Reptiles

Section 31.1

Animal Classification

Animals

Invertebrates

Vertebrates

SpongesCnidariansWormsMollusksArthropodsEchinoderms

Ectotherms(cold-blooded)

Endotherms(warm-blooded)

FishesAmphibians

BirdsMammals

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

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)

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 eggsGartner snake giving birth

Anaconda Birth

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

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; its 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

Hemipenis – structure used to inject sperm into a female

Cloaca – opening where the hemipenes is inserted; waste also exits the cloaca

Reproduction

Embryos develop after egg is laid Most reptiles provide no care for hatchlings,

but female crocodiles guard their nests

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

Reproduction

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

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

Crocodilians 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)

How Reptiles Obtain Food

Most turtles and tortoises are herbivores, and those that are predators prey on worms and mollusks

How Reptiles Obtain Food

Snapping turtles are extremely aggressive, attacking fishes and amphibians, and even pulling ducklings under water

How Reptiles Obtain Food

Lizards primarily eat insects The Komodo dragon, the largest lizard, is

found on several islands in north of Australia (Indonesia)

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

How Reptiles Obtain Food

Some snakes have poisonous fangs A constrictor wraps its body around its prey

Cobra vs Rat Snake

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 pitlike 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

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

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

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

Crocodiles

Both lay eggs in nests on the ground Unlike other reptiles, these animals stay

close to their nests and guard them

Tiger vs. Crocs

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, phythons, 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

Bull Snake vs. Ground Squirrel

Cobra vs. Mongoose

Cat vs. Snake