Reptiles
1
Key features of Reptiles
1. Strong, bony skeletons and
toes with claws
2. Two pairs of limbs, except
snakes
3. Legs positioned vertically
for support of body and
movement on land 2
External Structural
Adaptations for Land
1. Claws-aid in climbing,
digging and movement in
various terrains
2. Toes modified into suctions
cups aid in climbing
3. Absence of limbs
Snakes use scaly skin and
highly developed skeletal
and muscular systems to
move
3
Ectothermic Metabolism
1. Regulate their temperature by
basking in the sun or seeking
shade
2. Become sluggish in very cold
temperatures
3. Intolerance to cold limits their
geographic range
4
Temperature Regulation
Regulate their temp by
behavior
Bask in sun to
speed up
metabolism
Hide in shade
to prevent
overheating
5
Reptiles Continued
1. Dry, scaly skin, almost watertight
2. Amniotic eggs, almost watertight
Contains a water and food supply
3. Respiration through well developed
lungs
Grape shaped chamber called alveoli
Alveoli increase the respiratory
surface area for gas exchange
Strong muscles in rib cage help to
move air in and out 6
Respiration
Well developed lungs
Tissues involved in
gas exchange are
located inside
body
Kept moist in even
in the driest
environments
7
Heart
1. Ventricle of heart partly divided by
a septum
2. Still incomplete separation of
oxygen-rich and oxygen-poor
blood
3. Crocodiles and alligators
have a ventricle that is totally
separated into two pumping
chambers 8
Circulation
Double loop circulation
9
Reproduction
1. Internal fertilization
2. Many reptiles are oviparous-young
hatch from eggs
3. Some lizards and snakes are
ovoviviparous-female retains eggs
in her body until shortly
before hatching or hatching
may occur inside her body 10
Excretion
Conserve water by excreting nitrogenous wastes in dry
or pasty form as crystals of uric acid
11
1st Orders of Reptiles
Squamata
Snakes and lizards
lower jaw is loosely connected
to skull allowing mouth to
open wide to accommodate
large prey
Lizards can regenerate tail,
but will not have vertebrae
Molting occurs in both 12
Squamata
1. Order consists of 5,640 species of lizards
and snakes
2. Loosely jointed upper jaw and paired
reproductive organs in males
3. Lizards-presence of limbs
4. Common lizards- iguanas, chameleons,
skinks and geckos
5. Live everywhere except Antarctic
6. Special adaptations- agility and
camouflage
7. 2 species are venomous- Gila monster
(SW U.S.) and beaded lizard (western
Mexico)
13
Squamata Continued
1. Blend with background
chameleons- remain
inconspicuous
2. Horned lizards- spiked
armor,when disturbed they
inflate,hiss and squirt blood
from eyes
3. Skinks and geckos- lose
their tails and regenerate-
escape from predators
4. Most lizards are small- .3m
in length; iguanas- 1m in
length
5. Largest lizards- monitors-
Komodo Dragon
(Indonesia) 3m (9.8 ft) in
length, 140 kg (308.6 lbs)
14
Adaptations of Snakes
15
Movement
1. A snake has a backbone of 100 to
400 vertebrae, with a pair of ribs
attached
2. Provides the framework for
thousands of muscles
3. Interaction of bones, muscles, and
skin enables a snake to move
various ways:
Example:
side winding
16
Feeding
Snakes eat animals, but lack
structural adaptations common to other carnivores
Snakes do not see or hear well, have no limbs, and
teeth and small mouth cannot rip and grind flesh
17
Locating Prey
1. Snakes evolved a sense of smell which they use
to locate their prey
2. Flicks its forked tongue to gather chemicals from
the environment
3. Transfers chemicals to two pits in the roof of the
mouth-Jacobsons organ where nerves are highly
sensitive to the chemicals
4. Some snakes inject toxic venom by biting with
fangs and injecting
5. Hemotoxins-attack the circulator system-disrupt
the clotting of blood.
6. Neurotoxins-disrupting the nerve pathways-
dangerous to respiratory and heart functions.
