Reptiles Chapter 31-1

What is a Reptile? Vertebrate Dry, scaly skin Lungs Terrestrial eggs with several membranes

Advantages of Dry, Scaly Skin –Prevents water loss Disadvantage of Dry, Scaly Skin –Does not grow when reptile grows –Must be shed

Evolution of Reptiles Developed adaptation: could lay eggs on land. First reptiles: Carboniferous Period As climate became dryer, amphibians became less successful, reptiles were able to survive better.

Mammal-like Reptiles Roamed earth 245 mya. Had mammalian and reptilian characteristics. Came to dominate many land habitats

Dinosaurs Late Triassic and Jurassic period: a great adaptive radiation of reptiles took place. Mesozoic Era: known as age of reptiles “Age of Dinosaurs" (the Mesozoic Era) included three consecutive geologic time periods –Triassic –Jurassic –Cretaceous Period

Different dinosaur species lived during each of these three periods. –Stegosaurus already had been extinct for 80 million years before the appearance of the Cretaceous dinosaur Tyrannosaurus.

Dominant Amphibians Cochleosaurus

Exit the Dinosaurs Mass extinction occurred at end of Cretaceous. Causes: natural disasters, lava flows, dropping sea levels, and huge comet smashing into Yucatan peninsula in Mexico.

Descendents of Dinos still alive today: BIRDS

Form and Function in Reptiles Body Temperature Control –Reptiles = ectothermic—rely on behavior to help them control body temperature. Bask in sun during day Stay under water at night Cool down by staying in shade or burrowing

Feeding –Eat wide range of foods –Can be herbivorous or carnivorous

Respiration –Spongy lungs; provide more gas exchange than amphibian lungs –Cannot exchange gases through skin –Most reptiles have two lungs –Some snakes have one lung

Circulation –Double loop circulatory system Loop 1: Brings blood to and from lungs Loop 2: Brings blood to and from the rest of body. *

*Most reptiles have 3- chambered hearts, crocodiles and alligators have 4-chambered hearts.

Excretion –Urine produced in kidneys –Can be stored in urinary bladder –Reptile excretes uric acid; cuts down on water loss.

Response –Well-developed eyes –Well-developed sense of smell –Sensory organs: sense vibrations –Simple ears with external eardrums

Movement –Stronger limbs than amphibians that enable walking, running, burrowing, swimming and climbing.

Reproduction –Internal fertilization –Male deposits sperm inside body of female –Most reptiles lay eggs that develop outside of body. –Reptilian eggs: amniotic eggs