ANIMAL KINGDOM. Levels of Organization:-

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1 4 ANIMAL KINGDOM Terminologies Related to Animal Classification :- Metazoa :- Animal groups are characterized by mobility and the presence of a sensory or a nervous system. These sys-tems receive stimuli from the environment and ani-mals respond by exhibiting some behavior. The only exception is of poriferans (pore-bearers) or the sponges. They have no cell that can be termed as nerve cell. Like plant life, early animal life also arose in sea. The animals which live on the sea floor are called ben-thonic (e.g., echinoderms, corals, and deep sea fishes), whereas those which swim about actively in sea are called nektons. The multicellular eukaryotic organisms with holozoic mode of nutrition are called metazoans. Based on the complexity of organization, metazoans are further sub-divided into two subkingdoms, Parazoa and Eumetazoa. Parazoa : Parazoa include the sponges in which cells are loosely aggregated and do not form tissues or organs. Eumetazoa : Eumetazoa include the rest of animals in which cells are organized into structural and functional units called tissues, organs, and organ systems. Levels of Organization:- 1. Cellular level :- Though all members of Animalia are multicellu-lar, all of them do not exhibit the same pattern of cell organization. For example, in sponges, the cells are arranged as loose cell aggregates, i.e., they exhibit cellular level of organization. Some division of labor (activities) occurs among the cells. 2. Tissue level :- In coelenterates and ctenophores, the arrangement of cells is more complex. Here, the cells performing the same function are arranged into tissues. Hence, it is called tissue level of organization. 3. Organ level :- A still higher level of organization, i.e., organ level is exhibited by the members of Platyhelminthes and other higher phyla where tissues are grouped together to form organs, each specialized for a particular function. 57

2 In animals such as annelids, arthropods, molluscs, echinoderms, and chordates, organs have asso-ciated to form functional systems, each system concerned with a specific physiological function. This pattern is called organ system level of or-ganization. Organ systems in different groups of animals exhibit various patterns of complexities. For example, the digestive system in Platyhel-minthes 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: open type and closed type. Different types of body symmetry Open type :- In this type of circulatory system, the blood is pumped out of the heart and the cells and tissues are directly bathed in it. The blood is pumped by the heart into the blood vessels that open into blood spaces (sinuses). There is no capillary system (e.g., in most arthropods, non-cephalopod molluscs and tu-nicates). These sinuses are actually the body cavities and are called hemocoel. The pressure of the blood is low; it moves slowly between the tissues and, finally, re-turns to the heart via open-ended blood ves-sel. Closed type :- Many invertebrates and all the vertebrates, including humans, have a closed circulatory system. In closed type, the blood flows inside the body through a series of blood vessels of varying diameter (arteries, veins, and capil-laries). In this system, the same blood regularly cir-culates in the body under high pressure and returns back to the heart without leaving the system of tubes. Symmetry :- Based on the basis of their body symmetry, animals can be cat-egorized as follows: Radial symmetry : When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry (Fig. 4.1a). The animals with radial symmetry are put in the group Radiata, e.g., cnidarians (hydra and jelly fish). Biradial symmetry is present in sea anemone, ctenophores. 58

3 Bilateral symmetry : The animalswith bilateral symmetry are put in the group Bilateria. The body can be divided into identical right and left halves in only one plane (Fig. 4.1b). For example, platyhelminthes, annelids,arthropods, etc. (platyhel-minthes to chordates). Asymmetry : Asymmetric organisms cannot be divided along any plane to produce two equivalent halves. Sponges are mostly asymmetrical. Germ Layers :- Germ layers give rise to all the tissues/organs of a fully formed individual. On the basis of the number of germ layers, animals can be diploblastic or triploblastic. Diploblastic : In diploblastic animals, the body cells are ar-ranged in two layers an outer ectoderm and an inner endo-derm with an intervening undifferentiated mesoglea, e.g., coelenterates. Triploblastic : The body wall in animals is made of three germ layers, i.e., ectoderm, mesoderm, and endoderm, e.g., platyhel-minthes to chordates. Germinal layers : (a) diploblastic and (b) triploblastic Body Plan :- Though diverse in shape and size, animals have body that fits in one of the three basic plans: Cell aggregate : Cell aggregate type of body plan is present in sponges. They are clusters of cells with a rudimentary division of labor among them. There are no tissues or organs. Blind sac : Blind sac type of body plan is present in Platyhel-minthes and Coelenterata where the alimentary canal has only one opening. Tube within tube : Tube-within-tube type of body plan is pre-sent in Nemathelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, and Chordata. The digestive system is a con-tinuous tube with an opening at both ends. 59

4 Body Cavity or Coelom :- The presence or absence of cavity between the body wall and gut wall is very important for classification. Eucoelomates : True coelom is a body cavity which arises as a cavity in embryonic mesoderm. In this case, the mesoderm of the embryo provides a cellular lining, called coelomic epi-theliumor peritoneum, to the cavity. The coelom is filled with coelomic fluid secreted by the peritoneum. True coelom is found in annelids, echinoderms, and chordates. True coelom is of two types: 1. Schizocoelom : It develops by the splitting up of meso-derm. It is found in annelids, arthropods, and molluscs. The body cavity of arthropods and non-cephalopod molluscs is called hemocoel. 2. Enterocoelom : The mesoderm arises from the wall of the embryonic gout or enteron as hollow outgrowths or enterocoelomic pouches. It occurs in echinoderms and chordates.pseudocoelomates:the body cavity is not completely lined with mesoderm. Instead, the mesoderm is present as scattered pouches in between the ectoderm and endoderm (Fig. 4.3b). Such a body cavity is called pseudocoelom, e.g., in round-worms. Acoelomates : The animals in which the coelom is absent are called acoelomates, e.g., poriferans, coelenterates, ctenophores, and flatworms. In flatworms, the spaces between various organs are filled with special tissue called parenchyma Coelomic body cavity : (a) coelom, (b) pseudocoelom and (c) acoelom 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 a pattern called metameric segmentation and the phenomenon is known as metamerism. Metameric segmentation is present in annelids only. Notochord :- Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some ani-mals. Animals with notochord are called chordates and animals which do not have this structure are called non-chordates, e.g., porifera to echinoderms. 60

