1. Reptiles
Section 31.1

2. Animal Classification
Order Squamata
Snakes and lizards
Order Crocodilia
Crocs and gators
Order Testudines 
(or Chelonia)
Turtles and tortoises
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
Invertebrates
Animals
Fishes
Amphibians
Ectotherms
(cold-blooded)
Vertebrates
Reptiles
Phylum Chordata
Birds
Mammals
Endotherms
(warm-blooded)

3. What is a Reptile?
Class Reptilia – snakes, turtles, alligators, and lizards
Stem reptiles – early reptiles that were the first animals to become adapted to life on land
Evolutionary advantages reptiles have over amphibians
Claws
Dry skin (scales)

4. Scaly Skin
Unlike the moist, thin skin of amphibians, reptiles have a dry, thick skin covered with scales
Scaly skin prevents the loss of body moisture and provides additional protection from predators

5. Scaly Skin
Because of their thick skin, reptiles are dependent on lungs as their primary organ of gas exchange
Desert Horned Lizard

6. Reproduction Most reptiles reproduce by laying eggs on land
Some snakes give live birth to well-developed young
Gartner snake giving birth
Sea turtle eggs

7. Anaconda Birth

8. Reproduction
Amniotic egg – provides nourishment to the embryo and contains membranes that protect it while it develops in a terrestrial (land) environment
The egg functions as the embryo’s total life-support system

9. Reproduction Parts of an amniotic egg
1. Amnion – a membrane filled with fluid that surrounds the developing embryo; it cushions the embryo and prevents dehydration

10. Reproduction
2. Shell – The reptile egg is enclosed in a leathery shell

11. Reproduction
3. Yolk – The main food supply for the embryo; its enclosed in a sac that is also attached to the embryo

12. Reproduction
4. Albumen – the clear part of the egg; a source of additional food and water for the developing embryo

13. Reproduction
5. Allantois – a membranous sac that stores the embryo’s wastes

14. Reproduction
6. Chorion – a membrane that forms around the yolk, allantois, amnion, and embryo; the chorion and the allantois allow gas exchange for respiration

15. Reproduction
7. Egg tooth – A reptile hatches by breaking its shell with the horny tooth on its snout; it falls off after hatching

16. Reproduction All reptiles have internal fertilization
Snakes and lizards have hemipenes
Hemipenis – structure used to inject sperm into a female
Cloaca – opening where the hemipenes is inserted; waste also exits the cloaca

17. Reproduction Embryos develop after egg is laid
Most reptiles provide no care for hatchlings, but female crocodiles guard their nests

18. Reproduction
Most reptiles lay their eggs under rocks, bark, and grasses; a few dig holes or form a nest
In crocodilian species, both low and high temperatures result in females and intermediate temperatures select for males

19. Reproduction
In many turtle species, eggs from cooler nests hatch as all males, and eggs from warmer nests hatch as all females

20. Skeletal Changes in Reptiles
Reptiles have legs that are placed more directly under the body rather than at right angles to the body as in amphibians
This makes walking and running easier

21. Circulatory System
Most reptiles, like amphibians, have three-chambered hearts
Crocodilians have four chambered hearts that completely separates oxygen-rich blood from oxygen-poor blood

22. Circulatory System
This separation supports the higher level of energy use required by land animals

23. Ectotherms Reptiles do not inhabit extremely cold regions
Many species of reptiles become dormant during cold periods in moderately cold environments (northern United States)

24. How Reptiles Obtain Food
Most turtles and tortoises are herbivores, and those that are predators prey on worms and mollusks

25. How Reptiles Obtain Food
Snapping turtles are extremely aggressive, attacking fishes and amphibians, and even pulling ducklings under water

26. How Reptiles Obtain Food
Lizards primarily eat insects
The Komodo dragon, the largest lizard, is found on several islands in north of Australia (Indonesia)

27. How Reptiles Obtain Food
The komodo dragon is an efficient predator, sometimes even of humans
Mouth is filled with deadly bacteria that is used to kill prey

28. How Reptiles Obtain Food
Some snakes have poisonous fangs
A constrictor wraps its body around its prey

29. Cobra vs Rat Snake

30. Sense Organs
Pit organs – heat-sensitive areas that enable snakes to detect air temperature brought by the presence of warm-blooded animals

31. Sense Organs The tongue is used for smelling
Jacobson’s organ – a pitlike sense organ on the roof of the mouth that picks up and analyzes airborne chemicals

32. Turtles Order Testudines (or Chelonia)
The dorsal part of the shell is the carapace, and the ventral part is the plastron
The vertebrae and expanded ribs of turtles are fused to the inside of the carapace

33. Turtles
Most turtles can draw their limbs, tail, and head into their shells for protection against predators
Turtles have powerful jaws with a beaklike structure that is used to crush food

34. Turtles Tortoises Aquatic Eat insects and worms (some eat birds)
Have claws
Webbed feet
Can live up to 60 years
Tortoises
Terrestrial
Eat fruits and insects
Do not have claws
Feet are not webbed; they’re round and stumpy
Can live up to 150 years

35. Crocodiles Order Crocodilia Crocodiles Alligators
Long, slender, V-shaped snouts,
Light olive brown coloration
Found in saltwater and estuaries
Estuary – a mixture of freshwater and saltwater
Alligators
Short, broad, U-shaped snouts
Blackish coloration
Found in freshwater

36. Pictures of croc and gator

37. Crocodiles
Crocs and gators both have powerful jaws that can drag prey underwater and hold it there until it drowns

38. Crocodiles Both lay eggs in nests on the ground
Unlike other reptiles, these animals stay close to their nests and guard them

39. Tiger vs. Crocs

40. Lizards and Snakes Order Squamata Most lizards have four limbs
Snakes have no limbs and lack the bones to support limbs
Exception are pythons and boas which retain bones of the pelvis
The claw is known as a spur

41. Lizards and Snakes Some snakes even swim and climb trees
Have ridges on its belly used for gripping
(like tire treads gripping the road)

42. Lizards and Snakes Snakes usually kill their prey in one of three ways
1. Constriction – snakes wrap themselves around their prey
Examples: boas, phythons, and anacondas
Boa

43. Lizards and Snakes
2. Venom – These snakes use poison to paralyze or kill their prey
Rattlesnakes, cobras, and vipers

44. Lizards and Snakes
3. Non-poisonous and non-constricting snakes get their food by grabbing it with their mouths and swallowing it whole

45. Bull Snake vs. Ground Squirrel

46. Cobra vs. Mongoose

47. Cat vs. Snake