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Division (2) (1) These are developed . (2) Mouth is encircled by true . (3) Movement by paired or legs. (4) Vertebral column well developed. (5) Mouth is not rounded. (6) Pineal eye is absent. (7) 3 Semi circular canals are found in internal ear. (8) are unisexual, gonads are paired, genital ducts are present. (9) or lungs are meant for respiration. Group Gnathostomata is classified into two super classes on the basis of locomotory organs, respiratory organs, heart, nostrils and vascular system.

[2] Super of G-nathostomata : [1] Pisces [2] Tetrapoda

[1] SUPER CLASS - PISCES (1) This superclass includes true . (2) Animals are aquatic, may be fresh water or marine. (3) These are cold blooded or poikilothermic animals. (4) Body is long, boat shaped and stream lined, which is divided into , trunk and tail. Neck is absent. (5) Body is covered by dermal scales. Exceptions :- 1. Cat 2. Torpedo Both these fishes are less. (6) Paired fins are present for swimming, e.g. Pectoral and pelvic fins, along with these fins are also found on the body e.g. mid dorsal and caudal fin. (7) Endoskeleton is made up of or . (8) External nares are one pair. This condition is known as Dirhynous condition. (9) Respiration by gills, gills are 5 to 7 pairs and naked or covered by operculum. (10) Heart two chambered, known as “Venous heart”, because it contains only impure blood, which goes to gills for purification from heart. Pure blood is then distributed to all parts of body directly from gills, i.e. circulation of blood is unicircuit. (11) Their RBC (Present in blood) are nucleated. Sinus venosus, renal and hepatic portal systems are found in circulatory system. (12) External and middle ears are absent, only internal ear is present in which three semi - circular canals are present, which work as statoreceptor. (13) Kidneys in fishes are mesonephric type. Cartilagenous fishes excrete urea and marine bony fishes excrete trimethylamine oxide. (14) Cranial nerves are 10 - pairs. (15) Lateral line receptor system is present in the body of fishes, which includes many organs. (16) “Air bladder” helps in respiration in lung-fishes (Group - Dipnoi) (17) Vertebrae in fishes are amphicoelus, in which centrum is concave at both the surfaces. (18) Fishes are unisexual. (19) Fertilization is internal or external. Females are oviparous or ovoviviparous. (20) In the skull of fishes only one occipital condyle is present, so their skull is called monocondylar type. (21) Eggs are mesolecithal or megalecithal type. (22) Cleavage in fishes is holoblastic unequal, or meroblastic discoidal type. (23) Extraembryonic membranes are absent in fishes so all the fishes are placed under anamniota. (24) Metamorphosis is direct i.e. larval stage is lacking during development. (25) Small fishes (Baby fishes) are called “FRY”. (26) Fishes show a seasonal migration in a particular season. [A] Migration of fishes from fresh water to marine water is called catadromous migration. Example :- Anguilla [B] Migration of fishes from marine water to fresh water is called Anadromous migration. Example :- (1) Salmon (2) Sturgeon (3) Hilsa (4) Trout (27) “ era” is called “era of fishes” Study of fishes is Icthyology. Romer classified super class pisces into three classes :- Super Class Pisces classify into three classes :- (A) Class - (B) Class - (C) Class -

(A) CLASS - PLACODERMI :-

(1) In this class, all extinct fishes are included, which lived from devonian period to pe- riod. So these were the “first fresh water true fishes”. (2) Their entire body was covered by bony plates, so these were called “Armoured fishes” Examples 1. Dinicthyes 2. 3. Climatius - first jawed fish

