example. Sphenodon.
Sphenodon (Tuatara)
Sphenodon (= Sphaenodon) punctatum (tuatara) is the only living representative of order rhynchocephalia found in New Zealand. It is living fossil. The animal lives in burrows but is semi-aquatic, nocturnal and carnivorous. It reaches a length of 75 - 90 em. It has a mid-dorsal crest of slightly erectile spiny scales. Tail is laterally compressed. Upper jaw has a horny beak. There is a medium or third eye on the fore-head. It resembles the functional eye in having lens, retina and nerve supply but is covered with scales.
Order Chelonia (= Testudia)
(i) Trunk is broad and covered with a shell made of dorsal carapace and ventral plastron.
(ii) Jaws are toothless. They have horny sheath for crushing food.
(iii) Limbs may end in horny claws, have webs or get modified into flippers.
(iv) Terrestrial or aquatic. Aquatic forms possess vascular sacs in cloaca.
Males have copulatory organs on ventral wall of cloaca. Longest life span amongst animals is that of members of chelonia (upto 200 years). Giant Tortoise may weigh upto 600 kg.
Examples. Testudo
Trionyx,' Chelonia.
Terrapin (Fresh Water or Soft Shelled Turtle, Trionyx gangeticus)
It occurs in ponds and rivers. The shell is almost circular and covered with soft skin. Trionyx gangeticus has olive-green carapace and yellowish plastron. Head is produced into a proboscis. Neck forms S-shaped curve when retracted. Head is greenish with black streaks. Limbs are webbed with some digits bearing claws. Terrapin is carnivorous. Head and limbs can be completely withdrawn under the shell. Pond turtle is Lissemys.

Tortoise (Testudo species)
It can walk slowly on land as well as swim in water. Tortoise is herbivorous but may take in worms and insects. The animal hibernates in winter and passes hot summer in water. The shell is ovoid and covered with horny scutes. Carapace is domed. In Testudo elegans the scutes are humped. They possess yellow radiations (hence Starred Tortoise). Digits bear claws. Head and limbs can be completely withdrawn inside the shell.
Green Turtle (Chelonia species)
It is found in sea. Size is upto 1 metre. Green Turtle feeds on sea weeds but occasionally turns carnivorous. Fat is green. .Carapace is low and heart-shaped. Limbs are modified into paddles. Head cannot be withdrwan completely under the shell. Green or Marine Turttle comes to the coast for basking and laying eggs.
Order Crocodilia (= Crocodylia)
(i) It includes large-sized fresh water aquatic reptiles where the body is covered by horny epidermal scales supported by bony plates.
(ii) Like mammals, the heart is four- chambered. An incomplete diaphragm is found between thorax and abdomen. Teeth are thecodont. Internal nares are pharyngeal.
(iii) Eyes, nostrils and ear occur in straight line high on the head.
(iv) Digits are webbed and clawed.
(v) Male has a copulatory organ.
(vi) Urinary bladder is absent.
(vii) Tail is laterally compressed for swImmIng.
Crocodile (Muggar, Crocodi/us/Crocodylus palustris)
It is dreaded reptile of marshes, tanks and rivers which reaches a length of 3 - 4, 5 metres. The upper surface is dark brown with black spots or bands. The snout is prolonged and triangular. Teeth are unequal. They are not used for mastication. Crocodile is carnivorous. It feeds on fish and other animals. C. niloticus of Africa preys on larger land animals including human beings passing along streams. Crocodile comes on land for basking, laying and protecting eggs. Swimming is done by laterally compressed tail and webbed hinder limbs.
Gavial (Gharial, Gavialis gangeticus)
Gavial is found in rivers. The upper surface is green. Snout .is very long bearing a pot like enlargement in males. Teeth are unequal. The animal is carnivorous. It may reach a length of 6 metres.
Alligator (Alligator species)
It is found in China and America. Alligator has steel grey upper side and green lateral sides. Snout is blunt. Teeth are very unequal. It is carnivorous and resembles Crocodile in its habits.
Order Saurischia
It is the order of reptilian dinosaurs or terrible lizards which lived about 70-170 million years back and dominated the earth. Hind limbs were longer and stronger. Tail was long and stout.
Brontosaurus (Thunder Lizard)
It was the largest dinosaur (largest land animal) which lived in swamps and walked on all the four limbs. Brontosaurus was herbivorous. It had a length of 20-25 m, a height of 4-5 m and weight of 40-50 metric tonnes. Both neck and tail were very long.
Tyrannosaurus (Tyrant Lizard)
It is also known as king of dinosaurs. Tyrannosaurus was carnivorous. It had powerful jaws. Gait was bipedal. Body was supported by tail. The fore limbs were smaller. Tyrannosaurus attained a height of 6 m and length of 16 m.
Order Ornithischia
The order includes those dinosaurs which had horny beaks and bird-like pelvis, e.g., Ankylosaurus, Stegosaurus.
Stegosaurus (Plated Lizard)
The animal had two rows of erect bony plates on the back and bone like spines on the tail. Stegosaurus was terrestrial, herbivorous and 4-legged but the hind limbs and tail were very strong. Head was comparatively smaller. The dinosaur reached a length of about 6 metres.

