Reptiles Section 31.1

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

What is a Reptile? Class Reptilia – snakes, turtles, alligators, and lizards Evolutionary advantages reptiles have over amphibians  Claws  Dry skin (scales)

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

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

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

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

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

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

Reproduction  3. Yolk – The main food supply for the embryo; it’s enclosed in a sac that is also attached to the embryo

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

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

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

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

Reproduction All reptiles have internal fertilization Snakes and lizards have hemipenes (plural)  Hemipenis (singular) – structure used to inject sperm into a female  Cloaca (Latin for “sewer”) – opening where the hemipenes is inserted; waste also exits the cloaca

Reproduction Embryos develop after egg is laid Most reptiles lay their eggs under rocks, bark, and grasses; a few dig holes or form a nest Most reptiles provide no care for hatchlings, but female crocodiles guard their nests

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

Circulatory System Most reptiles, like amphibians, have three- chambered hearts Crocodiles and alligators have four- chambered hearts that completely separates oxygen-rich blood from oxygen-poor blood

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

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

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

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

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

Turtles  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

Crocodiles Order Crocodilia Crocodiles  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

Pictures of croc and gator

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

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

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

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

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

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