(B) CLASS CHONDRICHTHYES OR ELASMOBRANCHI :-

(1) This class includes cartilagenous fishes. (2) Fishes are normally marine of this class. (3) Endoskeleton is made up of cartilage. (4) Exoskeleton over the skin is made up of placoid scales. These scales are like denticle and are originated by dermis of skin. (5) In these fishes, 5-7 pairs of gills are present, which open directly outside the body by slits, operculum is normally absent in these fishes. (6) 5 pairs spiracles are found in them. Exception :- Fishes of group have operculum over their gills. Example :- (Rat fish) 5. Stegostoma :- Tiger 6. Trygon :- Sting ray - Its has poisonous spines. 7. Torpedo :- - In this fish an electric organ is found which is a modified muscle it can give shock of about 100 volts. It is exoskeletonless. 8. Rhineodon :- Whale shark - It is the largest true fish. Its length is 13 - 14 mt 9. Carcharodon :- Greate white shark. 10. Chimaera :- “Rat fish” or “King of herrings” or ghost fish. Chimaera is supposed to be the connecting link between bony and cartilagenous fishes. 11. Raja :- Scate 12. Myliobatis :- Eagle - Ray Note :- Dry skin of cartilagenous fishes is called “Sagreen”

[C] CLASS - OSTEICHTHYES OR :-

(1) Fishes of this class are found in fresh water as well as marine water. (2) Body is spindle shaped and boat - shaped. (3) Their exoskeleton is made up of scales, which may be cycloid or ctenoid or ganoid Placoid scales are absent. (4) Mouth is normally terminal or subterminal, teeth are found in Jaws. (5) Endoskeleton of these fishes is made up of bones, so these fishes are called “bony - fishes” (6) is modified into vertebral column. Pelvic girdle is simple, small or may be absent. (7) Respiration by 4 - pairs of gills. These gills are covered by operculum at each side of body. (8) Spiracles are absent. (9) Helping respiratory organs “air-bladders” are present. Lung fishes respire through air bladders. In other fishes these air bladders are hydrostatic i.e. help in maintaining balance of body. (10) Scroll valve in intestine and ampulla of Lorenzini are absent. (11) Internal nares are present. (12) Liver is trilobed. (13) Cloaca absent, in place of cloacal aperture anus is present. (14) Tail is normally homocercal type but sometimes it may be diphycercal type. (15) Heart two chambered, sinus venosus and bulbous arteriosus are present. (16) Genital ducts open outside the body through separate apertures. (17) These fishes are unisexual. (18) Fertilization is external and claspers are absent in male fishes. (19) Female fishes are oviparous but may be ovoviviparous Examples (1) Labeo :- “Rohu”or “Indian carp” - It is a fresh water fish. (2) Clarius :- “Cat fish” or magur (3) Hippocampus :- “Sea - horse” or “Pregnant male” :- It swims in water in its vertical position. A pouch like structure is present at the abdomen of male fishes known as “Brood - pouch”. In this pouch male collects the eggs. Secondary vivipary and parental care is found in hippocampus. (4) Anabas :- Climbing perch. (5) Exocetus :- Flying fish - Its dorsal fin is long, it can fly (glide) over 400 metre with the help of this fin. (6) Amia :- Bow - fish. (7) Anguila :- :- Its body is like (8) Acipensor :- Sturgeon - endoskeleton is made up of . (9) Echeneis :- Sucker fish - Dorsal fin modified into suckers. Shows commensal with shark. (10) Pleuronectus :- Flat fish (11) Latimaria :- Living fish :- It is the oldest living known till now. (12) Opsanus :- Toad fish (13) Syngnathus :- Pipe fish (14) Synanceja horrida :- Stone fish .- It is the most poisonous fish. (15) Lepidosteus :- - pike (16) Harpodon :- Bombay duck. (17) Gambusia :- Larvivorous fish. (18) Fistularia :- Flute fish. Dipnoi :- These are called “lung fishes”, because their air bladder help in respiration. (1) External and internal both the nares are present. (2) Their tail is heterocercal type. These are freshwater fishes. Fishes of dipnoi group are called Lung - fishes or “Uncle of ” Example

1. : African lung fish :- It is living fossil fish. 2. Lepidosiren :- South american lung fish. 3. :- Australian lung fish. SPECIAL (IMPORTANT) POINTS (1) Cycloid, ctenoid, ganoid scales are mesodermal in origin. (2) Scroll valve present in the intestine of some fishes increases the absorptive surface area. (3) Scoliodon and Mustellus fishes are viviparous.