Aves

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Aves are warm blooded tetrapods in which the fore limbs are modified into wings, the body is covered by feathers and the jaws are modified into horny beaks. Birds are, therefore, bipedal, winged and feathered animals. Birds evolved in Jurassic about 150 million years ago from ornithischian dinosaurs. Early birds (e.g., Archaeopteryx) had toothed beaks. Modern birds appeared in cretaceous. Because of their origin from reptiles, Huxley has called birds to be glorified reptiles. Birds and bony fishes are the two most successful classes of vertebrates. Number of bird species is about 9000.
Characteristics
(i)Fore-limbs are modified into wings. Three unarmed digits occur in them. They are, however, not visible externally. The body is supported on hind limbs. They are covered by scales. The hind limbs generally possess four toes which end in horny claws. Toes are generally zygodactylous or arranged in two groups. Pelvic girdle is long for supporting hind limbs to bear body weight.
(ii) Body is covered by feathers. They are modified scales which help in flight as well as insulation of body. Skin is dry except for the presence of an oil or preen gland at the base of short tail or uropygium. Sweat glands are absent.
(iii) Bones are pneumatic i.e., they possess air passages. This reduces body weight. Bone marrow is absent. Skull bones, vertebrae of trunk (thoracic, lumbar) and tail are fused. Fused tail vertebrae form a structure called pygostyle. The forked bone furcula formed by the fusion of two clavicles is called wish bone.
(iv)Jaws lack teeth. They are prolonged and covered with horny sheath or rhampotheca to form beak. Gape is wide. Beak is modified variously for wood chiseling, seed crushing, fruit scooping, flesh tearing, nectar sipping, straining, etc.
(v) Alimentary canal contains crop (modified oesophagus) for storing and softening of food and gizzard (grinding part of stomach, the other glandular part being proventriculus) for crushing it. Pigeon milk is secretion or product of crop formed in both sexes for feeding the young ones.
(vi)Pectoral girdle is strong. Sternum is large and has well-developed keel (except in some flightless birds) for attaching flight muscles. Skull is monocondylic. Vertebrae are heterocoelous.
(vii) Lungs are spongy but inelatic. They are associated with elastic air sacs lying amongst the viscera.
(viii) Larynx is nonfunctional. Instead syrinx occurs at the junction of trachea and bronchi.
(ix)Heart is four-chambered. Brain is well developed. Balancing and coordinating regions are particularly enlarged. Cranial nerves are 12 pairs. Eyes possess a comb-like structure or pecten in the form of network of blood vessels from blind spot in all birds except Kiwi. This structure is also found in reptiles. Eye sight is keen for locating food, prey, nest, landmark, etc. from a height while flying. However, the sense of smell is poor. Pinnae are absent.
(x) Kidney is metanephric. Excretory system is without urinary bladder (exception Ostrich, American Rhea). Major excretory product is uric acid. It is passed into cloaca.
(xi) Bursa fabrici is a lymphoid tissue attached to cloaca of some young birds which takes part in formation of lymphocytes. It is also called cloacal thymus.
(xii) In females, the ovary and oviduct of only left side are present. Fertilization is internal. Sperm transfer occurs by approximation of cloacal aperture of female with that of male. Animals are oviparous. Eggs are large sized and full of yolk. They are cleidoic or covered by calcaerous shells.
(iii) Birds are homoiothermal or capable of keeping their body temperature constant. Metabolic rate is high. Poorwill /Night Jar/Goat Sucker (Caprimulgus europeus), a short billed wide mouthed nocturnal insectivorous bird undergoes hibernation.
(xiv) Parental care is elaborate. Most birds build nests for laying eggs, their incubation and rearing of young ones. Indian subcontinent is rich in avian fauna. Some common Indian birds are Pheasant, Bulbul, Owl, Koel, Parrot, Peafowl, Vulture, Hornbill, Crane, Spoonbill, Hoopoe and Swan.
Class aves is divisible into two subclasses - archaeornithes (extinct toothed birds, e.g., Archaeopteryx) and neornithes (true birds).
Neornithes is distinguished into flightless (ratitae, palaeognathae) and flight (carinatae, neognathae) birds. In flightless birds the wings are reduced. Sternum is without keel. A syrinx is absent. Penguins are now included in separate group (impennae) of their own. Smallest bird is Cuban/Bee Humming Bird (Mellisuga helenae, length 5.5 cm).The largest bird is Ostrich or Struthio camelus camelus (height 2.5 - 2.7 m). Its egg is also the largest (1.5 litre capacity). Their largest wing span (upto 5 m) occurs in Albatrosses, The fastest flying bird is a Swift (Micropodus) with a top speed of 320 km/hr and ability to fly nonstop for 800 km. 00
Feathers in Birds
They are of six types - quills, coverts, filoplumes, down and bristles. v 1. Quills (Flight Feathers). They are large feathers of wings (remiges) and tail (retrices). A quill has a shaft differentiated into hollow proximal calamus and distal solid rachis. Rachis bears vane or vexillum made of parallel filaments called barbs, Barbs possess barbules. Barbules have hooklets or barbicels and grooves or flanges.
2. Coverts. They are small feathers similar to quills meant for filling gaps on the wings and tail.
3. Contours. They are small feathers that cover the body. Their barbs can be easily separated.
4. Filoplumes. The feathers occur beneath contours. Each filoplume consists of a calamus having a few weak barbs at the tip.
5. Down Feathers. They cover the body of a newly hatched bird (nestling downs). Down feathers also occur beneath contours (powdery downs), Each down feathers has a small calamus and a few long flexible barbs containing barbules without interlocking hooklets.
6. Bristles. They occur at places. Each has a short calamus, a long naked rachis with a few vestigial barbs at the base.
Pterylosis (Ptilosis) Arrangement of feather tracts (pterylae) and naked or down-covered areas (apteria). Bastard Wing (Ala Spuria). Bastard or false wing is a tuft of small feathers present on the first digit or thumb.
Beaks of Birds
Beaks are modified variously to perform different functions:
(i) Elongated for sucking nectar in Sun Bird and Humming Bird.
(ii) Digging earth and catching insects in Hoopoe.
(iii) Opening of crevices on trees to pick up insects in Wood Pecker.
(iv) Straining in Duck.
(v) Broad and elongated for picking up aquatic vegetation in Spoonbill.
(vi) Crushing seeds and grains in Sparrow.
(vii) Eating (scooping) fruits in Parrot and Hornbill.
(viii)Tearing flesh in Hawk, Falcon, Owl, Kite, Vulture.
(ix) Elongated and pointed in Heron and Cormorant for catching fish.
Toes of Birds
(i) Webbed toes in water birds.
(ii) Elongated toes for walking over floating leaves in Jacana and wading in Jacana and King Fisher.
(iii) Clinging and climbing in Wood Pecker.
(iv) Perching in most birds.
(v) Raptorial, grasping and striking in Hawk and other birds of prey.
(vi) Walking, scratching and fighting in Fowl.
(vii) Running in Ostrich.
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Bird Migration
There are two types of birds - migratory and local/resident. Migration is of three types - daily, seasonal (Gulls, Flemings, Waders, Stork, Swallows, Plovers) and cyclic (Snow Owl). Longest distance traveled is by Arctic Tern (Sterna parasisaea) from arctic to antarctic and back (17600 km). Golden Plover flies nonstop for 3600 km and uses only two ounces of high octane fuel. Bird migration is studied by ringing or banding.
Archaeornithes
Archaeopteryx (Lizard Bird).