5 Phylum Protozoa (Unicellular Protists) :- There are about 15,000 species of protozoans known to exist in the world. They are microscopic heterotrophic organisms in which a single cell performs all the vital activities. For this reason, protozoans are also referred to as acellular organisms. They are aquatic (fresh water and marine) and cosmo-politan in distribution. Some forms are predators and some parasitic. The protozoan cell body is either naked, for example, Amoeba, or surrounded by a non-rigid pellicle. Cel-lulose is absent in pellicle. Some protozoans secrete shells of various inorganic compounds as external covers (foraminiferans). Different types of locomotory structures are found in protozoans. They may bear flagella (flagellates), cilia (ciliates), or pseudopodia (sarcodines). Locomotory structures are absent in the parasitic forms (sporozoa). In protozoans, neurofibrils and contractile myofibrils are present underneath the cell surface. Most protozo-ans are free-living and aquatic. They are holozoic and feed largely on bacteria, micro-scopic algae, and minute animals such as rotifers or on other protozoans including members of their own species. Some protozoans are holophytic; they contain chlo-rophyll and prepare their own food by photosynthe-sis (e.g., Euglena, Amoeba, Paramecium, Elphidium). The parasitic protozoans feed on materials obtained from the hosts (e.g., Monocystis, Entamoeba, Plasmodium, Trypanosoma, Giardia, etc.). Euglena Contractile vacuole is found in almost all fresh-water protozoans for the maintenance of osmotic concen-tration of cell body. This phenomenon is known as osmoregulation. Contractile vacuole also helps in ex-cretion. Many sporozoan parasites are relatively harmless, but some are harmful also. For instance, Plasmodium vivax and Plasmodium falciparum cause malaria in humans. Protozoans are generally uninucleate, but all ciliates and many amoeboid types are multinucleate. The pattern of reproduction is also specialized in dif-ferent protozoans. Most sarcodines, flagellates, and ciliates show asexual reproduction by binary fission, multiple fission, or even budding. 61

6 Some ciliates, for example, Paramecium reproduces by sexual means in which two individuals come close to each other and interchange genetic information by a process known as conjugation. There is no gamete formation in such a process. In sporozoa, some stages of life cycle show formation of gametes, which are morphologically distinct. Classification of Phylum :- Protozoa Phylum protozoa is divided into four groups: Rhizopoda or Sar-codina, Mastigophora or Flagellata, Sporozoa, and Ciliata. Group 1 : Rhizopoda or Sarcodina :- The locomotion is by pseudopodia; body shape changeable, e.g., Amoeba (free-living), Entamoeba (parasitic or commen-sal), etc. Four types of pseudopodia are: lobopodia (Amoeba), filopodia (Euglypha), reticulopodia (Globigerina), and axopo-dia (Actinophrys sol). Group 2 : Mastigophora or Flagellata :- The locomotion by one or more thread-like flagella. They are free living or parasitic. For example, Euglena : Connecting link between plants and animals Trypanosoma : Parasite causing sleeping sickness Leishmania : Parasite causing kala-azar Giardia : Parasite causing diarrhea Trichomonas : Parasite causing vaginitis in human fe-mals Trichonympha : Symbiont found in gut of termite help-ing in cellulose digestion Proterospongia : Colonial with collar cells, a connecting link between Protozoa and Porifera Two types of flagellates are phytomastigina (with chlo-roplast, plant-like, e.g., Euglena, Chlamydomonas, etc.) and zoomastigina (without chloroplast, animal-like, e.g., Trypanosoma, Leishmania, etc.). Group III : Sporozoa :- All parasites have spore-like stage, no special locomotory orga-nelles, no contractile vacuole (associated with parasitism), and complex life history. For example, Plasmodium : Causes malaria, spreaded by female Anopheles Monocystic : Parasite in the seminal vesicles of earthworm Eimeria : Causes coccidiosis in rabbit and chicken Babesia : Causes hemoglobinuric fever/tick fe-ver in cattle Babesiais a protozoan parasite spread by ticks. In Inida, tick fever is caused mainly by Babesis bigemina. The par-asite enters into red blood cells (RBCs) and destroys them. Group IV: Ciliata :- Locomotory organelles are cilia; nuclei two or more in number. Examples are: Paramecium : Free-living, slippery animalcule Balantidium : Causes balantidial dysentery in man Nyctotherus : Rectal ciliate and endocommensal in frog 62

7 PHYLUM PORIFERA : Also called sponges. Are usually marine and asymmetrical. Have cellular level of organization. Food gathering, respiratory exchange and removal of wastes occur through water canal system. Digestion intracellular. Ostia (minute pores on body), spongocoel (body cavity) and osculum help in water transport. They are lined by choanocytes (collar cells). Body wall has spicules and spongin fibers. Animals are hermaphrodite. Fertilization internal. Development is indirect, with larval stage which metamorphoses to adult. e.g., Sycon, Euspongia. Examples for Porifera : (a) Sycon (b) Euspongia (c) Spongilla PHYLUM COELENTERATA: Also called Cnidarians. Are usually marine and radially symmetrical. Sessile or free-swimming. Have tissue level of organization Diploblastic. Presence of cnidoblast, for anchorage, defense and capture of prey. Central body cavity called gastro-vascular cavity or coelenterone. Digestion extracellular and intracellular. Blind sac type body plan, with one opening called hypostome. Body wall composed of calcium carbonate. Exhibit two body forms: polyp and medusa e.g., Hydra, Aurelia. Alternation of generation between body forms called Metagenesis occurs in Obelia where Medusa sexually reproduced and polyp asexually reproduced. e.g., Physalia, Adamsia. 63