18
Reproduction
1. Most male snakes rely on
the scent of female snakes
of heir own species
2. Before mating, a male and
female snake may glide
alongside by side, with the
male stroking the female
with his chin and flicking his
tongue over her body
3. Fertilization is internal
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Reproduction Continued
1. Most snakes are oviparous
2. Female lays eggs that hatch
outside her body
3. To break out a hatchling uses a
special tooth which is lost soon
after
4. Other snakes are ovoviviparous
5. Female carries the eggs in her
body throughout development
6. Young are born live
7. All newborns must fend for
themselves, relying on their
many specialized adaptations
for survival on land
20
Defense
1. Natural selection resulted in modifications for defense.
2. Camouflage is beneficial for both seeking prey and hiding
from predators.
3. Many snakes are green and blend with foliage
4. Others are brown and hide against the bark of trees
21
Swallowing and Digesting Prey
1. A snakes upper and lower jaws
are hinged and move
independently.
2. when unhinged, the jaws
stretch to allow the mouth to
open extremely wide.
3. While swallowing it whole the
snake thrusts its windpipe into
the throat, allowing the snake
to breathe
4. The process of can take several
hours
22
Defense Continued
1. Some ward off danger
by rapidly changing
body shape
2. Extending a hood like
cobras
3. Some hiss
4. Others make
mechanical noises
5. Such as the rattle of the
rattlesnake.
23
2nd Order of Reptiles
Chelonia
Turtles and tortoises
Hard bony shell-dorsal
is carapace and
ventral is plastron
Lack teeth, but have beaks
Many herbivores but some are
carnivores 24
Chelonia
1. Order consists of about 265 species of
turtles and tortoises
2. Tortoise are terrestrial
3. Turtles live in water
4. Body covered by a shell made of hard
plates- 2 parts- a carapace and
plastron
5. Retractable head
6. Forelimbs of a marine turtle have
evolved into flippers and freshwater
turtles have webbed toes
7. Migratory behavior of sea and river
turtles
8. Returns to land to lay eggs
25
3rd Order of Reptiles
Crocodilia
Crocodiles and alligators
Most closely related
to dinosaurs
Aggressive carnivores
Care for their young after
hatching
26
Crocodilian
1. Order composed of 20 species of
large lizard-shaped reptiles-
crocodiles, alligators, caimans and
gavials
2. Crocodilians live in or near water in
tropical/ subtropical regions of the
world
3. Crocodiles-nocturnal animals;
Africa, Asia and Americas
4. Alligators-China and southern U.S.
5. Caimans-Central America, some in
Florida
27
1. Carnivorous
2. Eyes on head, nostrils
on top of snout
3. See and breathe while
in water
4. Parental care- both
parents care for young
by carrying in jaws
until development
28
4th Order of Reptiles
Rhynchocephalia
Tuataras
Two species native to
New Zealand
Most active at low
temperatures
29
Rhynochocephalia
1. Only living species-New
Zealand
2. Resembles a large lizard
about 60 cm long
3. Parietal eye-functions as a
thermostat-protects from
overheating
4. Active at low temperatures,
feed at night on insects,
worms and small animals
30
310 million
years ago… reptiles
were the
first vertebrates to
make the complete
transition to
life on land
An increase in competition Limited competition for the
for food and space among insects and plants that could
all the life-forms in aquatic
environments be used as food on the land
31
Adaptations to Land
32
Adaptations to Land
Amniotic Egg
Legs
Lungs
Scales or plates
33
Amniotic Egg
1. An egg with a protective
membrane and a porous shell
enclosing the developing
embryo
2. Egg forms a “nursery” to
protect the embryo
3. Egg derives its name from the
amnion, the thin membrane
enclosing the salty fluid in
which the embryo floats
4. Yolk sac encloses the yolk, a
protein rich food supply for
the developing embryo
5. Allantois stores the nitrogenous wastes produced by the
embryo until the egg hatches
34
1. The chorion regulates the exchange
of oxygen and carbon dioxide
between the egg and the outside
environment
2. Amniote egg is surrounded by a
leathery shell that may be hard in
some species (Birds) because of the
presence of calcium carbonate
3. The male places the sperm inside
the female before the shell is
formed. This is called internal
fertilization, makes water transport
of sperm unnecessary
35
Origin and Evolution
From the studies of fossils
and comparative
anatomy, biologists infer
that reptiles arose from a
group of ancestral
reptiles called
cotylosaurs, which lived
about 310 million years
ago.
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The End
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