Archaeopteryx lithographica is an extinct primitive bird which existed on earth some 150 million years back (Wagner, 1861). It had a size of crow. Archaeopteryx possessed wings (modified fore limbs), feathers, bipedal gait and prolonged jaws or beak. However, it contained teeth, keel-less sternum, long tail with unfused vertebrae (pygostyle absent) and claws on the fingers. Digits of the wings are separate. Presence of both reptilian and avian traits in Archaeopteryx indicates that birds have evolved from reptiles. It seems that in Archaeopteryx the wings helped in gliding instead of flying.
Ratitae or Palaeognathae (Flightless Birds)
Ostrich (Struthio camelus)
It is the largest living bird. It is flightless. Ostrich is gregarious, polygamous and omnivorous bird found in Arabian and African deserts. It is a fast runner (60 km/hr). A single stride can cover up to 4 m. The bird reaches a height of 2.5 metres. The weight can be upto 120 kg. Wings are nonfunctional. Neck is very long and curved. Beak is short but stout. Foot has two unequal toes with padded under surface. Urinary bladder is present. Ostrich is raised in certain areas for skin and feathers. The eggs-are the largest with the diameter of about 17cm and weight of 1.5 kg. Male has a copulatory organ.
Emu (Dromaius)
It is the second largest bird which reaches a height of more than 1.5 m. Emu is flightless and confined to Australia. Both neck and body are covered by drab-coloured plumage. Feathers have long after-shafts. The bird is herbivorous. It feeds on roots, herbage and fruits. It is good swimmer. Young ones are striped. The stripes disappear in adults.
Cassowary (Casuarius species)
The flightless bird occurs in N.E. Australia and New Guinea. It reaches a height of 1.5 metres. The head is beautifully coloured due to presence of helmet like horny casque. Foot has three toes. Cassowary is nocturnal and frugivorous. Inner toe has a sharp claw for defence.
Kiwi (Apteryx australis)
It is the national bird of New Zealand. The bird is small, flightless with hair-like plumage. The size is 50-70cm. Colour is brownish with black cross bars. Beak is long. There are four toes, three forward and touching the ground. Kiwi lives in borrows at the foot of trees. It is noctural and carnivorous. Power of smell is well-developed.
Impennae
Penguin (Aptenodytes forsteri)
The flightless bird occurs in flocks in the Antarctic region and some islands of South Africa. Wings (fore-limbs) are modified into paddles (fippers). They can also be used for fighting, walking and other functions. Legs are short. Metatarsals are used for standing erect on land. Feathers are small and scale-like. Air sacs are absent. Feet are webbed. Penguins are good swimmers and divers. They feed on fish. Nests are made on rocky islands. -eggs are incubated by males with the help of loose fold of skin present in between the two legs.
Carinatae or Neognathae (Flight Birds)
1. House Sparrow (Passer domesticus).
Male has a black throat and grey crown. The birds feed on seeds, grains and insects.
2. Crow (Corvus splendens).
It prepares crude nests in the regions of tree forkings. A number of birds live on a tree. The colour is black with greyish or sky blue neck. Crow feeds on almost all edibles (omnivorous). It is adept in stealing.
3. Parrot (= Parakeet, Psittacula krameri)
The bird lives in flocks in hollow of trees and crevices. It is green with red bill. The male has pink and black collar. The upper beak is curved and movable. Lower beak is straight and fixed. The bird feeds on fruits, vegetables and other articles. It has good life span and is a good cage bird. Parrot can imitate human speech. However, it can spread fatal chlamydial respiratory disease called psittacosis.
4. Pigeon (Columba livia).
Blue Rock Pigeon is gregarious but monogamous making nests in or around human dwellings. It feeds on grains, seeds, insects and other articles. The wild bird has blue grey body with two dark streaks on wings, a band across tail and multicolour sheen on neck. A number of domesticated varieties occur.
5. Dove (Streptopelia species). It is sign of peace. The colour is light brown and grey. The bird resembles a pigeon and similarly feeds on grains and seeds. Ring Dove or S. decaoto has a black half ring on neck.
6. Cuckoo (Papeeha, Hierococcyx varius).
Ash-grey coloured pigeon sized bird which has brown and white patches on the under side. During summer, it sings 'pee-kahan'.
7. Koel (Eudynamis scolopaceous = Cuckoo, Indian Nightingale). Male has black plumage with greenish bill. Female has brown colour with white spots. During summer or mango season the male sings-'Ku-oo'. Two toes are forwards and two toes backwards. The female lays eggs in the nest of crow for incubation and care.
8. Hoopoe (Hud-hud, Upapa epops). It has zebra-like markings, fan-shaped crest and long bill. It digs out insects from crevices. Hoopoe can fall down when alarmed and looks like rag.
9. Wood Pecker (Branchyptemus bengalensis). It is golden coloured bird with a long bill and crown. Tongue possesses barbs near the tip. Wood Pecker can take out insects from crecvices of the tree.
10. Grey Heron (Ardea cinerea, verno Anjan). It is a large sized bird with long legs, long highly mobile neck and elongated beak. Grey Heron is often found standing motionless in shallow water. It catches fishes and frogs with the help of long beak.
11. Kingfisher (Alcedo). The bird is commonly found near water bodies and sea shore. It produces a characteristic sound while in flight. The beak is quite large. The animal feeds on small fishes, tadpoles and aquatic insects.
12. Flamingo (= Flemingo, Phoenicopterus). It is a wading bird with pink or scarlet plumage, long slender legs, long mobile coiled neck and heavy bent beak. It often remains standing on one leg with head tucked under feathers. Flamingo feeds on tender aquatic vegetation, molluscs and crustaceans. While feeding the beak is kept upside down in water.
13. Weaver Bird (Baya, Ploceus species). It constructs retort shaped nests.
14. Bulbul (Molpaster species). It is of several types with feathery crest. Common colour is brown with black head and crimson patch under the tail.
15. Kite (Periah Kite, Milvus migrans). Large sized, dirty brown coloured bird of prey which is also omnivorous. Its tail is forked. Upper break is curved. Claws are stout. Eye sight is sharp.
16. White Black Vulture (Pseudogyps bengalensis). The vulture is found in small groups. It feeds on carcases. Head and neck are naked.
17. King Vulture (Sarcogyps calvus). Another old world vulture is Neophron.
18. Barn Owl (Tyto alba). Nocturnal.
19. Great Horned Owl (Bubo bubo, verno Ghughu). Large sized, 60 cm long with plumage mottled reddish yellow, brown and grey on the upper side and light with dark stripes on the under side. Two feather tufts occur over the head, giving the bird the name of great horned owl. Legs are also fully feathered.
20. Falcon (Legger Falcon, Falco jugger).
Birds of prey with ash brown dorsal side and whitish ventral side. The size is that of crow. Peregrine Falcon is Falco peregrinus. Eagle belongs to Aquila (=Aqurilla). It has a very keen eye sight, powerful flight, strong curved claws for catching and holding its prey.
21. Pea Cock (Pavo cristatus).
National bird of India. It is polygamous, feeds on reptiles, birds, insects, grains, etc. Male has brilliant bluish colour, a crest and elongated ocellated tail coverts. The female has dull brown colour, a small crest and no tail coverts.
22. Domestic Fowl (Gallus domesticus).
Raised for meat and eggs.Male possesses spur, larger size, more beautiful plumage, larger comb and larger wattles. Female has no spur. The comb and wattles are small.
23. Jungle Fowl (Gallus gallus).
24. Cattle Egret (Bubalcus ibis).
The bird is commonly found on the back of cattle. It is insectivorous, feeds on ectoparasites of cattle, insects and other animals on the ground. It builds nests over tall trees. Beak is long. Legs are long and slender.
25. Duck (Anas).
It can fly, swim or walk. Drake or male is more beautiful. Toes are webbed. Beak has transverse ridges for straining.
26. Great Indian Bustard (Choriotis nigriceps).