8 Examples of Coelenterata indicating outline of their body form : (a) Aurelia (Medusa) (b) Adamsia (Polyp) Diagrammatic view of Cnidoblast PHYLUM CTENOPHORA : Also called as sea walnuts or comb jellies. Are exclusively marine, radially symmetrical. Have tissue level organisation, are diploblastic. Digestion both extra and intracellular. Body has eight external rows of ciliated comb plates for locomotion. Show Bioluminescence (living organism emit light). Example of Ctenophora (Pleurobrachia) 64

9 Sexes are not separate i.e. hermaphrodite. Reproduce only by sexual methods. External fertilization. Indirect development e.g., Ctenoplana. Pleurobranchia. PHYLUM PLATYHELMINTHES : Also called as flat worms. Have dorsoventrally flattened body. Mostly endoparasites in animals including human. Bilaterally symmetrical, Triploblastic Acoelomate Organ level organization. Absorb nutrients through body surface. Parasite forms have hooks and suckers. Flame cells help in osmoregulation and excretion. Fertilization internal. Many larval stages. Planaria has high regeneration capacity. e.g., Taenia, Fasciola. PHYLUM ASCHELMINTHES : Also called round worms. May be free living, parasitic, aquatic or terrestrial. Are bilaterally symmetrical, triploblastic, Pseudocoelomates. Alimentary canal complete (has muscular pharynx), wastes removed through excretory pore. Organ system level of organization. Sexes separate i.e. dioecious. Shows sexual dimorphism. Females longer than males. Fertilisation internal. Development direct or indirect. e.g., Ascaris, Wuchereria. Examples of Platyhelminthes : (a) Tape worm (b) Liver fluke Aschelminthes Roundworm 65

10 PHYLUM ANNELIDA : Are aquatic or terrestrial, free-living or parasitic. Are bilaterally symmetrical, triploblastic, Organ-system level of organization Metamerically segmented body. Have longitudinal and circular muscles in body wall for locomotion. Aquatic annelid like Nereis has oar shaped parapodia for movement. Have nephridia for osmoregulation and excretion. Nervous system consists of paired ganglia connected by lateral nerves to a double ventral nerve cord. Circulatory system is closed type. Earthworm (Pheretima) and Leech (Hirudinaria) which are hermaphrodites (i.e., monoecious). Nereis an aquatic form is dioecious. Fertilization is external Development is direct or indirect. Examples of Annelida : (a) Nereis (b) Hirudinaria PHYLUM ARTHROPODA : Largest phylum of Animalia includes insects. Are bilaterally symmetrical, triploblastic and organ system level of organization, coelomate and segmented body. Body divisible into head, thorax, abdomen. Body covered by a chitinous exoskeleton. They have jointed appendages. Respiration by gills, book gills, lungs or tracheal system. Circulation is open type. Excretion through malpighian tubules. Sensory organs: Antennae, eyes; Organs of balance: Statocysts. Mostly dioecious. Fertilisation internal. Are mostly oviparous. Development is indirect or direct. e.g., Apis, Bombyx, Anopheles, Locusta, Limulus. Examples of Arthropoda : (a) Locust (b) Butterfly (c) Scorpion (d) Prawn 66

11 PHYLUM MOLLUSCA : Second largest phylum of Animalia. Terrestrial or aquatic. Are bilaterally symmetrical, triploblastic and organ system level of organization, coelomate. Body divisible into head, muscular foot and visceral hump and is covered by a soft and spongy layer of skin called mantle. Unsegmented body. Body is covered by calcareous shell. Respiration and excretion by feather like gills (ctenedium) in mantle cavity. Head has sensory tentacles. Radula-file like rasping organ for feeding. Usually dioecious, dioecious, have indirect development. e.g., Pila, Pinctada, Octopus. Examples of Mollusca : (a) Pila (b) Octopus PHYLUM ECHINODERMATA : Are spiny bodied organisms. Endoskeleton of calcareous ossicles. Are exclusively marine. Radially symmetrical in adult but bilaterally symmetrical in larval stage. Organ system level of organization. Triploblastic and eucoelomate. Digestive system complete. Mouth ventral, Anus on dorsal side. Food gathering, respiration, locomotion carried out by water vascular system. Excretory system is absent. Dioecious i.e. sexes are separate. Fertilization external. Development indirect (free swimming larva) 67

12 Examples for Echinodermata : (a) Asterias (b) Ophiura Phlum Hemichordata/Stomochordata :- Hemichordata was earlier considered as a sub-phylum under chordata. But now it is placed as a separate phylum under non-chordata. The phylum consists of a small group of worms-like marine animals with organ system level of organization. Its character-istics are: In hemichordata or stomochordata, true notochord is absent. Gill slits are present but they are dorso lateral in position. They are worm like, bilaterally symmetri-cal, Triploblastic, and entero-coelomate animals. Stomochord is a hollow outgrowth arising from the roof of the buccal cavity, also called buccal diverticulum. It is present in the proboscis. Dorsal heart, ventral hollow nerve cord, and no res-piratory pigments. Circulatory system is open. Respi-ration occurs by gills. Development is mostly indirect through a free-swim-ming tornaria larva, e.g.,balanoglossus (acorn, tongue worm), Glossobalanus. Sexes are separate. Fertilization is external. Balanoglossus Excretory organ is proboscis gland. Believed to be a connecting link between non-chor-dates and chordates. The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk. Due to the absence of true notochord in hemichordata, many taxonomists do not consider these animals as chordates. Examples: Balanoglossus,Saccoglossus 68

13 Phlum Chorrdata :- The most important characteristics of phylum Chordata are: Post anal tail. Closed circulatory system. Dorsal hollow nerve cord. Paired gill slits on the lateral sides of pharynx. They possess a notochord either throughout life or dur-ing early embryonic development. Chordata Characteristics Sub-Phylum Protochordata or Acraniata :- Sub-Phylum 1: Urochordata :- The larva (Ascidian tadpole) undergoes retrogressive metamorphosis, i.e., change from better developed larva to less developed adult, e.g., Herdmania(sea squirt). This sub-phylum is also called Tunicata because the adult body is enclosed within a leathery test or tunic formed of a cellulose-like organic substance termed tunicin. Vanadocytes are present except in Herdmania. Vanadium gives green color to blood. Excretion occurs by neural gland, hence excretion is glandular. They are exclusively marine. Examples: Salpa, Doliolum, Ascidia. 69

