REPTILES

What is a reptile?

Snakes, turtles, alligators, and lizards are considered reptiles.

Reptiles have scaly skin Reptiles reproduce on land Reptiles are ectotherms

How Reptiles Evolved Onto Land

Skeletal changes occurred. Changes in the position of the legs made

them more underneath the body to allow for greater body support to walk and run on land.

Changes in the jaws and teeth allowed them to use other resources and niches on land.

Development of the amniotic egg.

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.

Reproduction

All reptiles have internal fertilization. In most cases, the eggs are laid after

fertilization and embryos develop after eggs are laid.

Most lay their eggs under rocks, bark, grasses, etc. But a few dig holes or collect materials for nests.

Most provide no care for the hatchlings. Only crocodiles and alligators guard nests.

Water not necessary for fertilization.

Reproduce on Land

Most reptiles reproduce by laying eggs on land. Some snakes give birth to live young.

Reptiles do not have aquatic larval stage. The development of the amniotic egg

allowed reptiles their independence from water. – Amniotic egg provides nourishment to the embryo

and contains membranes that protect it while it develops in a terrestrial environment. Prevents injury or dehydration of embryo.

Albumen

Function of the Egg Parts

Amnion – membrane filled with fluid that surrounds the developing embryo. The fluid-filled amnion cushions the embryo and prevents dehydration.

Shell – protection & gas exchange. Yolk – The main food supply for the embryo. The

clear part is the albumen which is a source of additional food and water for the embryo and protection.

Blood Vessels – gas exchange with the environment & nitrogenous waste. Transports nutrients.

Function of the Egg Parts

Allantois – Embryo’s nitrogenous wastes are excreted into the alantois & gas exchange. The allantois is left behind once it hatches.

Chorion – A membrane that forms around the yolk, allantois, amnion, and embryo. Allows for gas exchange for respiration & protection.

Egg Tooth – a retile is hatched with an egg tooth to crack the egg to break free from shell.

Egg tooth falls off in about one day!

3- chambered or 4-chambered Hearts??????

Most reptiles have three chambered hearts but some have a four-chambered heart.

Four chambered hearts in crocodiles keep oxygenated & deoxygenated blood separate. This allows for higher levels of energy production.

Ectotherms

Reptiles are similar to amphibians in one way; they are both ectotherms.

They depend on an external heat source and behavior to maintain their body temperature within the range needed to perform life functions.

So, reptiles do not inhabit extremely cold regions. If the are does get cold, many species will become dormant during cold periods.

Obtaining Food

Snakes –– Carnivores

Lizards –– Mostly insects but some herbivores

Turtles –– Some are herbivores while others will eat fish,

amphibians, and baby ducks.

Sense Organs

The heads of some snakes have heat-sensitive organs or pits that enable them to detect tiny vibrations in air temperature brought by the presence of warm-blooded animals.

Snakes and lizards have very good sense of smell. The forked tongue picks up molecules in the air and passes it by a structure called Jacobson’s organ. This will allow the molecule to be analyze and the brain figures out what it is.

Turtles

Only reptile to be protected by a shell made up of two parts.

Can draw their head, tail and limbs into the shell for protection.

No teeth but powerful jaws and a beaklike structure for crushing objects.

Some are aquatic (turtles) and some live on land (tortoises).

Most migrate to reproduce and lay eggs. Have vertebrae & ribs fused to carapace.

View: dnr.state.il.us/education/turtle/turpix.htm

Crocodiles vs. Alligator

Crocodiles have long and slender snouts while alligators are short and broad snouts.

Both have powerful jaws with sharp teeth. They drag prey under water until it drowns.

They can breathe air with mouths full of food and water. Both lay eggs in nest on the ground and stay close to their nests and guard them (unlike most reptiles).

View: http://www.alligatorfur.com/edu/gatorcroc.htm

Snakes & Lizards

Lizards live in a variety of places: on the ground, burrow, in trees, aquatic.

Primarily insect eaters Many are adapted to hot, dry climates Some species are limbless but most have 4. Snakes have no limbs and lack bones (except the

pythons and boas). Some can swim and climb trees & change colors.

View: http://www.inhs.illinois.edu/cbd/collections/amprep/ilspecies.html

Tortoises of Galapagos Islands

These are the largest tortoises in the world!

Komodo Dragon

Largest lizard. Lives on several islands of Indonesia and Northern Australia.

How Snakes Kill Prey

Snakes kill prey in one of three ways:– Venomous – use poison to paralyze or kill prey

– Examples: rattlesnakes, cobras, vipers

– Constrictors – wrap body around prey– Examples: boas, pythons, anacondas

– Neither Venomous nor constrictors – grab prey with mouths and swallow prey whole

– Most snakes are this way.

Tuataras

Found only in New Zealand Only survivors of a primitive group of reptiles,

most of which died out 100 million years ago.