Mammalia
Class mammalia is a group of most advanced chordates which are homoiothermal hairy tetrapods having mammary glands in the female for suckling the young ones. They are the most dominant animals. The number of species is 4000. Mammals originated from reptiles like Dimetrodon in triassic, about 200 million years ago. Today they occupy every part of earth - grasslands, forests, deserts, mountains,. polar ice caps, oceans and dark caves. Bats are adapted to fly even in perfect darkness. Whales and a few more mammals are adapted to aquatic life. The largest animals both over land and inside water are mammals.
Characteristics
(i) Females have mammary glands (modified sweat glands) for feeding the young ones.
(ii) The body is covered by epidermal hair.
(iii) The animals are homoiothermal (endothermic) or warm blooded.
(iv)They have two pairs of pentadactyl limbs and are therefore tetrapods.
(v) Heart is four-chambered. It ensures a regular supply of oxygenated blood to all body parts.
Erythrocytes or red blood corpuscles are biconcave and enucleate (oval and flat in Camel and Llama).
(vi) Only left aorta is present. Renal portal system is absent.
(vii) A diaphragm separates thorax from abdomen.
(viii) Skin is glandular. It possesses sweat (sudoriferous) and oil (sebaceous) glands.
(ix) Cervical vertebrae are seven in number with variation of 6 - 9 in Sloth (order edentata), Sea Cow and Manatee (order sirenia). Skull is dicondylic. Vertebrae are acoelous.
(x) External ear contains a fleshy pinna.
(xi) Teeth are thecodont (embedded in sockets), heterodont (different types, four-incisors, canines, premolars and molars) and diphyodont (two sets, milk and permanent).
(xii) Respiratory and digestive tracts are separate due to development of secondary plate. An epiglottis is present over the opening of trachea or larynx. Pie uric cavity is coelomic.
(xiii) Lungs are well developed. Their functioning is enhanced by presence of muscular diaphragm.
(xiv) Urinary bladder is present. Kidneys are metanephric. Mammals are generally ureotelic.
(xv) Optic lobes are converted into corpora quadrigemina. Corpus callosum connects the two cerebral hemispheres. Cranial nerves are 12.
(xvi) In males the testes descend outside the body in scrotal sacs.
(xvii) Fertilization is internal. Mammals are viviparous where the foetus is nourished by the mother through placenta. The eggs are, therefore, small and alecithal. Class mammalia is divisible into three subclasses - prototheria, metatheria and eutheria. The last two are collectively called theria.
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Subclass Prototheria
(i) Primitive mammals which lay eggs.
(ii) Newly hatched animals are nourished on the milk of mother. Teats absent.
(iii) Testes are abdominal.
(iv) Cloacal aperture is present.
(v) Vagina absent in females. Males possess penis but only for insemination.
(vi) Clavicles are separate. An interclavicle is present. It makes the clavicular part T -shaped.
(vii) External pinnae are absent. Living prototherians are also called monotremes as they belong to the order monotremata. Romer has called them unfinished mammals. Examples. Platypus, Spiny Ant Eater.
Platypus (Duck Billed Platypus, Omithorhyncus anatinus)
It is a semi-aquatic prototherian found in Australia and Tasmania. It lives in burrows on the banks of river and streams. Eggs are laid in special nested burrows. The animal has a broad bill or beak, teeth only in the young stage, flat tail, webbed and clawed digits. Females possess mammary glands but teats or nipples are absent. Milk collects in two abdominal grooves from where the young ones obtain the same through lapping. Male has a poisonous spur .on the hind limbs. Platypus feeds on fresh water animals. It swims with the help of webbed feet. and flattened tail.
Spiny Ant Eater (Tachyglossus aculeatus = Echidna aculeata)
It is an insectivorous, burrowing prototherian of Australia, Tasmania and New Guinea. Jaws are prolonged into beak-like muzzle. Teeth absent. Tongue is sticky. The two modifications help in picking up insects. The upper surface bears spines. Hair occurs. Second claw of each hind limb is longer and curved. It is used for cleaning spines and fur. Hence called toilet claw. Male has a grooved poison spur on hind limbs. Milk glands are functional in both sexes. The phenomenon is called gynaecomastism. Female has a pouch or incubatorium during breeding period for incubation of eggs and for keeping the young ones.
Another Spiny Ant Eater is Zaglossus (=Proechidna). It is confined to only New Guinea. Spines are shorter and concealed under long fur. Each limb carries three clawed toes instead of five. 00
Subclass Metatheria
(i) Placenta is simple and small. Young ones are born prematurely.
(ii) Teeth are monophyodont.
(iii) Corpus callosum is absent or rudimentary.
(iv) In male a scrotum develops but in front of the penis.
(v) Two distinct uteri and vaginae occur in females.
(vi) Anal and urinogenital apertures are controlled by a common sphincter.
(vii) The females have a pouch or marsupium for keeping and nourishing the young ones. Mammary glands open into marsupium. Metatherians are also called pouched mammals or marsupials. They constitute the dominant fauna of Australia and nearby islands.
Examples. Kangaroo, Koala, Opossum.
Kangaroo (Macropus major)
It lives in Australia and Tasmania. Kangaroo is the national animal of Australia. The animal is herbivorous and gregarious. There is a small head with pinnae, large body, a long muscular tail, shorter fore limbs with five digits and longer hind limbs with four digits (one free, three fused). Kangaroo can walk on all the four limbs but gallops on hind limbs (saltatorial locomotion). Tail is used in balancing and as a tripod. Young one is born singly in blind, naked and helpless state, hardly 2.5 cm long. It is kept in the ventral pouch of the female till it grows to become independent. Kangaroo has two species, larger grey and smaller reddish.
Koala (Phascolarctus).
American Opossum (Didelphis).
Marsupial Mole (Notoryctus) and Bandicoot (Perameles) are fossorial. Water Opossum(Chironectes) is aquatic. Flying Opossum (Petaurus) is a able to glide (volant).
Subclass Eutheria
(i) It includes placental mammals with well developed placenta for nourishing the foetus.
(ii) Cerebrum has corpus callosum.
(ii) Testes come to lie in scrotal sacs behind the penis.
(iv) Teeth thecodont, diphyodont and heterodont. Young ones are born in advanced stage of formation. The period between fertilization and delivery is called gestation period. It is the shortest in opossums (12-13 days and the longest in Elephant (609 days).
(v) Anus and urinogenital apertures have separate sphincters. Eutheria includes a large number of orders.
Order Insectivora
(i) Primitive placental mammals with abdominal testes
(ii) The members have prolonged snout, sharp teeth (including canines), plantigrade feet with claws. Examples. Mole, Shrew, Hedge Hog.
Mole (Talpa micrura)
It is a black coloured short tailed burrowing animal of 10-12 cm length found in Assam. Eyes are covered by skin. It feeds on worms
Shrew (Musk Shrew, Chachhunder, Crocidura murina)
It is small sized (10 -15 cm long) nocturnal insectivore which has a naked tail, elongated snout, small eyes and ears, dark grey or blackish brown colour and musky odour. The animal produces a shrill cry. It feeds on cockroaches and other insects.
Water Shrew: It is the smallest mammal. Tree Shrew is believed to be remote ancestor of apes/humans.
Hedge Hog (Hemiechinus, Paraechinus species)
It is a nocturnal animal having a globular body, pointed snout, small stumpy tail and short limbs. Except head, throat and belly, the remaining body is covered with erectile spines. Spine colour varies from base to top. Animal can roll up into a ball in time of danger and during day. It feeds on worms, snails and small lizards.
Order Dermoptera
Flying Lemur (Galeopithecus or Cyanocephalus volans). A hairy fold of skin, called patagium, is present on the sides of body to help the animal in gliding. Flying Lemur is arboreal, noctu.rnal and herbivorous. It is found in Malaya and East Indies.
Order Chiroptera
The order includes bats. Fore limbs have elongated digits that support an expanded fold of skin or patagium used for flying. Hind limbs are weak but their digits end in strong claws used for clinging or hanging. Bats have abdominal testes. They feed by night. Eye sight is not much employed. The flying mammals avoid collision by eco-apparatus or radar mechanism.