14 Phylum chordata can also be divided as: Urochordata : (a) Salpa and (b) Ascidia 70

15 Sub-Phylum 2: Cephalochordata :- The notochord extends upto the anterior end of the body. Hence, this sub-phylum is named so. The tail is present throughout life, e.g., Branchiostoma (Amphioxus). Amphioxus/Branchiostoma has both ends pointed like lance. Hence, it is commonly called lancelet. Amphioxus Sub-Phylum Vertebrata or Craniata :- These are advanced chordates that have cranium (car-tilage or bony brain box) around brain. Notochord is present only in the embryonic stages. It is replaced by cartilaginous or bony vertebral column (back bone) in the adult forms. They have paired appendages as fins and limbs. Closed circulatory system is present; muscular and ventral heart with two, three, or four chambers; lymphatic system present; erythrocytes and hemoglobin are present. A pair of kidneys is present for excretion and os-moregulation; endocrine glands are well developed; members are generally unisexual and have single pair of gonads. Division 1: Agnatha (Jawless Vertebrates) :- It includes two classes: Ostracodermi and Cyclostomata. They are cold blooded. Vertebral column is represented only by small imperfect neural arches over the notochord. They do not have exoskeleton and paired appendages. The mouth does not possess jaws, hence named Agnatha. They are the most primitive of all craniates. They have single nostril. Internal ear has one or two semicircular canals. Class 1: Ostracodermi :- They were the first jawless fishes (originated in Ordo-vician period in Palaeozoic era). These were shell skinned with exoskeleton of bony plates, e.g., Cephalaspis. Ostracoderms are all extinct now and are called fossil agnatha. 71

16 Class 2: Cyclostomata: Its general characters are as follows :- Circulation is of closed type. Kidneys are mesonephric Single sex organ discharges gametes in the well-devel-oped coelom. Cranium and vertebral column are cartilaginous with persistent notochord. Stomach is absent. Cyclostomes have an elongated body bearing 6 15 pairs of gill slits in their gill pouch for respiration and have a sucking and circular mouth. A single dorsal nostril leads into closed nasal sac. A functional pineal eye is present just behind it. All living members of the class Cyclostomata are ectoparasites on some fishes. The body is devoid of scales and paired fins. Head and brain are poorly developed. They are also called jawless fishes. Table : Difference between lamprey and hagfish (a) Myxine (b) Petromyzon 72

17 POINTS TO REMEMBER :- 1. Typhlosole is a fold of epithelium in the intestine. It prevents the rapid flow of food in the intestine and increases the absorptive surface area. 2. Ammocoete is the connecting link between Amphi-oxus and the cyclostomes. 3. Larva ammocoetehatches out of eggs in about days. The larval period may long from three to seven years. 4. Petromyzon, though marine, goes to fresh water for spawning, i.e., anadromous. After spawning within a few days, they die. 5. Lingual cartilage is also a part of skeleton, that lies in the tongue region and supports it (lingual = related to tongue). Division 2 : Gnathostomata (Jawed Vertebrates) :- Embryonic notochord is usually replaced in adults by a vertebral column. It includes advanced vertebrates. Mouth has jaws, hence it is named gnathostomata. Paired fins or limbs are present. Internal ear has three semicircular canals. Girdles are present. Gnathostomata is divided into two super classes: Pi-sces and Tetrapoda. Paired nostrils are present. Super Class 1 Pisces : Pisces includes true fishes. All are aquatic. The body bears fins. They are cold blooded. The char-acteristics are as follows: Neck absent, no upper or lower eyelids, no tympanum (only internal ear is present). Each eye has a well-de-veloped nictitating membrane. Monocondylic skull; slimy glands present on skin. Respiration occurs typically by gills. Lateral line sense organs are present. Both renal portal and hepatic portal systems are found. Hypophyseal portal system is also present. Scales are mesodermal or dermal and embedded in skin. Vertebrae are amphicoelous type. Heart two-chambered (S-shaped); venous heart with sinus venosus and conus arteriosus. Kidneys are mesonephric, ammonotelic (sharks: ureo-telic). Super class Pisces is divided into three classes: Placodermi, Chondrichthyes, and Osteichthyes. Class I Placodermi (extinct) : It includes the earliest fossil fishes which lived in fresh water. 73

18 Body had an external protec-tive armor of bony scales or plates. Primitive jaws with teeth were present. Skeleton was bony. Fins were mostly formed of large spines, e.g.,climatius (spiny shark). Autostylic jaw suspension; gill slits are covered by operculum. The name placodermi means armoured fish or plate skinned. Both paired and unpaired fins were present. Caudal fin heterocercal. They appeared in Silurian period, flourished in Devo-nian and Carboniferous period, and became extinct in Permian period. Class II Chondrichthyes: This class includes cartilaginous fish, e.g.,scoliodon (dogfish), Torpedo (electric ray), etc. Sharks are fast-swimming predators, whereas the rays and skates are stout, bottom-living scavengers and mollusc feeders. Scoliodon (dogfish) Class III Osteichthyes : It includes bony fishes, e.g.,labeo, Hippocampus, Exocoetus, Catla, Clarias, Betta, Pterophyllum, etc. Bony fishes : (a) Catla and (b) Exocoetus Table : Differences between cartilaginous and bony fishes 74

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20 Some important fishes of super class Pisces 1. Torpedo (electric ray): Torpedo is bottom dwelling, carnivorous fish (Fig. 4.27). It stuns or kills the prey and enemies with electric shock from its electric organs. The latter are modified muscles. The skin is scaleless. Torpdo (electric only) 2. Pristis (sawfish):head bears a series of strong tooth like denticles along the margin (Fig. 4.28). It uses these denticles for offence and defence. It is viviparous. Pristis (sawfish) 3. Exocoetus (flying fish):it does not fly but often leaps into the air upto about 6 m high. The pectoral fins are modified into wing-like structures, with the help of which the fish glides. Exocoetus (flysing fish) 4. Hippocampus (sea horse):the neck and head of the fish are horse like and the tail is prehensile. The male bears a brood pouch in which the female lays eggs and the latter remain there till they hatch. Hippocampus (sea horse) 76

