REPTILE NOTES

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REPTILE NOTES
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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.

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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.

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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.

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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.

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EXTENAL STRUCTURE AND MOVEMENT

• Chromatophores in reptiles are similar to those
  in amphibians.
• Cryptic coloration, mimicry, and aposematic
  coloration occur in reptiles.

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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.

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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.

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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.

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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 predators
  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.

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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.

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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.

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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.

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NUTRITION AND DIGESTIVE SYSTEM

• Vipers have hollow fangs.
• These fangs connect to venom glands that inject
  venom when the viper bites.

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NUTRITION AND DIGESTIVE SYSTEM

• The upper jaw bone of vipers is hinged so that
  when the snakes 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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Gas Exchange

• The ribs of turtles are a part of their shell, so
  movements of the body wall that have ribs
  attached is impossible.

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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.

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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.

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Temperature Regulation

• Most temperature regulations of reptiles are
  behavioral, especially in lizards.
• To warm itself, a lizard places itself at right
  angles to the suns 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 suns 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.

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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.

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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.

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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.

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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.

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NERVOUS AND SENSORY FUNCTIONS

• Reptiles have very complex sensory systems, as
  seen in a chameleons 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.

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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.

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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.

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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.

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NERVOUS AND SENSORY FUNCTIONS

• The structure of reptile ears varies.
• The ears of snakes detect underground vibrations.
  
• Snakes can also detect airborne vibrations.

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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.

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NERVOUS AND SENSORY FUNCTIONS

• The sense of smell is better developed in
  reptiles than amphibians.
• Many reptiles have Jacobsons organs, which are
  used to detect smells.
• The forked tongue of snakes and lizards are
  organs for tasting chemicals in the air.
• A snakes tongue goes out and then goes to the
  Jacobsons organ, which picks up odors.
• Tuataras use Jacobsons organs to taste objects
  held in the mouth.

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NERVOUS AND SENSORY FUNCTIONS

• Rattlesnakes and other pit vipers have
  heat-sensitive pit organs on each side of the
  face between the eye and nostril.
• These are used to detect objects with
  temperatures different from the snakes
  surroundings.

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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.

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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.

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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.

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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.

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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.

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REPRODUCTION AND DEVELOPMENT

• Parthenogenesis (fertilization with no male
  present) has been observed in six families of
  lizard and one species of snake.

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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.

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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.

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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.

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REPRODUCTION AND DEVELOPMENT

• After eggs are laid, reptiles usually abandon
  them.
• Most turtles bury their eggs in ground, under
  debris, or in burrows.

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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.

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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.

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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.

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