Reptile Introduction

What Is a Reptile?–A reptile is a vertebrate that has dry, scaly skin, lungs, and terrestrial eggs with several membranes.–These characteristics enable reptiles to live their entire lives out of water.

•Reptilian skin is dry and covered with thick, protective scales. •This prevents the loss of body water in dry environments.•The scaly layer of skin doesn’t grow, so it must be shed periodically as the reptile increases in size.

Body Temperature Control • Reptiles are ectotherms.• Ectotherms are animals that rely on

behavior to control body temperature. • To warm up, they bask in the sun or stay

under water at night. • To cool down, they move to the shade or

take shelter in underground burrows.

Reproduction •Most reptiles are oviparous, laying eggs that

develop outside the mother’s body.• All reptiles reproduce by internal fertilization• This results in the formation of an egg

The shell and membranes protect the embryo and prevent the egg from drying out. This type of egg, an amniotic egg, is one of the most important adaptations to life on land.An amniotic egg has four membranes—the amnion, the yolk sac, the chorion, and the allantois.

Evolution of ReptilesReptiles were the first vertebrates

that were not dependent on water for reproduction.

The first reptile fossil dates back to the Carboniferous Period.

DinosaursDuring the late Triassic and Jurassic

periods, a great adaptive radiation of reptiles took place.

The Mesozoic Era is often called the Age of Reptiles.

Dinosaur structure and behavior varied:• Ranged in size from small to enormous. • Ran on two legs or on four legs. • Ate leafy plants or other animals. • Some lived in small family groups. • Some may have had feathers.

At the end of the Cretaceous, a mass extinction occurred that killed the dinosaurs as well as other plant and animal groups.

Yucatan Peninsula, Mexico The Chicxulub Crater is approximately 180 km (111 miles) in diameter and 10 km (6 miles) deep

Groups of ReptilesThe four surviving groups of reptiles are:• lizards and snakes • crocodilians• turtles and tortoises• tuatara

LizardsMost lizards have four legs and clawed toes.Most lizards have external ears and movable

eyelids.Some lizards have evolved into highly

specialized forms.

Lizards

Blue Tongue Skink

Bearded Dragon

Gecko

Chameleon

Moniter Lizards

Komodo Dragon

Horned Toads

Lizards Displaying

SnakesSnakes have no legs.Snakes have immovable eyelids and no

external ear openings.Snakes are efficient predators.

Venomous Snakes:cobras, coral snake, sea snakes …….types of venom:

neurotoxinhemotoxin

snake bite? antivenom shot

Largest Snake ever officially recorded:an Anaconda, captured & measured in 1944South America - Orinoco River37 1/2 feet! estimated to weigh nearly 600 pounds!

CrocodiliansCrocodilians have long, broad snouts and a

squat appearance. They prey on animals such as fishes, deer,

and even humans. Females guard their eggs from predators and

watch over their young after the eggs hatch.

Crocodilians live only where it is warm year-round. Alligators and caimans live only in fresh water and are found almost exclusively in North and South America. Crocodiles live in either fresh or salt water and are native to Africa, India, and Southeast Asia.

CrocodilesCrocs, Alligators, Caimens

Gharial (India) Alligator (USA) Crocodile (USA)

Turtles and TortoisesTurtles live in water.Tortoises live on land. A terrapin is a turtle that lives in water that is

somewhat salty.

Turtles and tortoises have a two-part shell built into the skeleton:

• a dorsal part (top), or carapace• a ventral part (bottom), or plastron

The head, legs, and tail emerge from holes where the carapace and plastron join. Tortoises and most turtles pull into their shells for protection.

Turtles

TuatarasTuataras are found only on a few islands off New

Zealand. They lack external ears and retain primitive scales. They have a “third eye,” which is part of a complex

organ located on top of the brain.

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