21 5. Labeo (rohu): Labeo rohita and Labeo calbasu are the common fresh water edible carps. It is covered by large overlapping scales. Labeo (rohu) 6. Clarias (cat fish/magur): Indian cat fish (Clarias ba-trachus) 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 Mystus seengala(slinghara), Rita lita, and Wallago attu (Malli). 7. Latimeria chalumnae (coelacanth): It was first caught in 1938 off the east coast of South Africa. It swims by curious rotating movements of its pectoral fins. All its fins except the anterior dorsal are lobed. It is the oldest living fish; and has survived till today without under-going any change in it. It is therefore described as a living fossil. Latimeria (coelacanth) Some important body parts of super class Pisces Fins 1. Paired pectoral and pelvic fins : Act as balancers and brakes; provide lift and counteract pitching and roll-ing. 2. Anterior dorsal fin : Counteracts rolling and yawing. 3. Posterior dorsal and anal fins : Counteract yawing and rolling. 4. Caudal fin : Propels the body and provides lift. POINTS TO REMEMBER :- Types of caudal fin 1. Diphycercal or protocercal : Most primitive kind of tail fin. The tail is symmetrical, both ex-ternally and internally as in protocercal, but it is secondarily symmetrical. 2. Heterocercal/hypocercal tail : Epicaudal and hypocaudal lobes are of unequal sizes. 77

22 3. Homocercal : Identical lobes. Externally sym-metrical and internally asymmetrical. Different type of coudal finas or tails in fishes Endothermic fishes : Although most fishes are ec-tothermic, a few species such as blue fish tuna and swordfish are able to maintain a body temperature higher than the temperature of the water that sur-rounds them. Genetic studies of these endotherms have revealed that the ability to maintain high body temperature gives these fishes an adaptive advantage by allowing them to hunt in much colder waters than their competitors. Fish taken out of water dies of suffocation due to the lack of oxygen. This is because the gill filaments stick together when taken out of water, thereby re-ducing the surface area. Freshwater species Marine species 1. Catla catla (Catla/cat fish) 1. Sardinella (Salmon) 2. Gyprinus carpio (Carp) 2. Hilsa (Hilsa) 3. Labeo rohita (Rohu) 3. Harpodon (Bombayduck) 4. Labeo calbasu (Calbasu) 4. Anguilla (Eel) Some air-breathing fishes used their paired fins to move on land and gave rise to the first land verte-brates. A living fossil of this group is Latimeria, a lobe-finned fish. Scales :- 1. Ganoid or rhomboid:scales are thick, diamond- or rhomboid-shaped plates, e.g., primitive bony fishes such as Acipencer, etc. 2. Placoid:Backwardly directed spine arising from a ba-sal plate, e.g., Chondrichthyes (Fig. 4.34). 78

23 3. Cycloid:Thin, flexible, circular in outline, marked with concentric lines of growth which can be used for determining age, e.g., lung fishes, Amia, etc. 4. Cosmoid:Absent in living fishes; consists of four dis-tinct layers: outermost ganoine, followed by cosmine, spongy bone, and innermost compact bone. Example,extinct fishes. 5. Ctenoid:Bear numerous small comb-like spines, e.g., higher bony fishes such as perch, etc Different types of scales Air bladder : It is associated with respiration, hydrostasis, sound production, and audition. Parental care Nest building, e.g., Gasterosteus, Amia (bow fin), Protopterus, Lepidosiren (nest is built by the males of these fishes). Shelter in mouth, e.g., males of cat fish, Arius. Brood pouch, e.g., male Hippocampus. Table 4.9 Common food fishes of India S.No. Fresh water food fishes Marine water food fishes 1. Catla catla (Katla) Sardinella (salmon) 2. Cirrhina mrigala(mrigal) Hilsa(hilsa) 3. Mystus seenghala (singhara) Anguilla(eel) 4. Labeo rohita (rohu) Stromateus(pomfret) 5. Labeo calbasu (calbasu) Harpodon (Bombay duck) Table 4.10 False fishes in S.No. Common Name Genus Phylum 1. Crayfish Astacus Arthropoda 2. Devilfish Octopus Mollusca 3. Starfish Asterias Echinodermata 4. Hagfish Mysine Chordata 79

24 5. Razorfish/Shellfish Solen Mollusca 6. Jellyfish Aurelia Coelenterata 7. Silverfish Lepisma Arthropoda 8. Cuttlefish Sepia Mollusca 9. Whalefish Balaenoptara Aquatic mammals IMPORTANT POINTS :- 1. Hilsa is the only Indian fish that migrates from sea to rivers for breeding. 2. Most primitive fish (fossil) is Climatius (placodermi). 3. Anabas (climbing perch). It has accessory respiratory organs for breathing atmospheric air which enables the fish to take long overland excursions in search of earthworms. 4. Pomfret is the most widely eaten fish in India. 5. Stone fish is the most poisonous fish. 6. Gambusia fish (larvivorous) was introduced into several tropical regions to control malaria. 7. Catadromous fishes live in fresh water and go down to sea for breeding, e.g.,anguilla (European eel). When fishes migrate from rivers to sea, it is called catadromous migration. Anguilla (European eel) 8. Anadromous fishes live in sea water and move to rivers for breeding, e.g.,hilsa,salmon, etc. When fishes migrate from sea to rivers, it is called anadro-mous migration. 9. Dipnoi has incompletely divided three-chambered heart. 9. Urinary bladder is absent in fishes. 10. Weberian ossicles were discovered by Waber (1820). These connect air bladder with internal ear. 11. Bioluminescent fishes: Anamalops,Porichthyes, etc.; sound-producing fishes: Mola,Batistes. 12. The commercial name of integument of Scoliodon is shagreen. 13. Typical trunk vertebrae of fish are amphicoelous, centrum peculiar as is supported by four wedge-shaped calcified fibrocartilages forming a Maltese cross and leaving uncalcified area. 14. The study of fish is called ichthyology. 15. The study of skates, rays, and sharks is called torpedology. 16. Some elasmobranchs retain urea in blood to maintian hypertonicity. 17. Ampulla of Lorenzini is a thermoreceptor. 18. Electric organs of electric ray are modified muscles. 19. Poisonous glands are found in sting ray, eagle ray, Chimaera,Diodon, and Tetrodon. 20. Fish byproducts are fish meals and fertilizers; fish flour, fish proteins, fish oil, steaming, fish 80

