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Chapter 17 and 18 Notes,
Reptiles and Amphibians
Characteristics of Class Amphibia
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Most amphibians are tetrapods, meaning they
have four limbs, but some are limbless.
Amphibians have smooth, moist skin.
Amphibians respire by lungs, skin, and gills;
either separately or in combinations.
Amphibians have a 3-chambered heart, with
two atria and one ventricle.
Amphibians are ectotherms, meaning they
require an external source of heat.
Caecilians: Order Gymnophiona (Apoda)
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Caecilians have a long slender body that is
limbless and they live in burrows.
Caecilians live in tropical regions.
Caecilian's eyes are small and the adults are
usually completely blind.
Caecilians are carnivores that eat mostly
worms and other invertebrates.
Fertilization is internal, and eggs are usually
deposited in moist ground near the water.
Caecilians
Salamanders: Order Urodela (Caudata)
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Salamanders are tetrapod amphibians with tails.
Most of the common salamanders of North
America are less than 15 cm (6”) long.
Some are much larger, like the giant Japanese
salamander that can exceed 1.5 m (4-5 ft).
Most salamanders have four equal sized limbs set
at right angles to their body.
Salamanders are typically carnivores that prey on
worms, arthropods, and molluscs.
Salamander
Giant Japanese Salamander
Frogs and Toads: Order Anura (Salientia)
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Frogs and Toads lack tails as adults.
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All frogs and toads bear a tail in the larva stage.
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Frogs and Toads are adapted for jumping.
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The name Anura means “without a tail” and
Salientia means “jumping or leaping”.
Eggs of frogs and toads hatch into a tadpole,
having a finned tail, internal and external gills,
no legs, and tadpoles are herbivores.
Frogs and Toads
Frogs and Toads: Order Anura (Salientia)
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Adults are much different than the larval form.
After tadpoles go through metamorphosis,
frogs and toads lose their tail and gills,
develop legs, and become carnivores.
Frogs and Toads vary in size from the West
African Goliath frog (30 cm long), to some that
are less than 1 cm in length.
The Goliath frog can consume rats and ducks.
Goliath Frog
Frogs and Toads: Order Anura (Salientia)
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Frogs are found all over the world, but the
majority of them are found in tropical regions.
Those that live in colder climates, hibernate in
the winter. Some frogs hibernate in the soft
mud of pools and streams.
Terrestrial frogs, such as tree frogs, hibernate in
the humus of the forest floor.
Some can even withstand freezing
temperatures by accumulating glucose and
glycogen which prevents ice-crystal formation.
Class Reptilia
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Body is covered in scales made of keratin.
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Most are tetrapods, some are limbless.
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Respiration is by lungs, not by skin or gills.
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3-chambered heart in most, with the exception of the
crocodilians which are 4-chambered.
Ectothermic; body temperature is modified by
behavioral thermoregulation.
Sexes separate; fertilization is internal
Eggs covered with leathery shells with internal
embryonic membranes.
Characteristics of Reptiles
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Reptile scales are different than fish scales.
The scales on a reptile are made of keratin and
are similar in material to mammal skin, with an
epidermis and dermis. Fish scales are more
similar to bone or teeth material.
Reptile eggs are amniotic, meaning they have
internal membranes, like the chorion and
allantois, which help exchange gases and
metabolic waste products. The tough leathery
shell also allows them to be laid in dry terrestrial
environments, unlike fish and amphibian eggs.
Reptile Scales
Amniotic Egg of a Reptile
Characteristics of Reptiles
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Reptiles have a double pump circulation with
systemic (deoxygenated) and pulmonary
(oxygenated) circulation similar to mammals.
Reptiles do not have completely separated
ventricles, which causes partial mixing of
deoxygenated and oxygenated blood.
Reptilian lungs are more efficient than
amphibian lungs because their rib cage can
expand and contract, although they lack a
muscular diaphragm like mammals.
Circulatory System of Amphibians
Circulatory System of Reptiles
Circulatory System in other
Vertebrates as a Comparison
Turtles: Order Testudinata
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The body of a turtle is enclosed in two shells;
the dorsal shell called the carapace and the
ventral shell called the plastron. The carapace
is fused with the ribs and the vertebrae.
Shell provides protection for the head, arms,
and legs, which can be retracted into the shell.
The turtle cannot expand the chest to breath so
they use abdominal and pectoral muscles to
draw air into the lungs.
Turtle Skeleton
Turtles: Order Testudinata
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Turtles lack teeth, but have beak-like jaws lined with
tough plates made of keratin.
Turtles are almost completely deaf, but they have a
good sense of smell and vision.
Turtles are oviparous, with internal fertilization.
All turtles, including marine forms bury their amniotic
eggs in the ground.
Nest temperatures determine the sex of the turtles;
low temperatures males, high temperatures females.
Turtles: Order Testudinata
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Leatherback marine turtles can reach 2 meters
in length and weigh up to 725 kg (about as
heavy as a large moose at 1500 lbs)
Some land tortoises like the Galapagos Island
tortoises can weigh several hundred kilograms.
Most tortoises are slow moving, moving only a
few hundred meters per hour.
Their low metabolism may explain their
longevity. Some living over 150 years.
Leatherback Sea Turtle
Galapagos Island Tortoise
Order Squamata: Lizards and Snakes
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About 95% of all known living reptiles.
One feature of order squamata that has made
them some of the most successful of all the
reptiles is the kinetic skull.