Fish liver oil is rich in Vit - A & D Shark liver oil is rich in Vit - A Cod liver oil is rich in Vit - D (4) Lung fish remains alive outside the water, but rest of the fishes require water for gill respiration. (5) Fishes can change their direction of swimming at any time by their caudal fin. (6) Egg capsule of and Skates refers to “Mermaid purse” (7) Issinglass is gelly like substance obtained from air bladder of certain fishes it is used for clari- fication of wines and Beers. (2) Superclass - Tetrapoda (1) Members of this superclass are found in water and on land. (2) Locomotion by 2 pairs of pentadactylous limbs. (3) Gills are present only in embryonic stages. Main respiratory organ in adults is lung. (4) Exoskeleton is made up of scales, feathers or hair. (5) Endoskeleton is made up of bones. (6) Heart is three or four chambered and double circulation is found in them. (7) Kidneys are mesonephric or metanephric type. (8) Middle ear is present. and have external ears also. Superclass - Tetrapoda is divided into four classes Class [A] - Amphibia Class [B] - Reptilia Class [C] - Aves Class [D] - Mammalia

Class amphibia includes amphibious animals which can live on both the places i.e. - under water and on the land. These are the first animals which come out from the water but these are not able to live on land permanently, they depend on water for their reproduction. Class amphibia shows the double nature of animals. Amphibia class is placed between pisces class and reptilia class and they are originated in Devonion period. period is the age of Amphibians. Main Features :- (1) Body is divided into head, trunk and tail. Some amphibians lack tail e.g. frog, toad etc. (2) Skin is smooth and mostly scale less, but whenever scales are present there are embeded in the skin. e.g. in Ichthyophis. (3) Numerous glands are found in skin which helps in moistening the skin. So these animals respire through moist skin. Some poisonous glands are also found in the skin of some animals e.g. Bufo. (4) These are cold blooded or poikilothermal animals. (5) Two pairs limbs help in swimming in water or moving on land, forelimbs have four fingers and hindlimbs have five fingers. (6) Two nostrils are found , this condition is called dirhynous. (7) Skull has two ocipital condyles, with the help of these two condyles skull is connected by first vertebra of vertebral column i.e. Atlas, this type of skull is called dicondylic skull. (8) Respiration by gills, skin, lungs or buccopharyngeal cavity. But most of respiration is through the skin. (9) Heart is three chambered, 2 auricles and 1 ventricle. Trunkus arteriosus is well developed. (10) R.B.Cs are biconvex, oval and nucleated. (11) Their digits do not have nails or claws at all. (12) Mouth is bigger in size. Upper or both the jaws have similar teeth. these are pleurodont, homo- dont and polyphyodont. (13) Endoskeleton is made up of bones, but cranium is cartilagenous. (14) A well developed and complete alimentary canal along with digestive glands are present in diges- tive system. (15) Ribs absent, but may be present in some animals, but ribs are not attached with sternum. (16) Cranial nerves are 10 pairs. (17) External ear absent, only one ear ossicle, columella is present in middle ear. (18) 1 pair of kidneys work as excretory organs. These kidneys are mesonephric or opisthonephric type. These animals are Ureotelic. (19) These animals undergo hibernation or aestivation period for the protection of the body from extreme cold and heat and to overcome unfavourable conditions. (20) Alimentary canal, urinary bladder and genital ducts open into cloaca. (21) Lateral line sensory system is necessarily found in any stage of development. (22) Pigment cells are found in skin which form chromatophores, due to the presence of External chromatophores skin becomes coloured. (23) Vertebrae in these animals are procoelus type, in which centrum is concave from anterior side and convex from posterior side. (24) These are unisexual animals, males have copulatory organs sometimes. These animals return to water from land for their reproduction. (25) Fertilization is external and inside the water, but some animals show internal fertilization. (26) These are oviparous, which lay their eggs in water. Eggs are mesolecithal. Extraembryonic membranes are absent, so these are placed under anamniota group. (27) Pipa americana - Surinam toad, secondary vivipary is found. (28) In these animals, renal portal system and hepatic portal system are found. (29) Cleavage in eggs is holoblastic and unequal. (30) A gelatinous covering is found over eggs. (31) Development is indirect type i.e. tadepole larva - In frog, Axolotl larva - In salamander This class is divided into three orders :- (a) Gymnophiona or Apoda (b) Caudata or Urodela (c) Anura or Salientia

