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Chapter 18
Reptiles and Amphibians
Cold-blooded Animals
• Reptiles are considered cold-blooded
animals.
• Their body temperature fluctuates with the
temperature of their surroundings.
• Scientifically this is known as
poikilotherms.
Similarities among Reptiles
• All true reptiles are vertebrates
• All are cold-blooded
• All have tough, dry skin which is covered in
scales.
• Most molt several times a year
• All (except snakes) are tetrapods
• Each has claws
• Most are oviparous
• Some are ovoviviparous – eggs are kept inside
the female and then the babies hatch and are
“born” alive.
Lizards:
The most numerous Reptiles
• Lizards are a “squamate”
• Lizards have eyelids (snakes do not)
Lizards:
The most numerous Reptiles
• Various habitats – lizards
are most numerous in
tropical habitats
• Varying sizes – majority
are less than a foot long
• Poisonous lizards – only
two species in North and
Central America are
poisonous – the Gila
monster and the Mexican
beaded lizard.
Lizards:
The most numerous Reptiles
• Some lizards have tails that detach that enables
them to escape from predators.
• Other defense mechanisms:
- chuckwallas inflate their bodies in crevices.
- some can glide from tree to tree
- frilled lizards make themselves look scary to
predators
- horned lizards (we have these) have prickly
“horns” on them…they also squirt blood out of
their eyes.
Lizards:
Eating Habits
• Most lizards are insectivores…
• Some lizards are herbivores – ex: the
chuckwalla
Snakes:
the most widespread reptiles
• Snakes are legless vertebrates
• Snakes are not found in artic regions –
because they cannot survive freezing
temperatures.
• To survive cold temperatures elsewhere,
they “hibernate” by burrowing into the
ground.
Snakes
• Snakes come in varying sizes:
the blind snake is only 5 to 6
inches
the python and anaconda are the
largest, growing to 30 feet and 300 pounds
the longest snake in North
America is the indigo snake that can grow
to 9 feet in length
Snakes:
Methods of Locomotion
1. Lateral undulation: a majority of snakes move
by this – the snake bends into a series of
curves as it keeps its body flat on the ground.
2. Reticular movement: thick bodies snakes –
move in a straight line – some use this to climb
trees
3. Concertina movement – the front part of the
body moves forward and the then pulls the
back portion up to it.
4. Sidewinding movement – the snake move
sideways – they lift their body off the ground as
they move.
Snakes
• Snakes have a scaly skin
• As the dead cells reach the surface, they
form a tough layer.
• When the outer skin becomes worn or thin
or too small, it is shed
Snakes:
Sense organs
• Scale covered eyes – most snakes are
nearsighted – they can see movement, but
cannot differentiate between objects.
• Hearing without ears – they have no external ear
opening – they do have an inner ear- they
cannot hear high pitched sounds
they use their lower jaw (attached to a
quadrate bone) to transmit sounds to their ear
membrane (much like birds)
Snakes:
Sense organs
• Sense of smell – the snake has nostrils,
but its primary sense of smell is its tongue
• The snake flicks out its tongue and picks
up smell particles that it sends to the
Jacobson’s organ where nerve endings
decipher the smell.
Snakes:
Design for Feeding
Double hinged jaw:
The snakes jaw comes undone
and the snake is able to consume large
prey.
Engulfing a Meal:
Snakes eat their prey whole.
Snakes
Groups of snakes:
Blind snakes – smallest snake – often
mistaken for worms
Constrictors – kill their prey by “constricting”
their prey – includes pythons, boas, and anaconda
Colubrids – 2/3 of all snakes – they can be
terrestrial, aquatic, or arboreal – includes garter snakes,
water snakes, king snakes, and racers.
Majority are harmless – but, a group of
them do have fangs, but the fangs are in the back of the
mouth – so they rarely bite a human.