25 glue, leather, artificial pearls, etc. 21. Isinglass is a gelatinous product obtained from the air bladders of certain fishes such as carps, salmons, cat fishes, etc. It is used for making cements, jellies, and for clarification of wines and beers. 22. Crossopterygians (Rhipidistia, Osteolepisgenus) gave rise to amphibia. 23. Parental care is well developed in Hippocampus. 24. Types of vertebrae Types of vertebrae based on the shape of centra in (sagital section) Super Class 2 Tetrapoda: All gnathostomes excluding fishes are included in this super class. They have lungs for aerial respiration. Their sensory organs are adapted for reception in air such as vision, hearing, smelling, etc. Typically all tetrapods (Gk. Tetra= four + podos = foot) possess two pairs of limbs. Skin is adapted to withstand exposure to air. Tetrapoda is divided into four classes: Amphibia, Rep-tilia, Aves, and Mammalia. Class Amphibia : Vertebrates with dual-life (Gk. Amphi = two or both; bios = life). The general characteristics of members of this class are as follows: Kidneys are mesonephric. Urinary bladder is present in frog. Larvae and tailed amphibians (e.g., salaman-ders) are ammonotelic. Frogs and toads are ureotelic. Ear consists of internal and middle ear. Tympanum (outer membrane) covers the middle ear. The middle ear has a single ear ossicle called columella auris. Ten pairs of cranial nerves are present. Sexes are sepa-rate; fertilization is external; oviparous; and develop-ment indirect. They return to water for breeding. Male lacks copula-tory organs. Indirect development occurs. A fish-like stage, the tadpole, is present. The skin is smooth or rough, having cutaneous glands which keep it moist. They are usually without scales, but if scales are present, they are hidden beneath the skin (e.g., Caecilians). Two pairs of limbs are used for locomotion. 81

26 The gills are present at least in the larval stage; some adult forms also carry them in addition to lungs (e.g., Necturus). Alimentary canal and urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior. Skull is dicondylic, i.e., with two occipital condyles for articulation with vertebral column. The respiratory organs are lungs, buccopharyngeal cavity, skin, and gills. There are about 3000 species of amphibians out of which 2600 species are in the order Anura. They are present in the warmer regions of the world except newts and salamander, which are present in cooler regions. They occur only in fresh water and moist land. Am-phibians are not found in sea water. They are poikilothermal animals. They are amphibi-ous in nature, i.e., they can live on land as well as in water. They are mostly found in warm countries. They are ectothermic (cold blooded). Body is divisible into head and trunk. Tail may be present in some forms. The heart is three-chambered, having two auricles and one ventricle. In the heart, there are present sinus venosus and truncus arteriosus. Both hepatic portal and renal portal systems are well developed. Male frog can croak louder than females because of the presence of vocal sacs. Example: Bufo (toad), Rana (frog), Hyla (tree frog), Sala-mandra (salamander), Ichthyophis (limbless amphibia). Living amphibians are divided into three orders: 82

27 Some amphibians belonging to the class Amiphibia IMPORTANT POINTS :- 1. Jaw suspension is autostylic; urostyle is the last com-ponent of vertebral column. 2.The shape of second to seventh vertebrae is procoe-lous (typical); eighthvertebra: amphicoelous; ninthvertebra: acoelous. 3. Amphiuma has the largest RBCs among vertebrates. 4. At the time of metamorphosis, tadpole does not feed. 5. Blind worms (limbless amphibians) are unusual am-phibians as only one species lives in water. All the other burrow underground and are rarely seen on the surface. Many do not even need water to breed. 6. Word roots and origins a. Caudata: From Latin, Caudata meaning tail. b. Nictitating: From Latin, nictare meaning to wink. 7. Seymouria is a connecting link between amphibia and reptiles. 8. Paedogenesis:Development of gonads and/or pro-duction of young ones by immature or larval forms, e.g., salamander (Ambyostoma). 9. Total neoteny is shown by Necturus,Siren, and Proteus. 10. First toe is called hallux. 11. Carboniferous period is known as the age of amphib-ians. 12. The arrow poison frogs secrete a powerful poison from the skin which can cause instant death. 13. The most poisonous frog Golden dart poison frog is from South America. One adult frog con-tains enough poison to kill 200 people. 83

