Class Reptilia (rep-til+e-a) (L. repere, to creep): reptiles.

3. Class Reptilia (rep-til+e-a) (L. repere, to creep): reptiles. • Ectothermic tetrapods possessing lungs; embryo develops within shelled egg; • No larval stage; skin dry, lacking mucous glands, and covered by epidermal scales. • About 8100 species.

4. Reptiles have many terrestrial adaptations • Many reptilian characters are adaptations to terrestrial life. • The dry reptilian skin does not allow effective gas exchange. prey.

5. Like fishes and amphibians, extant reptiles generally lack metabolic mechanisms for regulating body temperature. • They are ectothermic, meaning that their body temperature fluctuates with the temperature of the surrounding environment. • Some reptiles have behavioural adaptations that let them maintain a body temperature higher than that of their environment. • For example, you may have observed a lizard basking in the sun, which raises its body temperature and so increases its metabolic rate. • This permits the lizard to hunt actively for food. When the body of a reptile is cold, its metabolic rate is low and the animal tends to be sluggish. • Ectothermy may explain why reptiles are more successful in warm than in cold climates.

6. Ectothermic; many thermoregulate behaviourally • Metanephric kidney (paired); uric acid main nitrogenous waste • Nervous system with optic lobes on dorsal side of brain; 12 pairs of cranial nerves in addition to nervus terminalis; enlarged cerebrum • Sexes separate; fertilization internal; copulatory organ a penis, hemipenes, or rarely absent • Eggs covered with calcareous or leathery shells; extra embryonic membranes (amnion, chorion, yolk sac, • and allantois) present during embryonic life; no aquatic larval stages

7. Body covered with keratinized epidermal scales and sometimes bony dermal plates; integument with few glands • Two paired limbs, usually with five toes, and adapted for climbing, running, or paddling; limbs vestigial or absent in snakes and some lizards • Skeleton well ossified; ribs with sternum (sternum absent in snakes) forming a complete thoracic basket; skull with oneoccipital condyle • Respiration primarily by lungs, which have high surface area and filled by aspiration; no gills; cloaca, pharynx, or skin used for respiration by some

8. Order Squamata: Lizards and Snakes • Squamates are the most recent and diverse products of diapsid evolution, comprising approximately 95% of all known living nonavian reptiles. • .Skulls of squamates are modified from the ancestral diapsid condition by loss of dermal bone ventral and posterior to the lower temporal opening. • This modification has allowed evolution in most lizards and snakes of a mobile skull having movable joints. • Such a skull is called a kinetic skull. • The quadrate, which in other reptiles is fused to the skull, has a joint at its dorsal end, as well as its usual articulation with the lower jaw. • In addition, joints in the palate and across the roof of the skull allow the snout to be tilted upward .

9. Suborder Sauria: Lizards • Lizards are an extremely diverse group, including terrestrial, burrowing, aquatic, arboreal, and aerial members. • Among the more familiar groups in this varied suborder are geckos (Gekkonidae) small, agile, mostly nocturnal forms with adhesive toe pads that enable them to walk upside down and on vertical surfaces; iguanids (Iguanidae), including most familiar New World lizards, often brightly coloured with ornamental crests.

10. Suborder Serpentes: Snakes • Snakes are limbless and usually lack both pectoral and pelvic girdles (the latter persists as a vestige in pythons, boas, and some other snakes). • The numerous vertebrae of snakes, shorter and wider than those of tetrapods, permit quick lateral undulations through grass and over rough terrain. • Ribs increase rigidity of the vertebral column, providing more resistance to lateral stresses.

11. Traditionally, the order Squamates was divided into three suborders: Sauria (or Lacertilia) (lizards), Serpentes (snakes) & Amphisbaenia (amphisbaenians). • .Because of the limited kinesis of lizard skulls, they are able to consume only relatively small food items. • In contrast, the highly kinetic skull and feeding apparatus of snakes, which enable them to eat prey several times their own diameter, are remarkable specializations, which may be responsible for their incredible success.