(A) ORDER - GYMNOPHIONA OR APODA (1) Their body is worm like. (2) These are primitive amphibians, burrowing in nature. (3) Their body is naked and limbless. (4) Skin is soft, and moist with mucous glands, small scales are found on the skin. (5) Their eyes are covered by opaque skin. Middle ear and tympanic membrane absent. So these are blind and deaf. (6) Girdles are absent. (7) Protursible copulatory organ is present in male. (8) Dermal bones are present in cranium. (9) Parental care is found in them. (10) Tail ill developed or absent. Example 1. Ichthyophis :- blind worm 2. Uraeotyphlus :- Dermal scales are found in the skin. 3. Gymnophis 4. Apodon

(B) ORDER - CAUDATA OR URODELA (1) Body is distinctly divided into head, trunk and tail. (2) Normally two pairs of limbs are found which are of equal size. Sometimes hind limb is absent. (3) Skin is scale less. (4) Both the jaws have teeth (5) External gills are present only in larval stage. (6) Copulatory organ absent in males. (7) Vertebrae are numerous, their centrum is amphicoelus or opisthocoelus type. (8) Characterstic feature of this order is Neoteny. Larva attains sexual maturity without undergoing metamorphosis, and starts reproduction. (9) Different types of salamanders are included in this order. Examples

(1) Salamendra :- It is viviparous. Its larva is called Axolotal larva. It sometimes show neoteny. (2) Proteus :- Cave - salamender (3) Necturus :- Water dog or mud puppy. It shows permanent neoteny. Its larva never be adult. (4) Amphiuma :- Congo-eel - largest RBC is present here approximately 90 mm size. (5) Ambystoma :- Tiger salamender (6) Siren :- Mud - eel (7) Triton :- Crested newts. [Newts = Lizard like ]

[C] ORDER - ANURA OR SALIENTIA (1) These are specific animals, where tail is absent in adult stage. (2) All the frogs and toads are included in this order. (3) Skin is moist with mucous. (4) 2 pairs of limbs are found. Fore limbs are short and hind limbs are long. Digits of hind limb are webbed, which help in swimming. (5) Gills are absent in adults. (6) Ribs reduced or absent. (7) Vertebral column small, in which only 5-9 vertebrae are found, last vertebra is stick like urostyle. (8) Eyes with lids, tear glands present. (9) Tympanic membrane present. (10) Egg laying, fertilisation and development is always in water. (11) These have power of voice. (12) Development indirect i.e. tadpole larva is found in them. (13) Metamorphosis complete. Examples 1. Bufo = common toad [Poision glands are modification of parotid gland]. 2. Hyla = Tree - frog 3. Rana tigrina = Indian bull frog 4. Rhacophorus = Flying frog 5. Alytes = Midwife toad - Parental care is well developed in them. Male toads carry eggs in their limbs. 6. Pipa americana = Surinam toad - secondary vivipary is found in them. 7. Rana goliath = Largest frog 8. Bombinator = Fire belly toad. 9. Mototrema = Marsupial frog Points to Remember :- Suspensorium of jaws in amphibia is autostylic type. Fertilization is internal in apoda and urodela. All the amphibians are found in fresh water, except Rana concriona. These animals are not found in marine water normally. Mentomechanial is found in Rana tigrina. A small anterior most part of Makel’s cartilage is ossiffied and form a “Replacing bone” called Mentomechalian bone. The branch of which deals with the study of is known as “Herpatology”. Reptilians are supposed to be the first successful terrestrial animals. Reptilians were dominating in mesozoic era, so Mesozoic era is called “golden age of reptiles”. In the same era, giant dinosaur’s and plesiosaurus dominated over the earth (land) as well as sea water. Reptiles are the first amniotic vertebrates, whose embryos have embryonic membranes. Group Amniota includes Reptilia, Aves and mammalia. Reptiles are supposed to be developed from special amphibians ancestors in carboniferous period.