28 14. Toads are used in chinese medicines. The skin of toad secretes a substance that increases the blood pressure when injected into humans. 15. Some frogs have development in amazing ways to prevent their eggs from drying out. The female su-rinam toad of South America carries her eggs in the pits/pockets of skin on her back. As many as 60 young ones pass through the tadpole stage while em-bedded in her back and then emerge as small frogs. 16. In frogs, external ears are absent, only tympanum is seen externally. Frogs have a tympanic membrane on the surface of both sides of their head. The tympanic membrane of a human are called eardrums and each is protected inside ear canal. 17. The skin of tadpole also secretes an enzyme, diastase. 18. The upper jaw of frog is derived from quadrate carti-lage whereas the lower jaw is derived from Meckel s cartilage. Class Reptilia : Their name refers to their creeping or crawling mode of locomotion. Kidneys are metanephric. Excretion is uricotelic. Urinary bladder is absent in snakes and crocodiles. Cranial nerves are in 12 pairs. Jacobson s organ (vomeronasal organ) present in the roof of buccal cavity, concerned with smell, is well developed in snakes and lizards. They do not have external ear openings. Tympanum represents ears. Sexes are separate. Males usually have a muscular copulatory organ. Fertilization is internal. Mostly are oviparous and development is direct. Some are viviparous. No metamorphosis. Reptiles are cold-blooded or poikilothermic animals. There are only about 6000 species of reptiles now liv-ing. But fossils show that 200 million years ago, the reptiles were the most dominant animals on earth. Herpetology is the study of reptiles. Mouth is terminal with conical teeth which are pleurodont in lizards and snakes and thecodont in crocodiles. Teeth are absent and replaced by horny beaks in turtles. Endoskeleton is bony; skull is monocondylic (with one occipital condyle). Heart is usually three-chambered or partially four chambered. Interventricular septum is incomplete. Heart is completely four chambered in crocodiles. Two systemic arches are present. Erythrocytes are oval and nucleated. The largest reptiles today are the komodo dragon Varanus komodoensis of Indonesia (a lizard) 3 m in length, crocodiles (up to 7 m), pythons (up to 10 m), and giant tortoises weighing up to 600 kg. They are covered by dry and cornified skin having epi-dermal scales or scutes. Snakes and lizards shed their scales as skin cast. Scales prevent loss of body water and so reptiles do not require a moist environment like amphibians. Respiration is only through lungs, which is improved by the development of ribs. Limbs when present are in two pairs; pentadactyl; digits have horny claws. 84

29 (a) Chabeleon, (b) Crocodilus, (c) Chelone, and (d) Naja 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), etc. Classification of reptiles is based on the temporal fossa of skull. The class Reptilia is first divided into five sub-classes: (1) Anapsida, (2) Euryapsida, (3) Parapsida, (4) Synapsida, and(5) Diapsida. Out of the five sub-classes, the living reptiles are found only in two sub-classes: (1) Anapsida and (2) Diapsida. 85

30 1. Anapsida: Primitive reptiles with a solid skull roof. No temporal openings/fossae. Order : Chelonia Commonly called turtles (marine), tortoise (terrestrial), and terrapins (edible freshwa-ter). Body encased in two shell plates, dorsal cara-pace, and ventral plastron. Limbs clawed, webbed, or paddle-like. Sternum is absent. Jaws with horny sheath, no teeth. Certain aquatic turtles perform cloacal res-piration, but all other reptiles re spire with lungs. Cloacal respiration is reported. Table 4.11 Difference between tortoise and turtle Tortoise Turtle 1. Forelimbs and hindimbs are not 1. Forelimbs and hindimbs are modified into paddles. modified into paddles. 2. Head can be completely with drawn 2. Head is partially withdrawn into the shell. into the shell. 3. It has oval carapace. 3. It has heart-shaped carapace. 4. It is usually larger in size. 4. It is comparatively smaller in size. 5. It is semi-terrestrial and fresh 5. It is an aquatic and marine form. water form. 2. Diapsida a. Order: Rhynchocephalia Sphenodon is a protected animal under the law of New Zealand government. An interesting feature of Sphenodon is the presence of pineal or parietal or third eye. All are extinct except a living species Sphe-nodon punctatum. Sphenodon is Tuatara of New Zealand. It is a living fossil and going to become extinct. Sphenodon is referred to as a living fossil because it has retained many primitive characteristics of fossil or stem reptiles. b. Order : Squamata Serpentology or ophiology is the study of snakes. Lizards have four well-developed pentadac-tyl limbs with claws. Example, Calotes (gar-den lizard). Divided into two sub-orders: Lacertilia (liz-ards) and Ophidia (snakes). The glass snake Ophiosaurus derives its name from its ability to break off its tail when seized. Lizards are mostly comivorous, but a herhiv-orous lizard is lguana from South and Central America. 86

31 Saurology is the study of lizards. The tail of most lizards is easily broken off when threatened or seized by a predator. This ability is known as autotomy. Autotomy is the voluntary breaking of tail to confuse the enemy. Heloderma rarely bites humans, but its bite is fatal. Its poison is neurotoxic. Limbs are absent in lizards such as Ophio-saurus, Anguls, and Rhineura, also called glass snakes. A limbless lizard can be distinguished from snakes by the presence of movable eyelids and external ear opening. Barkudia is a limbless lizard from South India. A new tail is soon regenerated which, how-ever, does not possess vertebrae. Most lizards are oviparous, two viviparous lizards are Phrynosoma (horned toad) and Chameleon (tree lizard). Draco is a lizard which glides with the help of patagium and hence called flying dragon. Heloderma (gila monster) is the only poison-ous lizard in the world. It is also called beaded lizard because its scales resemble beads. There are two species of heloderms, H. sus-pectum and H. horridum. Both are found in America. The largest living lizard in the world is the ferocious dragon, Varanus komodoensis, found in Malaya Archipelago, Length is 2.5 m, weight over 100 kg. IMPORTANT POINTS Snake charming Raising its head and spreading its hood, the cobra gets ready to strike the moving flute tip. The charmer knows the striking distance and adjusts himself so that the snake orients towards the waving flute but keeps beyond the strike distance. Contrary to general belief, the snake charmer s cobra does not dance the tune of the flute. Rather it follows the movement of the tip of the flute and the swaying body of its master, who really moves with the rhythm of the music. Rattle snake muscles Most muscles would quickly tire from this kind of energetic activity, but the rattle snake can shake its tail for long periods of time. The muscle s ability to use ATP in an efficient manner allows it to sustain a high level of activity. Rattle snakes have the quickest moving skeletal muscles in the animal world. Their tail muscle allows them to shake their rattle 90 times each second. 87

