Transcript Reptile Notes Parts 1 and 2

REPTILE NOTES
REPTILES
• The lifestyles of most reptiles have major
adaptations for living on land.
• For example, the chuckwalla, which is a lizard
common to the deserts of the southwestern
United States, can survive when temperatures get
over 104 degrees and during arid conditions when
there is little or no rain.
REPTILES
• To survive, chuckwallas disappear below ground
and aestivate (becoming dormant during the
summer).
• He will not come out until March, when rain falls.
• He will find water and drink, storing water in large
reservoirs under the skin.
• If threatened, a chuckwalla will hide in the nearest
rock crevice.
• It will inflate its lungs with air, making it “fatter”
and press up against the rock.
• Friction of its body scales make him nearly
impossible to dislodge.
EXTERNAL STRUCTURE
AND MOVEMENT
• The skin of reptiles has no respiratory function.
• Their skin is thick, dry, and contains keratin.
• Reptile skin also secretes pheromones that
function in sex recognition and defense.
EXTERNAL STRUCTURE
AND MOVEMENT
• All reptiles periodically shed the outer layer of skin
in a process called ecdysis.
• This process usually begins in the head region and
the skin usually comes off in one piece.
EXTENAL STRUCTURE AND
MOVEMENT
• Chromatophores in reptiles are similar to those in
amphibians.
• Cryptic coloration, mimicry, and aposematic
coloration occur in reptiles.
Support and Movement
• The reptile skeleton has a lot of bone to provide
greater support.
• The skull is longer than an amphibian skull.
• They also have a plate of bone, the secondary
palate, that partially separates the nasal passages
from the mouth cavity.
Support and Movement
• Reptiles have more cervical vertebrae than
amphibians do.
• The first two cervical vertebrae, the atlas and axis,
provide greater freedom of movement for the
head.
• The atlas allows nodding and the axis allows
rotation of the head.
Support and Movement
• The ribs of reptiles are also different.
• For instance, the ribs of snakes have muscular
connections to large belly scales to help with
movement.
• The cervical vertebrae of cobras have ribs that
may be flared to show aggression.
Support and Movement
• The tail vertebrae of many lizards have a vertical
fracture plate.
• When a lizard is grasped by the tail, these vertebrae
can be broken, and a portion of the tail is lost.
• Tail loss, or autotomy, is an adaptation that allows
a lizard to escape from a predator’s grasp, or the
disconnected piece of tail may distract a predator
from the lizard.
• The lizard will later regenerate the lost portion.
• Movement in reptiles is similar to salamanders.
NUTRITION AND DIGESTIVE
SYSTEM
• Most reptiles are carnivores, but turtles will eat
almost anything organic.
• The tongues of turtles and crocodiles do not come
out and are helpful for swallowing.
• Some lizards and the tuatara have sticky tongues
for capturing prey.
• The tongue extension of chameleons exceeds their
own body length.
NUTRITION AND DIGESTIVE
SYSTEM
• The most remarkable adaptation of snakes involve
the changes in their skull for feeding.
• The bones of the skull and jaws loosely join and can
spread apart to ingest prey much larger than a
normal head size.
• Each half of the upper and lower jaws can move
independently of each other.
NUTRITION AND DIGESTIVE
SYSTEM
• Teeth that point backward prevent prey escape
and help force the food into the esophagus.
• The glottis, or respiratory opening, is far forward in
the mouth so the snake can breathe while slowly
swallowing its prey.
NUTRITION AND DIGESTIVE
SYSTEM
• Vipers have hollow fangs.
• These fangs connect to venom glands that inject
venom when the viper bites.
NUTRITION AND DIGESTIVE
SYSTEM
• The upper jaw bone of vipers is hinged so that
when the snake’s mouth is closed, the fangs fold
back along the upper jaw.
• When the mouth opens, the upper jaw bone rotates
and causes the fangs to swing down.
• Because the fangs project outward from the
mouth, vipers may strike at objects of any size.
NUTRITION AND DIGESTIVE
SYSTEM
• Rear-fanged snakes have grooved rear teeth.
• Venom is sent along these grooves and into the prey
to quiet them during swallowing.
• These snakes usually do not strike, and most are
harmless to humans.
NUTRITION AND DIGESTIVE
SYSTEM
• Coral snakes, sea snakes, and cobras have fangs
that rigidly attach to the upper jaw.
• When the mouth is closed, the fangs fit into a
pocket in the outer gum of the lower jaw.
• Some cobras “spit” venom at their prey.
• If not washed from the eyes, the venom can cause
blindness.
NUTRITION AND DIGESTIVE
SYSTEM
• Venom glands are modified salivary glands.
• Most snake venoms are mixtures of neurotoxins
and hemotoxins.
• The venoms of coral snakes, cobras, and sea snakes
are primarily neurotoxins that attack nerve centers
and cause respiratory paralysis.