Small Bat (Flitter Mouse, Scotophilus species)
It is insectivorous, gregarious or solitary with dull brown colour, small snout, prominent pinnae and a long tail which is included in wing or patagium. The first digit of fore limb bears a claw. The animal is active during dusk and dawn. It hangs in secluded places during the day time.
Flying Fox (Pteropus species)
It is large-sized frugivorous bat which also sucks juice and nectar. Pollination is accomplished in the process. Face is fox-like. Eyes are large. Pinnae are small. The colour is reddish or brownish with black wings. Snout is enlarged while tail is absent. Both first and second digits of fore limbs bear claws.
Vampire Bat (Desmodus, Diphylla species)
It is small sized bat found in America. Vampire bats are blood sucking animals.
Order Edentata/Xenartha
Teeth are fewer or absent. The fewer teeth lack roots and enamel. Testes are abdominal. Tongue is long and protrusible. Examples. Armadillo, Sloth, Giant Ant Eater.
Armadillo (Dasypus novemeinctus)
It is american eaentate that is omnivorous, nocturnal and burrowing animal. The body is covered by bony plates with a few joints. Hair occur in between bony plates. Common type 9-banded. Snout is elongated. Only molar teeth are present. Claws are strong. Female produces four to eight young ones of one sex due to breaking of embryo.
Sloth (Three Toed Sloth, Bradypus tridactylus)
The animal has rounded face, long limbs with long curved claws for hanging upside down on the tree branches. The body is covered by long hair. Algae grow over the hair. Sloth is found in America and is omnivorous. Cervical vertebrae are.-nine in Bradypus and six in two toed sloth (Choloepus).
Order Pholidota
Teeth are absent. Tongue is long and protrusible. Limbs have curved claws. Body is covered by horny scales. Examples. Scaly Ant Eater.
Indian Pangolin (Scaly Ant Eater, Manis crassicaudata)
It has an elongated snout, very long (upto 30 cm) sticky tongue, a long horny tail, scales (derivatives of hair) over the body and tail, strong curved claws. It lives in burrows of their own, burrows of other animals, trees and other places in forests. Pangolin breaks open termite and ant nests, and picks up the insects by its long sticky tongue. At the time of danger, it can roll up into a ball. Pangolin may have small stones in its stomach (like gizzard of birds). It is, therefore, also called 'bajra-kit'.
Order Lagomorpha
(i) Upper jaw contains two pairs of incisors while the lower jaw has one pair of them.
(ii) Tail is short.
(iii) Hind limbs are longer and used for leaping.
(iv) Pinnae are large.
(v) Animals gnaw the food like rodents.
(vi) Canines are absent and a diastema occurs.
(vii) Upper lip is cleft in the middle. Examples. Rabbit, Hare.
Rabbit (Oryctolagus cuniculus)
It is a herbivorous, crepuscular (move out in twilight), cursorial (runner with leaps), fossorial (in burrows) and polygamous. It shows coprophagy (eating faecal matter). Size is about 40 cm. Colour is dust brown in wild form but white, black and other pigmentations in the domesticated form. Upper lip has a median cleft through which incisors can be observed. It is called hare lip. Incisors are grooved. Young ones are born naked, deaf and blind.
Hare (Lepas nigricollis)
It has a brown earthly colour with white under-surface. Pinna has black tip. Hare lives a solitary life. The young ones are born with functional eyes and fur.
Order Rodentia
(i) The animals gnaw their food.
(ii) One pair of long sharp chisel-like incisors occur in each jaw.
(iii) Diastema occurs in place of canines. Even some anterior premolars may also be involved in diastema formation.
(iv) Limbs are roughly similar though the hinder may be slightly longer. Examples. Rat, Mouse, Squirrel, Porcupine, Guinea Pig, Beaver.
Rat (Rattus rattus)
It is greyish black on the back and ash-coloured on the under-side. The body is upto 18 cm with the tail reaching upto 20 cm. Snout and pinna tips are hair-less. Vibrissae are present. Tail bears scales along with a few hair. Rat feeds on all types of foods but more so on grains. It is nocturnal but can be active during the day as well. Rat may spread diseases like plague.
Mouse (Mus musculus)
It is smaller than rat (8 cm body, 10 cm tail) with a reddish brown top and light brown under surface.
Guinea Pig (Cavia porcellus)
It is gregarious, low built nocturnal, herbivorous animal of 25 - 30 cm length. Guinea Pig lives in burrows. Body is covered by coarse hair. Head is large. Pinnae are short. Fore-limbs have four digits and hind limbs three digits. Tail is rudimentary. Along with white rat, it is an excellent laboratory animal.
Squirrel (Striped Squirrel, Funambulus pennati)
It is an arboreal animal with three or five longitudinal dark coloured stripes on the back. Tail is long and bushy. The animals feeds on seeds, nuts and fruits (frugivorous). Fore limbs are shorter with four digits. Hind limbs are longer with five digits.
Giant Flying Squirrel (Pentaurista pentaurista)
It has well developed patagia for gliding.
Beaver (Castor fiber)
It is a nocturnal gregarious rodent with webbed toes, sharply clawed digits of fore-limbs, flat tail with scales, thick soft fur all over body and an additional claw over second toe. Beaver builds dams across streams. It is fast swimmer and excellent diver. The animal feeds on bark of trees. The trees are often killed in the process. Beaver is hunted for its flesh, fur and castoreum (from perineal sacs for perfume and medicine).
Porcupine (Hystrix indica)
It is a nocturnal, gregarious, burrowing and herbivorous animal found near water courses. It has erectile long rigid spines (derivatives of hair) on the back for defence. Porcupine produces pig-like grunting cries. It is quite destructive to standing crops, vegetables and fruits.
Order Cetacea
(i) The order has fish-like aquatic mammals with paddle like fore-limbs. Hind limbs are absent. Their vestiges occur in some Greenland whales.
(ii) Teeth are numerous, similar and monophyodont. Those of upper jaw form whale bone in whales.
(iii) A dorsal fin-like structure often present.
(iv) Posterior end bears a flattened tail with two horizontal flukes.
(v) Hair occur only in embryo and snout of the adult
(vi) The skin does not bear any gland. Pinnae are also absent.
(vii) A thick insulating layer of fat or blubber occurs below the skin.
(viii) Milk is squirted down the throat of baby by muscular contraction in mother. Examples. Whale, Dolphin, Porpoise. Blue Whale (Balaenoptera musculus) is the largest living animal with a length of upto 30 - 35 metres and a weight of 135 - 209 metric tannes.
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Whale (Balaenoptera indica)
It is gregarious marine mammal of large size which feeds on small fishes, molluscs, crustaceans etc. including plankton. Whale swims with the help of tail and flippers. It can remain submerged for several minutes. Exhalation sends out a thick cloud of several metres in height. The upper jaw bears a whale bone consisting of two rows of 600 - 800 plates. Whale bone acts as a strainer. Whale is hunted for its blubber.
Dolphin (Platinista gangetica)
Dolphin is a highly intelligent aquatic mammal which can imitate human laughter. It moves in shoals and feeds on arthropods, molluscs and fishes. The body is 2 - 3 metres long with a beak like rostrum having numerous teeth. Pinna is absent. Fore limbs are modified into flippers. Hind limbs are absent. River Dolphin (vern. Susu) of India is found in Ganges and Brahmputra. It also occurs in Pakistan, China and Latin America. New born dolphins possess hair but they are soon shed. The body is brownish in colour.
Indian Porpoise (Delphinus perniger)
It is found in Bay of Bengal. Porpoise is smaller than Dolphin. Colour is black.
Order Carnivora
(i) The mammals of this order have large canines, powerful jaws and claws. Claws are retractile in fast running carnivores. Incisors are small. Premolars and molars are meant mainly for cutting the food. Mastication is little. Flesh is torn by large canines and carnassial teeth (first molars of lower jaw and last premolars of upper jaw).