32 Identification of poisonous and non-poison-ous snake 88

33 c. Order : Crocodilia Differences between crocodile, alligator, and Gavialis (a) Crocodylus palustris (indiann freshwater crocodile), (b) Alligator missisiplensis (american alligat), and (c) Gavialis gangeticu (gavial or gharial) IMPORTANT POINTS Many sea snakes are viviparous. Pit vipers are also mostly viviparous. The oldest living animal in any Indian zoo is the Al-dabra giant tortoise. Rattle snake s tail emits a frightening sound which scares away the enemy. The king cobra of India is the only snake in the world that builds a nest. Benadryl is used as an antidote to counteract the effect of hemotoxins. Seymouria is considered as the connecting link between amphibians and reptiles. Mesozoic era is known as age of reptiles. Loreal pit of pit viper is a thermoreceptor organ. Reptiles without urinary bladder are snakes, croco-diles, and alligators. Largest snake is python; smallest snake is thread snake. Largest lizard is Komodo dragon; smallest lizard is two species of dwarf gecko. Longest dinosaur is Diplodocus; smallest dinosaur is Compsognathus. Ophiosaurus is known as glass snake, blind worm, or slow worm, limbless lizard. Anguis is also known as blind worm and is limbless. Most poisonous snake of the world is peninsular tiger snake. Poisonous sea snake: Hydrophis Heaviest dinosaur is Brontosaurus. Largest living reptiles are (1) python, (2) crocodile, and (3) Komodo dragon. 89

34 Hemidactylus or wall lizard (gecko) is a swift run-ner on smooth vertical surface due to the presence of vaccum pads. Draco is a flying lizard but it actually does not fly. Heloderma is a poisonous lizard (gila monster). Biggest flesh eater dinosaur is Tyrannosaurus Horned dinosaur: Stegosaurus Largest living carnivorous reptile is Crocodilus. Thermomorpha is a group of reptiles which are con-sidered to be the ancestors of mammals. Hedonic glands present in males secrete a sticky sub-stance which hardens structures such as spine and helps to hold the mate firmly. In Uromastyx, cloaca possesses a pair of copulatory organs called hemipenes. Russel s viper is the largest Indian viper. Hafkine Institute of Bombay is the main center where antivenom is produced. Monitor lizard (Varanus) is the largest living lizard. Varanusis commonly called Goye or monitor ; semi-aquatic; slightly laterally compressed tail. Carapace is hard shield like structure present on the dorsal surface of tortoise and turtle. Reptiles arose in the lower carboniferous time, from labyrinthodont amphibia. Phrynosoma is found in deserts; called horned toad, skin hygroscopic; takes water in the form of dew; exudes red blood like stream from eyes, when-ever, terrified. Iguana is 5 6 feet long; body and tail laterally com-pressed; arboreal in habit; herbivorous found in trop-ical America. Sphenodon is the only living genus of Rhynchoce-phalia. It is commonly called Tuatara. It is found only in New Zealand. It is called a living fossil as it resembles with Hanaesaurus of Jurassic age. The limbs of Chameleon show syndactyly (fusion of digits) as an adaptation to arboreal life to form op-posable finger to hold the twigs. Class Aves (birds) : The study of birds is known as ornithology. The general characters are as follows: Jaw bones are prolonged into a toothless beak or bill. Oesophagus is dilated into a crop for quick feeding and storage. Crop secretes pigeon milk during breeding season. Stomach is divided into a glandular proven-triculus and a muscular gizzard. The junction of small intestine and rectum is marked by a pair of rectal cecae. Cloaca of birds is three-chambered: antenior copro-daeum, middle urodaeum and a large posterior procto-daeum. There is no gall bladder in birds like pigeon. Limbs are two pairs. Forelimbs are modified as wings for flying. Hindlimbs or legs are large, each foot usu-ally bears four, clawed toes. Hindlimbs generally have scales. Birds are feathered bipeds, air breathing, truly flying vertebrates (other being bats from class Mammalia). 90

35 Exoskeleton consists of feathers, scales, and claws, which are epidermal derivatives. Skin without glands; the only cutaneous gland is uropygial gland or preen gland/oil gland at the base of the tail. Respiration is due to compact, spongy, non-disten-sible lungs continuous with thin-walled air sacs. Air sacs reduce body weight, helps in double respiration and internal cooling. Larynx is present without vocal cords. A sound box or syrinx producing voice lies at or near the junction (furcula) of trachea and bronchi. Furcula Kidneys metanephric and three-lobed. Ureters open into cloaca. Urinary bladder is absent. Excretion is uricotelic. Heart is completely four-chambered as in mammals. Sinus venosus absent. Only right aortic (systemic) arch persists in the adults. The renal portal system is vestigial. Erythiocytes are minute, oval, and nucleated. The blood of the birds may be called the richest blood in the animal kingdom. It has more RBCs per cubic mm of blood than in any other animal. Cranial nerves are of 12 pairs. Olfactory organs are poor. Middle ear contains a single ossicle. Eyes possess nictitating membrane. Pecten is a comb-like structure found in the eyes near blindspot. Pecten helps in the nutrition of eyeball. Pecten is found in all birds except Kiwi. Sexes separate. Some birds show sexual dimorphism (e.g., parrot and peacock). Male bird has a pair of ab-dominal testes and a pair of sperm ducts. A copula-tory organ is absent in all birds except in ratitae, geese, ducks, etc. Females are oviparous with a single (left) functional ovary and oviduct (Mullerian duct). Devel-opment is direct. Different parts of oviduct secrete the following: Ostium Dense albumin Magnum White albumin Uterus Calcareous shell Birds are the first vertebrates to have warm blood. Body temperature is regulated (homoiothermous). Ala spuria (bastard wing): Feathers on first digit (thumb). Eggs of birds are cleidoic (with calcareous shell), mac-rolecithal (amount of yolk), mesolecithal (distribution of yolk). Extraembryonic membranes are present (amniota). Feathers are found only in birds. Feathers are made up of a protein keratin and are water proof due to the oily secretion of preen glands. The arrangement of feathers on the body of birds is called pterylosis. The feather-less areas are called as apteria. Four types of feathers are: quill feathers, contour feathers, filoplumes, and down feathers. In the absence of down feathers, the birds will not be able to keep the body warm. Quill feathers in the wings are called remiges. Quill feathers in the tail are called rectrices. Filoplumes and down feathers help in the insulation of the body. 91