• The venoms of vipers are primarily hemotoxins that
break up blood vessels attack blood vessel linings.
CIRCULATION, GAS EXCHANGE,
TEMPERATURE REGULATION
• The circulatory system of reptiles is similar to
amphibians.
• Because reptiles are larger than amphibians, their
blood must travel under higher pressure to reach
distant body parts.
CIRCULATION, GAS
EXCHANGE, TEMPERATURE
REGULATION
• Like amphibians, reptiles have 2 heart atria that are
completely separated and a ventricle that is
incompletely divided.
• Blood low in oxygen enters the ventricle from the
right atrium, leaves the heart and goes to the
lungs.
• Blood high in oxygen enters the ventricle from the
lungs and leaves through a left and right artery.
CIRCULATION, GAS EXCHANGE,
TEMPERATURE REGULATION
• When turtles go into their shells, their method of
lung ventilation does not work.
• They also stop breathing during diving.
• During periods of apnea (no breathing), blood flow
to the lungs is limited, which conserves energy and
allows more efficient use of the oxygen supply.
Gas Exchange
• Reptiles exchange gases across internal surfaces to
avoid losing large amounts of water.
• They do have a larynx, but usually not vocal cords.
• Lungs are divided into spongy, connected
chambers.
• These chambers provide a large surface area for
gas exchange.
Gas Exchange
• The ribs of turtles are a part of their shell, so
movements of the body wall that have ribs
attached is impossible.
Temperature Regulation
• Unlike aquatic animals, terrestrial animals may face
temperature extremes that are not good for their
life.
• Temperature regulation is very important for
animals that spend their entire lives out of water.
• Most reptiles use external heat sources for
temperature regulation, and are ectothermic.
• Brooding Indian pythons, however, can use their
metabolism to increase temperature.
• Female pythons will coil around their eggs and
elevate their body temperature as much as 45
degrees above the air temperature.
Temperature Regulation
• Some reptiles can survive wide temperature
fluctuations (28-105 degrees).
• To sustain activity, body temperatures have to be
within a certain range (77-98.6).
• If that is not possible, the reptile will seek a retreat
where body temperatures can be in this range.
Temperature Regulation
• Most temperature regulations of reptiles are
behavioral, especially in lizards.
• To warm itself, a lizard places itself at right angles
to the sun’s rays, often on a warm surface, facing
the sun.
• It then presses its body to the surface to absorb
heat by conduction.
• To cool itself, a lizard places its body parallel to
the sun’s rays, seeks shade or burrows, or will
extend its legs and tail to reduce contact with
warm surfaces.
• In hot climates, many reptiles are nocturnal.
Temperature Regulation
• As temperatures rise, some reptiles begin panting,
which releases heat through evaporation.
• Marine iguanas divert blood to the skin while
basking in the sun and warm up quickly.
• When diving into cool waters, however, marine
iguanas reduce heart rate and blood flow to the
skin, which slows heat loss.
• Chromatophores also help temperature regulation.
Temperature Regulation
• In temperate regions, many reptiles handle cold
winter temperatures by entering torpor (decreased
activity in daily life).
• Reptiles that are usually solitary may migrate to a
common site called a hibernaculum, to spend the
winter.
• Heat loss from individuals in a hibernacula is
reduced because of clumping together.
Temperature Regulation
• Unlike true hibernators, a reptile body temperature
in torpor is not regulated, and if the winter is too
cold or the retreat too exposed, they will freeze
and die.
• Death from freezing is a major cause of mortality
for temperate reptiles.
NERVOUS AND SENSORY
FUNCTIONS
• The reptile brain is similar to that of other
vertebrates, although larger than the amphibian
brain.
• This increase in size is associated with improved
sense of smell.
• The optic lobes and cerebellum are also larger,
which indicates increase reliance on vision and
more coordinated muscle function.
NERVOUS AND SENSORY
FUNCTIONS
• Reptiles have very complex sensory systems, as seen
in a chameleon’s method of feeding.
• Its large eyes swivel independently, and each has a
different field of vision.
• Initially, the brain keeps both images separate, but
when prey is spotted, both eyes look at it.
• Their vision then determines if the prey is within
range of the tongue.
NERVOUS AND SENSORY
FUNCTIONS
• Vision is the dominant sense in most reptiles.
• Snakes focus on nearby objects by moving the lens
forward.
• Reptiles also have a greater number of cones than
amphibians do and probably have well-developed
color vision.
NERVOUS AND SENSORY
FUNCTIONS
• Upper and lower eyelids, a nictitating membrane,
and a blood sinus help protect and cleanse the
surface of the eye.
• The blood sinus, which is at the base of the
nictitating membrane, swells with blood to help
force debris to the corner of the eye, where it may
be rubbed out.
• Horned lizards squirt blood from their eyes by
rupturing this sinus to try and startle predators.
NERVOUS AND SENSORY
FUNCTIONS
• Some reptiles have a median eye that develops from
the roof of the forebrain.