(ii) Mammae are abdominal. Examples. Dog, Jackal, Wolf, Fox, Mongoose, Otter, Walrus, Seal, Hyaena, Bear, Panda, Cat, Tiger, Lion. The fastest land animal is Cheetah (Acinonyx jubatus) which has become extinct from India. Sea Lion is a large-eared seal.
Lion (Panthera leo)
It is restricted to Gir forest. Length is 2.0-2.5 metres. Colour is pale brown. Tail is tufted at the end. Male possesses mane. Claws are retractile. Feet have thick pads. Lion is carnivorous and polygamous. It is a fast runner which can take a leap of up to 12m.
Tiger (Panthera tigris)
It occurs in almost all forests. Tiger is national mammal of India. Tiger reaches a length of 2.7 - 2.85 m. It has a fawn colour with dark vertical stripes. Claws are retractile. Feet have thick pads. Tail does not possess tuft of hair. Tiger is polygamous and carnivorous. It is fast runner and good swimmer.
Panther (Leopard, Tendua, Panthera pardus)
It is similar to tiger but is shorter (1.5 - 2.0 m). Tail is long. The body is long. The body bears dark spots. Panther can climb trees.
Cat (Felis domestica = F. catus)
It is domesticated carnivore having a number of varieties. Claws are retractile.
Wolf (Canis lupus)
The carnivore has the size of a dog. Legs and abdomen are yellowish while back is grey. It feeds on deer and sheep.
Dog. (Canis familiaris)
It has several varieties. Dog is used for hunting, guarding and criminal detection. Dog can run for long distance. Claws are nonretractile. Dog is omnivorous. Dental formula is i 3/3, c 1/1, pm 4/4, m 2/3.
Hyaena (Lakker Bagha, Crocuta crocuta)
It is .of the size of dog. Hyaena is nocturnal carnivore with a voice similar to crackling human laughter. Common hyaena bears transverse stripes. It has four digits on each limb. Hyaena feeds on carcases but also attacks sheep and poultry.
Jackal (Canis aureus)
Fox (Vulpes bengalensis)
It has a reddish grey body with a pointed snout, large pinnae, bushy tail with a gland at its base that emits its characteristic odour.
Mongoose (Herpestes edwardsi)
It has a low, elongated body of grey colour, long tail and small circular pinnae. Mongoose lives in burrows below bushes and in fields. It feeds on small animals. Its fight with snake is famous. It is, however, not immune to snake venom.
Bear (Himalayan Black Bear, Ursus torquatus)
It has a heavy, clumsy body, thick hair, elongated snout, thick legs with powerful nonretractile claws, poor eye sight but sharp smell and hearing. Bear can climb. It feeds on small animals, fruits and honey. ¬
Otter (Ud-bilau, Lutra lutra)
It is a good swimmer as well as runner with stream-lined body, water proof fur, clawed and webbed digits and thick muscular tail having flattened tapering end. It feeds on fish and other aquatic animals.
Walrus (Odobenus rosmarus)
It is marine carnivorous mammal of cold areas where the upper canines are prolonged into tusks for digging food and help in wriggling over land. Fore-limbs are modified for swimming. Hind limbs are also useful for swimming but on shore they can be turned forward for wriggling.
Seal (Phoca vitulina)
It is a marine carnivorous mammal of colder areas which comes to the shore for rest and breeding. Blubber is present. Limbs are paddle-like with webbed digits. Hind limbs are backwardly directed. Tail is short. Nostrils contain valves. Nipples and genitalia are covered by skin folds.
Sirenia (Sea Cow, Manatee)
It is an order of aquatic herbivorous mammals where hind limbs are absent, fore limbs are paddle-like, tail has horizontal fin, pinnae absent, hair few and the males possess tusks, e.g., Helicore (Dugong), Rhytina, Manatus (Manatee). Cervical vertebrae are 6 in Manatee.
Order Proboscidea
The order includes elephants which are the largest land animals reaching a height of 3.0 - 3.45 metres and weight of 5 - 7 tonnes. Nose and upper lip are jointly prolonged to form prehensile proboscis (popularly called trunk). It contains nasal passages. Proboscis is not supported by bones. External nares are present at its tip. Upper incisors are enlarged to form tusks. They are rudimentary in females and long in males. Canines and premolars are absent. Molars are functional. Skin is thick and loose with scanty hair. Limbs are pillar-like, not bending during walking. Digits are short and thick. They are embedded in a common integument and end in nail-like hoofs. Animals are digitigrade. Testes are abdominal. Females possess a single pair of thoracic teats. Elephants are gregarious and herbivorous. An elephant picks up food and water by its proboscis and transfer the same into mouth. Indian Elephant is Elephas indicus (= E. maximus) while African Elephant is Loxodonta africana (Elephas africana). In Indian Elephant the pinnae are relatively shorter, tusks long in male but do not grow beyond lips in female, forehead dome-shaped with a cleft and arched back. African Elephant has larger pinnae, tusks in both sexes, forehead is low flat without a cleft. Back is depressed. Elephants are hunted for their tusks (a source of ivory). They can be tamed and used for carrying heavy weights.
Digitigrade. Walking or running with only the digits touching the ground, e.g., Rabbit, Elephant.
Unguligrade. Running or walking on the tips of digits. Heels raised above the ground level, e.g., Cow, Deer, Horse, Ass.
Plantigrade (Palmigrade). Walking or running with whole sole of the foot touching the ground, e.g., Bear, Human being are plantigrade while walking but become digitigrade while running.
Locomotion. Climbing-Scansorial. Flying- Volant. Running-Cursorial.
Jumping/Leaping/Galloping - Saltatorial.
Order Perissodactyla
It includes unguligrade hoofed mammals with odd number of toes. Canines are reduced or absent. Premolars and molars are similar. Gall bladder, ruminant stomach and true horns are absent. Examples. Horse, Ass, Zebra, Tapir, Rhino.
Horse (Equus caballus)
Completely domesticated with shorter ears, broader hoofs and tail completely covered by long hair. Ass (Equus asinus, E. mager, E. vulgaris)
It is shorter than horse with comparatively larger head and pinnae, narrow hoofs and tail having hair mostly on the lower part. Mule is sturdy sterile hybrid between male ass and mare and stallion. Hinny is hybrid between female ass
Zebra (Equus zebra)
It is similar to ass. The body is black coloured with yellow stripes. Stripe pattern is different in each animal.
Tapir (Tapirus terrestris)
It has a short proboscis formed of nose and upper lip. The animal is nocturnal, herbivorous and found in American and East Asian forests. The fore-limbs have four digits while the hind limbs have three digits.
Rhino (Rhinoceros unicornis = R. indicus)
It occurs in Nepal and eastern parts of India. Rhino is a large animal having a hairless, folded and very thick skin resembling armour. The animal is herbivorous. Legs are comparatively short with three functional digits having broad hoofs. Tail is comparatively narrow. Hair occur over pinnae and tip of tail. Indian Rhino possesses one keratin horn over the snout. There are two such horns in African Rhino. Horn is formed by a bundle of fused hair. It has no connection with skull. Rhino is hunted for its horn.
Order Artiodactyla
(i) It includes even toed unguligrade mammals, generally with hoofs.
(ii) True horns occur in some I forms.
(iii) Stomach can be ruminant or nonruminant. Ruminants have the habit of chewing the cud.
Nonruminants include Pig and Hippopotamus. Stomach of Camel and Llama has three chambers: (rumen, reticulum and abomasum). The first two chambers have pouches. In true ruminants the stomach is four chambered (rumen, reticulum, omasum and abomasum), e.g., Deer, Giraffe, Buffalo, Cow, Sheep, Goat, Antelope.
Hippopotamus (Hippopotamus amphibius)
It, is the second bulkiest land animal. Hippopotamus lives most of the time in water (lakes, rivers, swamps; hence riverine horse). It is nocturnal, gregarious and herbivorous. Its skin is nearly naked but thick and warty. Sweat is reddish. Head is large with broad snout. Tail is short and compressed laterally. Limbs are comparatively short with four partially webbed digits.
Cow (Bos indicus) and Buffalo (Bos bubalus) are domesticated mammals that provide us with milk. They have hollow horns. Two hoofed digits are functional.
Sheep (Ovis) and Goat (Capra) resemble Cow and Buffalo in having horns and two functional digits. They yield comparatively less quantity of milk. The animals are slaughtered for meat. Sheep provide wool. Dental formula of sheep of i 0/3, c 0/1, pm 3/3, m 3/3.
