Transcript Reptiles
Reptiles The First True Terrestrial Tetrapods # of Species of Reptiles Species Numbers by Higher Taxa: Amphisbaenia (amphisbaenians) 165 Sauria (lizards) 4765 Serpentes (snakes) 2978 Testudines (turtles) 307 Crocodylia (crocodiles) 23 Rhynchocephalia (tuataras) 2 Reptiles total 8240 Reptile Characteristics • • • • • • • • • Ectothermic Dry skin covered in scales Most have 2 pairs of short legs & clawed feet Oviparous reproduction (Internal fertilization – to avoid desiccation of gametes) Eggs have a leathery shell and yolk (amniotic) Lungs to breathe 3 or 4 chambered heart No metamorphosis (young look like miniature parent) Hibernate & aestivate Ectothermy – Body temperature regulated by ambient air temperature Dry Scaly Skin The body of reptiles is covered with horny epidermal scales to reduce water loss and provide protection. Reptile Legs • Short tetrapods for walking • Positioning of the legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs. Paired Limbs • The paired limbs usually have five toes and are variously adapted for: • Swimming • Running • Climbing • (Absent altogether in the snakes) Oviparous • Amniotic eggs have a leathery shell to prevent desiccation Amniotic Egg Amniotic Egg Structures & Functions • Chorion provides a special hard covering that is permeable to respiratory gases (O2 and CO2) while being impermeable to water vapor. • Allantois is a storage reservoir for metabolic waste products such as nitrogenous compounds. • Amnion is a fluid filled sac that acts as a cushion for the embryo and also prevents desiccation. • Yolk sac contains food for the embryo, thus eliminating the need for a larval stage. Reptile Lungs • Respiration is no longer through the skin, but only through internally protected and moistened lungs. • They have a much greater surface area for the exchange of gases. • They are inflated and deflated by the expansion & contraction of the rib cage. Reptile Hearts • Reptiles have a 3-chambered heart • Crocodiles have a 4-chambered heart Excretory Waste • The excretory waste of the reptiles is uric acid unlike the dilute, water wasting ammonia in the urine of Amphibians. Family Amphisbaenidae (Worm Lizards) • Size: The total body length ranges from 10 cm to about 70 cm. • Distribution: Mostly Africa & South America with a few species in Europe and North America. • Habitat: Soil. • Reproduction: usually oviparous, but some are live-bearing Lizard Anatomy Lizard Reproduction Hatchling Komodo Dragon Snake Anatomy Jacobson’s Organ Snake Reproduction Turtle Anatomy Turtle Shell Anatomy Turtle Shell Anatomy Fusion of ribs, vertebrae, & carapace Turtle Life Cycle Turtle Reproduction Crocodilians • Crocodiles, Alligators, Caimans, & Gavials Gavial Alligator Crocodile Caiman • The temperature inside the nest of several crocodilian species decides the sex of the young. ~50-80 eggs • If the nest temperature is 30ºC, females will hatch from all the eggs • If the temperature is above 34ºC, all will be males. • If the temperature is in between, there will be young of both sexes. Crocodilian Reproduction