The kinetic skull is an adaptation of order
squamata that allows the snout to be tilted
upward, in order to capture and manipulate their
prey and increase the force of the jaws.
The Kinetic Skull
Lizards: Suborder Sauria
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Includes geckos, iguanas, skinks, and chameleons.
Most lizards are tetrapods, except the glass lizards
which are limbless.
Lizards have movable eyelids, snakes do not.
Lizards have rods and cones in their eyes which give
them excellent daytime vision, except some
nocturnal geckos that have only rods.
Most lizards have external ears, snakes do not.
Gecko Feet, The Wall Climbers
Iguanas
Skinks
Chameleons
Glass Lizards
Lizards: Suborder Sauria
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Lizards are well adapted to living in hot, arid
climates like the desert.
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Lipids (fats) in their skin minimize water loss.
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Concentrated urine (uric acid) saves water.
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Some lizards, like the Gila monster of the
southwestern U.S., store fat in their tails, which
they use for an energy and water reservoir.
Ectotherms do not require as much energy to
live as do endotherms.
Gila Monster
Snakes: Suborder Serpentes
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Snakes are limbless and usually they lack pelvic
and pectoral girdles.
Numerous vertebrae and ribs which provide
support, protection, and more leverage for the
muscles to increase efficiency in locomotion.
The kinetic skull enables snakes to swallow prey
several times their size whole.
Snakes do not have movable eyelids, but they do
have permanently covered transparent eyelids.
Snake Skeleton
Snakes: Suborder Serpentes
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Snakes have no external ears.
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Most snakes have relatively poor vision.
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Some arboreal (tree-dwelling) snakes have
excellent binocular vision, that is useful for
tracking prey through branches.
Snakes do have internal ears that can detect
limited low frequency sounds.
Snakes are sensitive to ground vibrations.
Snakes: Suborder Serpentes
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Probably the most advanced sensory organs
used by the snakes to detect prey is the
detection of chemicals from a pair of pit-like
organs found in the roof of their mouth called
the Jacobson's organ.
Jacobson's organs are lined with olfactory
sensory neurons.
Their forked tongue, flicks the air and picks up
scent molecules, which are carried to the
Jacobson's organ.
Jacobson's Organ
Snakes: Suborder Serpentes
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Most snakes kill their prey by grabbing it and
swallowing it whole, but this is dangerous.
Constrictor snakes, kill their prey first by
constriction, then swallow the prey whole.
Some constrictors can swallow prey as large
as deer, leopards, and even crocodiles.
The muscles of constrictors are quite large,
and they slow them down.
So most constrictors tend to ambush their prey
rather than seek out their prey.
Constrictors
Snakes: Suborder Serpentes
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Other snakes kill their prey with venom before
swallowing it whole.
Vipers (Viperidae family) have large, movable
fangs at the front of their mouths.
Cobras, mambas, and coral snakes (Elapidae
family) have permanently erect fangs.
Some of the vipers are called pit vipers
because they possess special heat-sensitive pit
organs on their heads that detect infrared heat
produced by endotherms.
Vipers
Cobra and Coral Snake
Viper (Rattlesnake Teeth)
Cobra (Elapidae Teeth)
Pit Vipers
Snakes: Suborder Serpentes
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Many of the North American venomous snakes
are pit vipers, like the rattlesnakes, water
moccasins, and the copperheads.
Approximately 8,000 bites are reported in the
United States each year, but only 5-10 of those
8,000 reported result in death.
There are two types of snake venom; the
neurotoxic kind that attacks the optic nerves
causing blindness, and the phrenic nerve of the
diaphragm causing suffocation.
Snakes: Suborder Serpentes
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The other type of snake venom is a
hemorrhagin that destroys red blood cells,
blood vessels, and causes internal
hemorrhaging of internal tissues.
It is estimated that worldwide, 50,000-60,000
people die each year from snakebites.
Most are in third world tropical countries where
people are not properly fit with good shoes,
and medical facilities are lacking.
Order Sphenodonta: Tuataras
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Only two living species in New Zealand.
Strange lizard-like reptiles, although the skull is
different than that of snakes and lizards.
Skull is not movable like the kinetic skull of the
order Squamata (snakes and lizards).
They also have a median “third eye” with a
retina and lens and is sensitive to light, but it is
unusual because it is covered with scales.
Tuatara
Order Crocodilia: Crocodiles and Alligators
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Long, massive skull and jaw that is adapted to
provide a wide gape and a rapid, powerful bite.
Teeth are set in sockets, which is a feature
similar to some of the dinosaurs.
Crocodilians have a secondary palate, which is
similar to mammals and allows them to breath
when the mouth is full of water and/or food.
In crocodiles, some of the lower jaw teeth
overlap the upper jaw that is more narrow,
alligators lack this feature.
Crocodilian Palate Covering the Back
of the Throat
Crocodiles and Alligators
Crocodiles and Alligators
Order Crocodilia: Crocodiles and Alligators
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Crocodiles are known to attack large prey like
cattle, deer, and even people. Alligators are
less aggressive and seldom attack people.
Order Crocodilia: Crocodiles and Alligators
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Crocodilians lay their eggs in dead vegetation or in the
sand and guard the nest. When the eggs hatch, the
babies cry out to the mother and she digs them out.
After she digs them out she delicately places them in
her mouth and carries them safely to the water.
Soil temperatures determines the gender of the young
the same way as the turtles, except in crocodilians,
low soil temperatures produces females and high soil
temperatures produces males.
Crocodilian Parental Care