Pig (Sus scrofa) is domesticated. Wild Pig or Boar (Sus cristatus) occurs in jungles. It is brownish black animal with coarse, hair, a long muzzle with movable snout, upper canines curved and forming tusks, tufted tail, shorter limbs with four digits but only two reaching ground. Boar is nocturnal and gregarious. It is scavenger as well as omnivorous. Stomach is nonruminant.
Deer (Cervus species)
Deer are gregarious, ruminant herbivores where the male or stag bears solid bony horns called antlers. Antlers are commonly branched and shed once a year. The hind or female deer mayor may not have horns. Deer are fast runners. They have four digits in each limb but only two reach the ground. Deer are of several types-Chitalor Spotted Deer (Cervus axis), Swamp Deer (Barasingha, Cervus duvaucelli), Hog Deer (Para), Sambar, Barking Deer, Musk Deer, etc. Musk Deer (Moschus moschiferus) is without antlers but the upper canines are ever growing. Male Musk Deer has a musk bag or gland from which musk (kasturi) is squeezed.
Camel (Arabian Camel- Camelus dromedarius, Turkish Camel- Camelus bacterianus)Camel is a hornless large sized domesticated even toed mammal which has three chambered stoma.ch, nails instead of hoofs, pads or cushions on under surface of feet, oval flat erythrocytes, long neck, long legs, light brown colour, cleft upper lip and one (Arabian Camel) or two (Turkish Camel) humps. Hump is rich in fat. Eyes and nostrils possess heavy fringes of hair to protect them from sand. Camel produces very little urine. It can also drink large quantity of water. The cells can tolerate dehydration upto 40%. This helps the camel to function as ship of desert and remain without water for 10-15 days. (Water .pockets attached to stomach are actually food storing chambers). During dehydration, water is removed from blood and not from individual cells.
Giraffe (Giraffa camelopardalis)
It is the tallest mammal (5.48-6.1 metres) with long neck, erect mane, long limbs (anterior ones taller) two-hoofed digits, delicate head with protruded snout and a pair of bony horns covered with skin. Tail is tufted. Giraffe occurs in Africa. It browses on trees. Fore limbs and hind limbs of one side move together while walking.
Order Primata (Primates)
Primates have evolved from tree shrews. They are the most advanced of all mammals. The animals are intelligent mammals with convoluted cerebral hemispheres, ventral foramen magnum, five digits with nails, grasping hands and feet, forwardly directed eyes with binocular vision and a pair of thoracic teats or mammae in females. Primates are plantigrade. There are two types of primates, prosimians, (before monkey) and simians (monkeys). Prosimians have claws in some of their digits. Others have nails. Eyes are large with colour vision. Hands and feet are of grasping type. Hind limbs are generally longer. Tail mayor may not be present. Prosimians include lemur, loris and tarsier. Simians have nails on all the digits. Face is flat with muscles for emotional expression. Fore-limbs are longer (exception humans). Pollex and hallux are opposable (except in human hallux). Brain is larger. Simians include monkey, apes and human.
Lemurs
They are restricted to the island of Madagascar. Ten genera of living lemurs occur there. Lemur is diurnal. It occurs in troops dominated by females. Snout is long. Upper lip is cleft. Rhinarium or philtrum is moist. Eyes somewhat lateral. External ears are often large. Pollex and hallux take part in grasping. Digits have nails but the second toe has toilet claw. Fur is thick. Vibrissae are present. Dental formula is 2+1+3+3 X 2. 2+1+3+3
Lower incisors and canines form dental comb for grooming and feeding.
Indian Loris (Nyctecebus bengalensis)
It is an arboreal, crepuscular or nocturnal prosimian with long nonprehensile tail that feeds on fruits, leaves, flowers, eggs and small animals. The eyes are slightly lateral with poor vision. Claw occurs on the second toe. All other digits possess nails.
Slender Loris (Loris tardigradus)
It is tail-less, slow moving endangered nocturnal prosimian of South India and Sri Lanka. It has large forward eyes, pointed muzzle and thin round ears. Loris is omnivorous.
Tarsier (Tarsius spectrum)
The tarsal region of the feet is elongated. Second and third toes bear claws. Eyes are large, protruding and forward. Pinnae are large. Neck can be turned to move the face backwardly. Tail is long. Tarsier is arboreal, nocturnal and carnivorous.
Rhesus Monkey (Macaca mulatta)
It is common monkey that is arboreal as well terrestrial, omnivorous and gregarious. Body is yellowish brown. Head is rounded. Face is red. Cheek pouches are present. Buttocks possess thick pads called ischial callosities. Digits bear nails. Hands and feet are of grasping type. Tail is present but is not prehensile.
Baboon (Langur, Semnopithecus = Presbytis entellus)
Baboon is a terrestrial as well as arboreal, gregarious and herbivorous primate which can leap a distance of 6-9 metres. Face, pinnae, hands and feet are black. Body is greyish. Cheek pouches are absent. Head is rounded. Eye brows possess long stiff hair. Ischial callosities occur. Tail is very long. It is slightly prehensile.
. New World Monkey (Cebus capucinus, Ateles/Spider Monkey)
The monkey lacks ischial callosities and cheek pouches. Tail is prehensile. Nostrils are forwards. Nose is flat and has a broad internasal septum. Hair of the head form a hood-like configuration.
Apes (Family Pongidae)
Apes are man-like primates. They are without tails. Fore-limbs are longer than hind limbs. Fore limbs are used for locomotion or jumping on trees. The phenomenon is called brachiation. They can walk in a semi-erect position on the outer edges of feet and knuckles. Cheek pouches and ischial callosities are absent. Brain is large and shows convolutions. There are four types of apes - Gibbon, Orang-Utan, Gorilla and Chimpanzee. The only ape found in India is Gibbon.
Gibbon (Hylobates hoolock)
It is the smallest ape found in eastern Himalayas and South-East Asia. Gibbon can walk almost erect. Height is one metre. In the erect position the fore-limbs can touch the ground. Hind limbs are shorter. Males are black coloured while the females are slightly brownish. Eye brows are white. Two hard ischial callosities are present which are absent in other apes. Gibbon is arboreal and omnivorous but more commonly frugivorous. It can jump to a distance of 6 -12 metres.
Orang-Utan (Simia/Pongo pygmaeus)
It is a herbivorous (frugivorous) ape found in Borneo and Sumatra forests of Indonesia. The ape builds a sort of resting place on trees. OrangoUtan has a face similar to that of human. Body length is 1.2 -1.5 metres, while the fore-limbs are 2.0 metres long. Belly is heavy. Pollex and hallux are short. The body is covered by long sparse brown hair.
Gorilla (Gorilla gorilla)
Gorilla is the largest ape with a height of 2. 0 metres and weight of 250 kg. It is found in Africa. Gorilla lives on trees as well as on ground. It has a black colour, prominent jaws, canines and brow ridges. A chin is absent. Gorilla is herbivorol1s but can be very ferocious and dangerous.
Chimpanzee (Pan = Anthropithecus satyrus)
It is the most intelligent of the apes found in Africa. Chimpanzee reaches a length of 1.5 metres, and a weight of 80 kg. It contains a chin. Prominent brow ridges occur. Ears and lips are large. The animal is herbivorous but can also eat insects. Chimpanzee can be named and trained.
Human (Homo sapiens, family Homonidae)
Human or mammal with a language is the most advanced of all animals, though not in physique. Homo sapiens is a terrestrial social animal with perfect bipedal locomotion except during infancy. Cerebrum is large and convoluted. Tail is absent. Brow ridges are ill-developed but chin is prominent. Head is round. Fore-head is broad. Face is almost flat. Eyes are forward. Arms are shorter than legs. Hands are of grasping type due to the presence of opposable thumb. In feet, the great toe does not work against other toes. Digits bear nails. Females have a single pair of thoracic mammae. A beard is present in males. Hair are sparse on the body but on the head they are long and ever growing. Humans dominate the world due to their ability to speak, logical thinking, memory and opposable thumb capable of fabricating and use of tools.
00