• In the tuatara, it is an eye with a lens, a nerve, and
a retina.
• In other reptiles, the parietal eye is less developed.
• They are covered by skin and probably can not
form images.
• They can tell the difference between light and
dark periods and are used to help them orient to
the sun.
NERVOUS AND SENSORY
FUNCTIONS
• The structure of reptile ears varies.
• The ears of snakes detect underground vibrations.
• Snakes can also detect airborne vibrations.
NERVOUS AND SENSORY
FUNCTIONS
• In other reptiles, a tympanic membrane may be on
the surface or in a small depression on the head.
• The inner ear of reptiles is similar to amphibians.
NERVOUS AND SENSORY
FUNCTIONS
• The sense of smell is better developed in reptiles
than amphibians.
• Many reptiles have Jacobson’s organs, which are
used to detect smells.
• The forked tongue of snakes and lizards are organs
for tasting chemicals in the air.
• A snake’s tongue goes out and then goes to the
Jacobson’s organ, which picks up odors.
• Tuataras use Jacobson’s organs to taste objects
held in the mouth.
NERVOUS AND SENSORY
FUNCTIONS
• Rattlesnakes and other pit vipers have heatsensitive pit organs on each side of the face
between the eye and nostril.
• These are used to detect objects with
temperatures different from the snake’s
surroundings.
EXCRETION AND WATER
REGULATION
• The kidneys of reptiles are similar to fish and
amphibians.
• However, life on land, increased body size, and
higher metabolism require kidneys that can process
waste with little water loss.
• Most reptiles excrete uric acid.
• It is not toxic.
EXCRETION AND WATER
REGULATION
• Nocturnal habits and avoiding hot surface
temperatures during the day helps reduce water
loss.
• When water is available, many reptiles store large
quantities of water in lymphatic spaces under the
skin or in the urinary bladder.
• Many lizards have salt glands below the eyes for
helping the body get rid of excess salt.
REPRODUCTION AND
DEVELOPMENT
• The amniotic egg is not completely independent of
water.
• Pores in the eggshell allow gas exchange and also
water evaporation.
• These eggs require a huge amount of energy from
the parents.
• Some reptiles do provide parental care and they
may have to provide high humidity around the eggs.
• These eggs are often supplied with large quantities
of yolks for long development periods, and parental
energy can be invested in post-hatching care.
REPRODUCTION AND
DEVELOPMENT
• Fertilization must occur in the reproductive tract
of the female before protective egg membranes
can be laid down around the egg.
• All male reptiles, except tuataras, possess an
external organ for depositing sperm in the female.
• Lizards and snakes have hemipenes (a pair of
penises) at the base of the tail that are turned
inside out, like a glove.
REPRODUCTION AND
DEVELOPMENT
• Sperm may be stored in the female reproductive
tract.
• It may be stored for up to 4 years in some turtles,
and up to 6 years in some snakes.
• Sperm can be stored during the winter.
REPRODUCTION AND
DEVELOPMENT
• Parthenogenesis (fertilization with no male present)
has been observed in six families of lizard and one
species of snake.
REPRODUCTION AND
DEVELOPMENT
• Reptiles often have very complex reproductive
behaviors that may involve males actively seeking
out females.
• Head-bobbing displays by some male lizards reveal
bright patches of color on the throat and folds of
skin.
REPRODUCTION AND
DEVELOPMENT
• Courtship in snakes is based mainly on touch.
• Tail-waving displays are followed by the male
running his chin along the female, entwining his
body around hers.
REPRODUCTION AND
DEVELOPMENT
• Lizards and snakes also use sex pheromones to
assess the reproductive condition of a potential
mate.
• Vocal sounds are only important to crocodiles.
• During breeding season, males are hostile and may
bark or cough as a warning to other males.
• Roaring is used to attract females, and mating
occurs in water.
REPRODUCTION AND
DEVELOPMENT
• After eggs are laid, reptiles usually abandon them.
• Most turtles bury their eggs in ground, under
debris, or in burrows.
REPRODUCTION AND
DEVELOPMENT
• About 100 species of reptile provide care for their
eggs.
• One example is the American alligator.
• The female builds a nest of mud and grass.
• She hollows out the center, partially fills it with
mud, lays her eggs, and then covers them.
REPRODUCTION AND
DEVELOPMENT
• Temperatures within the nest within the nest
influences the sex of the hatchlings.
• Temperatures at or below 88.7 will result in female
offspring.
• Temperatures between 90.5 and 91.4 will result in
male offspring.
• Temperatures around 89.6 results in male and
female offspring.
REPRODUCTION AND
DEVELOPMENT
• The female remains near the nest throughout
development to protect the eggs from predators.
• She helps hatchlings from the nest in response to
high-pitch calls and carries them in her mouth to
water.
• She may remain with them for up to 2 years.
• Young eat scraps she drops when she feeds and will
eat some small vertebrates they can catch on their
own.