GENERAL CHARACTERS :- (1) These are, normally, terrestrial animals, but some animals are aquatic in nature also. (2) Their skin is dry, rough, nonglandular and cornified. (3) Body is divided into head, neck, trunk and tail. (4) Their exoskeleton is made up of horny epidermal scales or bony scales or bony plates. (5) In these animals, each limb has five digits. Each digit has incurved nails. Some lizards and do not have limbs e.g. ophiosaurus lizard is a limbless lizard. (6) Endoskeleton of these animals is made up of bones. (7) Only one occipital condyle is present in skull, this type of skull is called monocondyl skull. (8) Respiration in these animals is by lungs, through out the life, but members of order Chelonia can respire through their cloaca, it is known as “Cloacal respiration” (9) Ribs are present in neck and . Ribs of thoracic region make true sternum. (10) Teeth are acrodont and thecodont type. (11) In these animals, heart is incompletely four chambered, 2 complete auricles and two incom- plete ventricles. But ventricle of animals of order crocodilia is completely divided into four chambers, i.e. heart is four chambered in crocodiles. (12) Sinus venosus is ill developed RBCs are oval and nucleated. (13) One pair of metanephric kidneys help in excretion. These animals are uricotelic for water conservation. (14) Right and left both the systemic arches are present in these animals. (15) There are 12 pairs of cranial nerves in these animals. Brain is well developed and cerebrum also developed. (16) Lateral line system is absent. At the roof/ceiling of buccal cavity Jacobson’s organ is present. (17) A complete alimentary canal is found in these animals, which opens into cloaca. (18) Genital aperture is not separate from anus. Ureters, genital ducts and alimentary canal open into a single cloacal aperture. (19) Centrum of vertebrae are procoelus type. Sternum is well developed. Sternal ribs are found in reptiles. A chevron bone is found in caudal vertebrae of these animals. (20) These are cold blooded, poikilothermal animals. Their body temperature varies according to climate. (21) These are unisexual animals. Fertilization is internal. One (or two) penis is found in male animals as copulatory organ. (22) These are mostly oviparous, but some animals are viviparous also. Amount of yolk is much in their eggs, i.e. eggs are polylecithal.

Eggs are cleidoic, i.e. eggs are covered by a shell made up of CaCO3. Cleidoic eggs is an adaptation for terrestrial habitat. (23) Cleavage is discoidal & meroblastic. (24) There are found all the three embryonic membranes amnion, chorion and allantois in the Yolksac also attached with embryo. So this class is grouped under Amniota group. (25) Development direct i.e. larva stage is absent. (26) Parental care is often marked. Class Reptilia is classified on the basis of the number and presence or absence of temporal fossae in the temporal region of skull. Class reptilia is divided into five sub classes :- (1) Anapsida (2) Euryapsida (3) Parapsida (4) Synapsida (5) Diapsida Out of these sub classes Euryapsida, Parapsida and Synapsida are totally extinct.

(A) SUBCLASS - ANAPSIDA :- (1) Temporal fossae are absent in the temporal region of the skull i.e. roof of skull is complete. (2) Limbs are strong. The members of this subclass are classified into two orders in which only members of one order are alive.

