Transcript Reptile Notes Part 1

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.