Reptiles have several adaptations that allowed them to thrive on land, including dry, scaly skin that reduces water loss and the ability to lay shelled eggs. Reptiles are ectothermic, regulating their body temperature through external heating and cooling. They have three-chambered hearts and rely on lungs for breathing. Snakes and lizards have a flexible jaw joint that allows them to swallow large prey whole. Turtles and tortoises have protective shells, while alligators and crocodiles are the closest living relatives to dinosaurs.

1. 17.4 Reptiles Page 357

2. Reptile Adaptations Body Covering: reduced water loss Eggs: could be laid on land These adaptations appeared 300 million years ago

3. Reptile Characteristics Dry, waterproof covering made up of scales Conserve water Prevent exchange of oxygen & carbon dioxide Rely on lungs for breathing

4. Reptile Characteristics Produce eggs covered by a thick, leathery shell Prevents moisture from escaping Keeps sperm from entering

5. Reptile Characteristics 3-Chambered Hearts Partial wall inside main chamber lessons mixing of high and low oxygen blood Results in a heart that works as well as our 4-chambered

6. Reptile Heart

7. Human Heart

8. Reptile Characteristics ECTOTHERMS Good at regulating internal body temperature Bask in sun when air is cool Seek shade when too hot Maintain a steady body temperature

9. Lizards & Snakes Closely related ALL snakes & MOST lizards are carnivores Both have a special jaw hinge Allows lizards & snakes to swallow their prey whole by increasing the size of their mouths

10. Snakes Some still have hipbones & remnants of hind legs Sign they evolved from reptiles Poor hearing and eyesight Keen sense of smell & taste

11. Snake Jaw

12. Snake Tongue Tongues used to find prey and gather info about environment Tip of tongue picks up chemicals Organ in roof of mouth identifies & detects odors

15. Turtles & Tortoises ALL have shells Little has changed since appearing hundreds of millions of years ago When in danger, most pull in head, legs, and tails under shell

16. Turtle Shells Form from bony plates connected to their ribs and vertebrae Covered by layer of skin Color patterns and markings

17. Comparison Turtles Tortoises Flat, streamlined shells Ponds, lakes, rivers, or ocean Must return to land to lay eggs Dome-shaped shells Land animals Remain on land all their lives

18. Alligators & Crocodiles Closest living relatives to dinosaurs Lizard-like in shape Can grow as long as small boat Backs have large, deep scales

19. Comparison Alligators Crocodiles Broad head, rounded snout Live mostly in North America & Asia Care for their young Female protects eggs After hatching, male and female protect babies Narrow head, triangular-shaped snout Live in tropical America, Africa, Asia, & Australia