(I) ORDER - COTYLOSAUREA :- All the members of this order have become extinct. e.g. Cotylosorus

(II) ORDER - CHELONIA :- Order - Chelonia (1) Body is broad and oval. (2) They are terrestrial, marine and fresh water animals. (3) This order includes live and extinct both the animals. (4) Whole body is covered by firm bony shell. Exoskeleton of dorsal region of body called carapace and of ventral region of body is called plastron. (5) Jaws are horny and teeth less beak like jaws are found. (6) Sternum is absent. Bony plate present on the body are called osteoderms. (7) Nails are found on digits. Web or membrane is found in the digits for swimming. Scales are found on neck, limbs and tail. All these three organs can be pushed into the carapace. (8) Quadrats bone is fixed. (9) Thoracic vertebrae and ribs are attached with carapace. (10) Cloacal aperture is vertical and it helps in respiration. (11) Single copulatory organ is found in male animal. (12) Animals are oviparous. Examples

1. Testudo :- Land tortoise 2. Chelone :- Marine (tortoises) turtles 3. Trionyx :- Freshwater terrapins. 4. Kachhugotactum = Roofedtactum

(B) SUB CLASS - EURYAPSIDA :- All species are extinct..

(C) SUB CLASS - PARAPSIDA :- One pair superior temporal apertures/fossae are found in skull. All species of this subclass are extinct.

(D) SUBCLASS - SYNAPSIDA :- One pair of inferior temporal fossae are present in skull. All the species are extinct.

(E) SUBCLASS - DIAPSIDA .- (1) One pair superior and one pair inferior temporal fossae are found in the temporal region of skull. (2) Post orbital and squamosal bones separate the superior and inferior temporal fossae. Subclass Diapsida is classified into two super orders :- (1) (2) Archosauria

(1) SUPER ORDER - LEPIDOSAURIA :- This super order is classified into two orders.

(A) ORDER : RYNCHOCEPHALIA :- (1) Most of the species of this order are found in the form of . Only Sphenodon punctatum species is living. It is found in New Zealand. (2) Body is small and lizard like. Tail is laterally compressed. (3) Limbs are pentadactyl and digits are with nails. These form furrows in land. (4) Dorsal surface of the body is covered by scales and there is found a spiny scale dorsal line of the body. (5) A functional third eye or pineal eye is found on the head. (6) Vertebrae are amphicoelus type. (7) Teeth are acrodont type. (8) Cloacal aperture is transverse. (9) Penis or copulatory organ is absent in male animals. (10) Their age is about 100 years. Example

1. Sphenodon punctatum :- It is also called ‘Tuatara’. It is found only in New zealand. It is a living fossil. It is supposed to be the connective link between fishes and amphibia.

(B) ORDER - SQUAMATA :- (1) Largest number of species of reptiles of present time are found in this order. All the lizards & snakes are included in this order. (2) One or two pairs of temporal fossae are found in temporal region of skull, which disappear after sometimes. (3) Limbs clawed but they are absent in snakes and some of the lizards. (4) Horny scales are found on body, i.e. their exoskeleton is made up of horny plates. (5) Vertebrae are procoelus type. (6) Ribs are having only one ending. (7) Teeth are pleurodont, i.e. tooth is situated at lateral side of bone. (8) Penis (in males) is double and eversible. Order squamata is divided into two suborders Suborder : (i) Lacertilia and (ii) Ophidia

(I) SUB ORDER - LACERTILIA :- (1) Normally we call the members of this suborder “Lizards”. (2) Study of lizards is called “Saurology”. (3) Limbs and girdles are well developed in these animals. (4) Eyelids are movable and nictitating membrane is found in eye. (5) Auditory aperture or auditory opening and tympanum is present (6) Foramen of penizzae is found in the heart of lizards. (7) Sternum and episternum is present, urinary bladder is also present. (8) Only superior temporal fossae are present, inferior temporal fossae are absent. Both the lungs are equally developed. (10) Maxilla, palatine and pterygoid bones are fixed/stable in the skull. Examples