1. What are the difficulties that you would face in classification of animals,if common fundamental features are not taken into account?
2. If you are given a specimen what are the steps that would follow to classify it?
3. How useful is the study of the nature of body cavity and coelom in the classification of animals?
4. Distinguish between intracellular and extracellular digestion?
5. What is the difference between direct and indirect development?
6. What are the peculiar features that you find in parasitic platyhelminthes?
7. What are the reasons that you can think of for the Arthropods to constitute the largest group of the animal kingdom?
8. Water vascular system is the characteristic of which group of the following:
(a) Porifera
(b) Ctenophora
(c) Echinodermata
(d) Chordata
9. “All vertebrates are chordates but all chordates or not vertebrates” Justify the statement.
10. How important is the presence of air bladder in Pisces?
11. What are the modifications that are observed in birds that help them fly?
12.Could the number of eggs or young ones produced by an oviparous and Viviparous mother be equal why
13. Segmentation in the body is first observed in which of the following:
(a) Platyhelminthes
(b) Aschelminthes
(c) Annelida
(d) Arthropoda

14. Match the following:

00 Assignment (Fill in the blanks)
Fill in the blanks: 1. Over a ┅species of animals have been described till now.
2. Write any five Fundamental features common to various individuals ┅, ┅, ┅, ┅, and ┅. 3. Sponges exhibit ┅level of organization. br> 4. In coelenterates the cells performing the same function are arranged into tissues, hence is called ┅ level of organization.
5. ┅.is a mesodermally derived rod-like structure.
6. Animals with ┅ are called chordates.
7. The phyla of non chordates are e.g., porifera to echinoderms. These include Porifera┅, ┅, ┅, ┅, ┅, ┅, ┅ and ┅.
8. Members of phylum ┅are commonly known as sponges.
9. Sponges have a water transport or canal system. Water enters through minute pores called ┅ which are present in the body wall.
From a central cavity called spongocoel, water goes out through the ┅.
10. ┅or collar cells line the spongocoel and the canals in sponges. The is skeleton made up of ┅or sponging fibres.
11. ┅. (Scypha), ┅ (Fresh water sponge) and ┅ (Bath sponge) are examples of sponges.
12. The name cnidaria is derived from the ┅ or ┅present on the tentacles and the body.
13. ┅or ┅ contain the stinging capsules or nematocytes.
14. ┅are used for anchorage, defense and for the capture of prey.
15. Cnidarians exhibit tissue level of organisation and are ┅blastic.
16. Cnidarians have a central gastro-vascular cavity with a single opening, ┅
17. Corals have a skeleton composed of ┅
18. Cnidarians exhibit two basic body forms called┅and ┅
19. The ┅is a sessile and cylindrical form like Hydra, Adamsia, etc.
20. The ┅s umbrella-shaped and free-swimming like Aurelia or jelly fish.
21. Alternation of generation in cnidarians is called┅
22. The examples of cnidarians are ┅ (Portuguese man-of-war), ┅ (Sea anemone), ┅ (Sea-pen), ┅ (Sea-fan) and ┅ (Brain coral).
23. Ctenophores are commonly known as sea ┅or comb ┅
24. Write three characters of Ctenophores ┅, ┅. and ┅
25. The body of Ctenophores bears ┅external rows of┅comb plates, which help in ┅
26. Digestion is both ┅
27. ┅ (the property of a living organism to emit light) is well-marked in ctenophores.
28. ┅ and ┅ are examples of Ctenophora.
29. ┅have dorso-ventrally flattened body, hence are called flatworms.
30. These are mostly endoparasites found in ┅ including human beings.
31. Flatworms are ┅ symmetrical, ┅blastic and┅lomate animals with organ level of organisation.
32. Hooks and suckers are present in the parasitic forms of ┅
33. Specialised cells called ┅ cells are present in help in Platyhelminthes for osmoregulation and excretion.
Top

1. Classify Kingdom Animalia upto phylum.

2. Classify phylum Vertebrata upto classes.

3. Classify Phylum Porifera, also give suitable examples.

4. Classify Phylum Coelentrata( Cnidaria) , also give suitable examples.

5. Classify Phylum Platyhelminthes, also give suitable examples.

6. Classify Phylum Aschelminthes, also give suitable examples.

7. Classify Phylum Annelida, also give suitable examples.

8. Classify Phylum Arhropoda, also give suitable examples.

9. Classify Phylum Mollusca, also give s suitable examples.
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24 Apr 2023
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1. Write name of various phyla of kingdom Animalia. 2. Which are subphyla of phylum chordata. 3. Write various classes of Vertebrata