Ch. 41 - Reptiles

1. Ch. 41 - Reptiles • Unlike amphibians, reptiles don’t have to return to the water to reproduce. They were the first vertebrates to live on land during their whole life cycle. • Reptiles evolved a new reproductive structure that allowed them to reproduce on land. What is this structure? • Amniote egg • Video

2. Amniote Egg ( 5 parts) • 1. Porous shell – protects & prevents water loss. • 2. Amnion – salty fluid that allows the embryo to float. • 3. Allantois – excretes nitrogenous waste from the embryo • 4. Chorion – lines the outer shell. Diffuses carbon dioxide & oxygen through the shell. • 5. Yolk sac – supplies food for the embryo.

3. Characteristics of Reptiles • 1. Dry body covering (some with scales) • Made of keratin to prevent water loss. • 2. Lungs • 3. 3-chambered heart with the ventricle partially divided. (alligators have 4) • 4. Ectotherms – body temperature is influenced by the environment. • 5. Limbs, if present, have toes with claws. • 6. Internal Fertilization (big advantage) • Video

4. Origin of Reptiles • Reptiles were thought to of arose from the cotylosaurs. Pg. 841 • Mesozoic era is known as the Age of Reptiles. • When were the dinosaurs thought to have become extinct? • Cretaceous Period • Dinosaur means “terrible lizard”

5. Reptile Orders  Cl.: Reptilia • 1. Rhynochocephalia • Tuatara – the only species in this order • Only in New Zealand • Parietal eye – “3rd eye” on the top of their head

6. 2. Chelonia  Turtles • Dorsal shell is called the carapace • Ventral shell is called the plastron • A bridge connects the two. • Turtles are protected very well with their shell. • Snapping turtles are one of the more aggressive turtles. They have a worm-like tongue to attract fish. • Video

7. 3. Crocodilia • Crocodiles & alligators • Caimans (short & wide snout) & gavials (long & narrow snout). • The only living relatives of the dinosaurs. • Have you ever wondered why an alligator or crocodile doesn’t swallow a lot of water when it has its mouth open? • It has a glottis that prevents this. • Have you ever heard of the “Crocodile Man”? • Video

8. 4. Squamata  Largest Order • Lizards & Snakes • There are only 2 poisonous lizards • 1. Gila Monster – S.W. U.S. • Has grooved teeth with venom & shakes its head to release the venom. • 2. Beaded Lizard – Western Mexico • Name as many lizards a possible • Iguanas, horned toads, chameleons, skinks, & geckos • Video

9. Horned lizards or horny toads live around here. They have armored spikes covering them and when disturbed they hiss and squirt blood out their eyelids. • Skinks and geckos have the ability to lose their tails and regenerate a new one. • The term for this is autotomy. • Video

10. Snakes • No limbs and no external ears • There is evidence for believing that snakes once had legs. Some pythons & boas still have vestigial hind legs. • How many of you fear snakes? • How many of you fear rattlesnakes? • A graduate study was done on the human perception of snakes. • Video

11. 2,800 species of snakes, only 300 species are poisonous or dangerous. • What are the poisonous snakes of Kansas? • Prairie rattlesnake, pigmy rattlesnake, cottonmouth, western diamondback rattlesnake, timber rattlesnake, copperhead. • Video • What is the largest snake in the world? • Anaconda (33 ft.), smallest is about 4 in. • What does molting mean? • Snakes have between 100 – 400 vertebrae

13. 3 ways of movement in snakes • 1. Lateral Undulation – most common method for crawling or swimming. • Draw • 2. Rectilinear or caterpillar movement – is the contract and condense of the muscles. • Draw • 3. Sidewinding – mostly used by??? • Draw

14. Snake Parts • Nictitating membrane to cover their eyes. • Forked tongue that is used for the great sense of smell. • The branches of their tongue pick up particles in the air, then slide over top their Jacobson’s organs at the roof of their mouth, which are sensitive to odors. • All snakes are carnivores • A snake’s jaw can unhinge to engulf their prey. • Video

15. What are the 2 methods snakes use to kill its prey? • 3 methods of injecting venom: • 1. Vipers – large front fangs (hypodermic) • Ex. Rattlesnake, copperheads, cottonmouth • 2. Elapids – small front fangs (hypodermic) • Ex. Cobra & coral snakes

16. 3. Rear-fanged snakes – bite the prey & use grooved back teeth to inject the venom. • Twig snakes & boom slang snakes of Africa

17. 2 types of poisons in venom • 1. Neurotoxins – affects the nervous system • Can’t breath or swallow • 2. Hemotoxins – affects the circulatory system • Destroys the blood vessels (rupture) • Some snakes use pits to detect heat from warm-blooded mammals. (pg. 836) • Name the snake that can eat a rattlesnake? • King snake

18. Reproduction • Internal Fertilization • Oviparous – lays the eggs outside her body. • Ovoviviparous – eggs are hatched inside her body. Not nourished • Viviparous – bear live young that are nourished inside her body until they are developed. • A snake breaks through the shell by using an egg tooth, which is lost after it breaks through the egg.