Chapter 31-1By: Swetha Ramamurthy

Katharine WeiPeriod 3!

A reptile is…

0a vertebrate that has dry, scaly skin, lungs, and terrestrial eggs with several membranes.

0These characteristics enable reptiles to live their entire lives out of water.

Evolution of Reptiles

0Reptiles were the first to reproduce by not depositing eggs into water.

0Mammal-like Reptiles – roamed the Earth by the end of the Pemian Period (about 245 million years ago). They displayed a mix of reptilian and mammal-like characteristics.

0Dinosaurs – became dominant in Triassic Period. During the late Triassic and Jurassic period, a great adaptive radiation took place. This is why the Mesozoic Era is called “the Age of Reptiles”. Dinosaurs were everywhere, ranged in size, shape, and any other physical trait. They all belonged to either the Ornithischia “bird-hipped dinosaurs” or the Saurischia “lizard-hipped dinosaurs”.

0Extinction – at the end of the Cretaceous Period, about 65 million years ago, a mass extinction occurred worldwide.

Functions

0Can control their body temperature 0Ectotherms: warm their bodies up using the sun, cool

down using water or underground burrows0Wide variety of methods of feeding0 Iguanas: herbivores, have long digestive systems to

digest food0Snakes and others: carnivores, swallow food whole0Most reptiles eat insects, chameleons have a very long

tongue to grab insects

Respiration

0Reptiles have well-developed lungs because of spongy quality- provides more gas-exchange area; cannot respire through skin

0Some have muscles on their ribs to expand and collapse the chest cavity while breathing

0Some crocodiles have flaps of skin to separate the mouth from the nasal passage, so they can breathe through nostrils while the mouth is open

Circulation

0Double-loop circulatory system-One loop: blood goes to and from lungs-Other loop: blood goes to and from rest of the

body0Heart has 2 atria, most have 1 ventricle with a partial

septum-Partial septum: wall separates rich and poor

oxygen blood0Crocodiles and alligators have 2 atria and 2 ventricle

Excretion

0Water-conserving excretory system, cloaca absorbs excess water

0Urine flows from kidney to cloaca in some reptiles while in others it flows from storage in urinary bladder to cloaca

0Water reptiles’ urine has ammonia, because the large amount of water can dilute the poison in it

0Land reptiles convert the ammonia in their urine to less toxic uric acid

Response

0 Reptiles have a pair of sensory organs besides their nostrils that detect chemicals when reptiles flick their tongues

0 External eardrums and one bone takes sound to inner ear0 Snakes can pick up vibrations in the ground through a

bone in their skull, and even detect body heat of prey or predator

0 Movement: Large, strong limbs that make reptiles with legs move fast

0 Flexible, carries more body weight

Reproduction

0 Internal fertilization: sperm inside female body0Oviparous: develop outside mother’s body0Amniotic egg: develop without drying out0Shell and 4 membranes surrounding embryo

-amnion: cushions embryo-yolk sac: provides nutrients for embryo-chorion: regulates transport of oxygen and

carbon dioxide from surface of egg to embryo-allantois: stores waste

Groups of Reptiles

0Lizards and Snakes: order: Squamata (scaly)0Lizards have legs, clawed toes, external ears, movable

eyelids0Snakes are legless, large predators, vary greatly in

size, some produce venom0Crocodilians: order: Crocodilia (alligators, crocodiles,

caimans and gavials0 Fierce carnivores, broad snout, protective of young,

0Turtles and Tortoises: order: Testudines-Turtle: aquatic, Tortoises: terrestrial, Terrapin: salt

water0Shell in skeleton, shell has carapace (dorsal), plastron

(ventral)Backbone is center of carapace, pull into shells for protection0Large variety of habitats, not teeth only jaws, strong limbs0Tuataras: last of order: Sphedonta0Resemble lizards but no external ears, have scales0Has 3rd eye on top of brain, senses level of sunlight0Reptiles are in danger from human activities (hunting),

conservation efforts are needed