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 –
–

Lizards –
–

Carnivores
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 heatsensitive 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
–
–
Constrictors – wrap body around prey
–
–
Examples: rattlesnakes, cobras, vipers
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.