12. Order Chelonia / Testudinata: Turtles • Body short, broad and oval • Limbs clawed and or webbed, paddle-like • Body encased in a firm shell of dorsal carapace • Thoracic vertebrae and ribs usualy fused to form carapace • Jaws with horny sheaths • No sternum, no teeth • Heart incompletely 4-chambered with a partly divided ventricle eg Tortoise, Turtles

13. Turtles have protective shells • Members of order Testudines are enclosed in a protective shell made of bony plates overlaid by horny scales. • Some terrestrial species can withdraw their heads and legs completely into their shells. • Turtles do not have teeth. Their horny beak covers the jaws. • The size of adult turtles ranges in length from about 8 cm to more than 2 m (6.5 ft) in the great marine species, which may weigh 450 kg. • The forelimbs of marine turtles are modified into flippers. • Biologists usually refer to the aquatic forms as turtles and to the land species as tortoises. Freshwater types are sometimes called terrapins.

15. Body divided into head , trunk and tail • Have elongate body, long tail well developed clawed pentadactyl limb adapted for running, climbing, and digging. • Skin is usually covered with scales • The skull of snakes is even more kinetic than that of lizards. Such exceptional skull mobility is considered a major factor in diversification of lizards and snakes.

17. A large male marine iguana, Amblyrhynchus cristatus, of the Galápagos Islands, feeding underwater on algae. This is the only marine lizard in the world. It has special salt-removing glands in the eye orbits and long claws that enable it to cling to the bottom while feeding on small red and green algae, its principal diet. It may dive to depths exceeding 10 m (33 feet) and remain submerged more than 30 minutes. Amblyrhynchus

18. Males are strongly vocal (to announce territory and to discourage approach of other males) and they must, of course, hear their own vocalizations. • Other species of lizards vocalize in defensive behaviour. • Many lizards live in the world’s hot and arid regions. • Since their skin lacks glands, water loss by this avenue is much

19. Found in field, garden • Diurnal of seen during the day • Often lives in crevices, holes • Can run swiftly on the ground

20. Scales and claws form the exoskeleton • Scales form a continuous cover over the body • Sensory devices in the form of bristles are present on the body called prototrichus

21. Gas exchange takes place through their lungs • Reptilian lungs are better developed than the saclike lungs of amphibians. • Divided into many chambers, the reptilian lung provides a greatly increased surface area for gas exchange. • Most reptiles have a three-chambered heart that is more efficient than the amphibian heart. • The single ventricle has a partition, though incomplete, that separates oxygen-rich and oxygen-poor blood, facilitating oxygenation of body tissues. • In crocodiles the partition is complete, and the heart has four chambers

22. Majority are carnivorous feeding largely on insects • Their paired limbs, usually with five toes, are well adapted for running and climbing in search of prey. • In addition, their well-developed sense organs enable them to locate prey quickly

23. Digestive system consist of the Mouth, buccal cavity, Pharynx, oesophagus, stomach, small and large intestine. • The entire system is held in position with the hel of folds of peritoneum • Stomach is attached with the body wall with the help of mesogaster, the ileum by mesentery and retrum by mesorchium.

24. Running, • Climbing, with the aid of the four limbs • During this process the tail can fall off but will regenerate later

25. Circulatory system functionally divided into pulmonary and systemic circuits; heart typically consisting of a sinus venosus, an atrium completely divided into two chambers, and a ventricle incompletely divided into three chambers; crocodilians with a sinus venosus, two atria, and two ventricles

26. Consist of 2 metanephric kidnesy which are elongated, dark-red, flattened and lobed lying on posterior region of abdominal cavity attached to the dorsal wall

27. There is sexual dimorphism, female lay eggs • However, sperm cannot penetrate this shell. Fertilization must take place within the body of the female before the shell is added. • In this process, the male uses a copulatory organ (penis) to transfer sperm into the female reproductive tract. An amnion surrounds the embryo as it develops within the protective shell. • The hard, dry, horny scales that retard drying are another • adaptation to life on land.. • Eggs are protected by thin shells with little lime