Snakes
Groups of snakes:
Elapids – all are poisonous – fangs in
the front of the mouth – over half of all elapids
live in Australia – also includes cobras
the king cobra is the largest
venomous snake
also includes mambas – highly
aggressive snake
in the us, we have the coral
snake
sea snakes are also elapids
Snakes
Groups of snakes:
Vipers – Most are viperids, which
means they have fangs that retract beck
into a fold of skin.
pit vipers – have heat sensor
that allows them to “see” an object
examples in the us:
cottonmouth (highly aggressive),
copperheads, and rattlesnakes.
Snake Venom
Of the 2700 species of snakes, only 250 are
venomous…
There are two types of toxins in snake venom:
1. neurotoxin: nerve poison – affects the
nervous system, shutting down the heart lungs
and muscles.
2. hemotoxin: blood poison – damages blood
vessels and destroys red blood cells.
Snakebite Treatment
Only 8-12 snakes bites are fatal in the U.S. each
year…
Use of antitoxin (antivenin) has decreased the
death rate worldwide…
Keep the person calm and the limb lower than the
heart to slow the motion of the poison…
NEVER attempt to “suck” the venom out with your
mouth…you may infect yourself!
Turtles
• Turtles: the only
reptile with a shell…
• The upper shell is
called a carapace.
• The lower shell is the
plastron.
Characteristics of Turtles
• 50 species live in the U.S. of the 240
species worldwide..
• Turtles hibernate in the cold winters.
• Some use estivation to survive dry
periods.
• They are toothless.
Freshwater Turtles
• Includes the box turtle, which is no longer
sold as a pet due to the salmonella that it
carries.
• Snapping turtle
Salt Water Turtles
• The largest living
turtles…
• They lay their eggs on
the sand of beaches,
but do not care for the
young…
Tortoises
• Land turtles
• The longest living
animal – the giant
turtle on the
Galapagos island –
150 years old
Our Mojave Desert
tortoise…
Crocodilians
• The largest living
reptiles.
Characteristics of Crocodilians
• Have partially webbed feet for moving through
water
• Powerful tails
• All crocodilians are carnivorous
• They include salt water crocodiles, alligators,
caimans
• Oviparous – but they tend the nest unlike other
reptiles
• Nile crocodiles (the largest) can grow to 20 feet
long
• There are fossils of extinct crocs that were 40
feet long
Tuataras:
Spiny-crested Reptiles
• Inhabits New Zealand
• It has a third “eye” – called a parietal eye –
situated on top of its brain
• The “eye” senses radiation
• It is insectivorous
Amphibians
• Live in both the land and water
• Includes frogs and toads
Characteristics of Amphibians
• Most are oviparous – eggs can attach
anywhere
• Usually pass through an aquatic, gilled
larval stage
• All have a three chambered heart
• Some estivate by burrowing into the soil to
avoid drying out and heat
Frogs and Toads:
Leaping Amphibians
• Frogs have smooth skin
• Toads have rough “warty” skin
• Protective covering
• Toxic skin secretions – one ounce of the
arrow-poison frog can kill 3 million people
• External fertilization – female lays the
eggs and then the male fertilizes them
Anatomy of an Amphibian
• Features of the head
- Protruding eyes
- nictitating membranes – transparent inner
eyelids
• Features of the oral cavity
- tongue is attached in front
- maxillary teeth – project from upper jaw –
are called vomerine teeth because they
extend from bones of the skull
- Frog swallows by pushing food with its
eyeballs
Anatomy of an Amphibian
• Digestive system
- swallow prey whole
- “fat bodies”, above the kidneys keep frog
alive during periods of estivation and
hibernation
• Respiratory system
- frog can breath through tiny capillaries in
mouth
- under water the frog can “breath” in the
water through its skin
Anatomy of an Amphibian
• The circulatory system
- three chambered heart
Other Amphibians
Salamanders – amphibians with tails
- some salamanders have no lungs or
gills – they use buccal respiration
Caecilians – limbless amphibians
- most live underground
- 7 to 52 inches long