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Chapter 32 Reptiles and Birds


									Chapter 32: Reptiles and Birds

        Section 1: Reptiles
           What Is A Reptile?
• Reptiles are vertebrate animals that have
  lungs, a scaly skin, and a special type of egg –
  adaptations that enable them to live their
  entire life out of water
• Reptiles are widely distributed over much of the
• The reptiles thick skin helps prevent loss of body
• The tough, scaly layer of skin does not grow
  when the rest of the reptile grows, so it must be
  shed periodically when a reptile increases in size
          What Is A Reptile?
• Reptilian eggs are surrounded by a shell and
  several membranes that create a protected
  environment in which the embryo can develop
   – Amniotic egg
• Amniotic eggs also contain a yolk
• The yolk is rich in nutrients that the
  developing embryo uses until it is ready to
          What Is A Reptile?
• Reptiles have an efficient respiratory system
• To exchange gases with the environment,
  reptiles have at least one efficient lung
The chameleon, a modern reptile, moves slowly and
deliberately, creeping up to its insect prey. Its eyes
are able to move independently of each other, so that
one eye can guide its movements and the other can
sight the victim.
Unlike most amphibians, reptiles are able to survive
quite well in dry environments, as this snake in a
cactus shows. Their survival is due in part to their
dry, scaly skin, which must be shed periodically.
The reptile egg shows adaptations to
survive the dryness of life on land.
This tiny turtle has just hatched and is
breaking free of its shell.
          Evolution of Reptiles
• Because several fossils show characteristics of
  both amphibians and reptiles, it is difficult to say
  exactly when the first true reptiles appeared on
• One determining factor that separates living
  reptiles from amphibians is the type of eggs they
• Because we cannot tell what kind of eggs these
  fossil animals laid, they must remain on the
  amphibian-reptilian borderline
• These animals are often called transition fossils
         Evolution of Reptiles
• Throughout most of the Carboniferous Period,
  amphibians greatly outnumbered reptiles
• But during the Permian Period, the Earth’s surface
  and climate changed dramatically
• The climate became cooler and less humid
• Many of the great swamps dried up
• These changes made life difficult for a large
  number of water-dependent amphibians
• But such was not the case with the reptiles
• It was during this time that they began their great
  period of adaptive radiation
         Evolution of Reptiles
• One early reptile line developed into a fascinating
  group pf mammal like reptiles that displayed a
  mix of reptilian and mammalian characteristics
• Although these animals were extremely successful
  at first, they became extinct in just a few million
• Toward the end of the Triassic Period, about 195
  million years ago, the mammal like reptiles were
  suddenly replaced in the fossil record by another
  group of reptiles that had remained in the
  background for millions of years – the dinosaurs
          Evolution of Reptiles
• During the late Triassic and Jurassic Periods, a
  great adaptive radiation of the dinosaurs, or
  “terrible lizards,” took place
• The Triassic Period also saw the appearance of
  crocodiles and alligators, as well as the first birds
• At the end of the Cretaceous Period, about 65
  million years ago, something happened to cause a
  worldwide mass extinction
         Evolution of Reptiles
• Within a few million years, dinosaurs and most
  other animal and plant groups became extinct
• Whatever happened at the end of the Cretaceous
  Period resulted in the death of virtually all the
  great and terrible lizards
• The disappearance of the dinosaurs left open many
  niches for animals, both on land and in the sea
  Form and Function in Reptiles
• Reptiles exhibit numerous variations in
  structure and behavior
• Some – for example, turtle, crocodiles, and
  lizards – move about on four legs
• Others move about without legs
   – Snakes and certain lizards
•   Some are herbivores and others are carnivores
•   Some have sharp teeth to capture prey
•   Others kill their prey by drowning it first
•   Some reptiles have sticky tongues that can
    catch insects
All snakes are carnivores. Many snakes
eat small mammals. Because they are
able to stretch their jaws wide, snakes
swallow their prey whole. A chameleon
obtains its food by flicking out its
sticky tongue over a great distance.
Any insects within striking range are
gobbled up.
• May reptiles are able to expand their chest cavity to
  inhale and collapse the cavity to force air out
• Although most reptiles have two lungs, some
  species of snakes have only one
• You know that it is impossible for a person to
  breathe and swallow simultaneously
• Snakes have a special tube in the floor of their
  mouth through which they breathe, so they don’t
  suffocate in the time it takes them to swallow their
• This tube can be extended out of a snake’s mouth
  while it is dining
           Internal Transport
• Reptiles have a well-developed double-loop
  circulatory system
• One of the two loops brings blood to and from
  the lungs and the other loop brings blood to
  and from the rest of the body
• Have a well-developed heart
• Have a well-developed circulatory system
This illustration shows the internal organs of a
turtle. The turtle’s top shell is actually fused to its
vertebrae. Other reptiles differ slightly from this
body plan.
• Eliminate wastes in the form of urine, which is
  produced in the kidneys
• Urine flows through tubes directly into a
  cloaca similar to that of amphibians
• In some reptiles, a urinary bladder stores urine
  before it is expelled
• Most reptilian sense organs are well-developed
• Have complex eyes that contain photoreceptor
• Many snakes have a good sense of smell
• Some reptiles have simple ears to hear
  (eardrum, tympanic membrane)
• Some reptiles are able to gather heat
  information from their environment
Unlike certain snakes, the gila monster does not
have fangs to inject its venom. Instead, it bites its
prey and lets its venom flow into the open wound.
The fangs of this
rattlesnake are so long
they must fold in order
for the snake to close
its mouth. Note the
position of the animal’s
venom glands.
• The reptilian muscle and skeletal systems
  exhibit many advances over those of
• Reptiles with legs have larger, stronger limbs
  whose movements are well-controlled
• Snakes, which lost their legs in the course of
  evolution, move by pressing large ventral
  scales against the ground
                               Tiny flaps of skin on its toes
                               enable this gecko to cling to
                               surfaces as smooth as glass.

The sidewinder, a type of
rattlesnake, is able to move
along shifting desert sands
quite quickly.
• Reptiles lay eggs that hatch into animals that
  resemble small adults
• Virtually all reptiles reproduce through
  internal fertilization, which means that a
  male deposits sperm into the body of the
• From the outside, it is extremely difficult to
  tell the sex of a reptile
• Most reptiles provide minimal care for their
• The tuatara is the only surviving member of
  the order Rhynchocephalia
• Resembles reptiles that lived during the
  dinosaur age
• Tuataras are found only on a few small islands
  off the coast of New Zealand
• They are active at night
• They have a pineal gland that contains cells
  that are sensitive to light
• They use it to detect changes in day length
           Lizards and Snakes
• Order Squamata
• Most lizards have legs, clawed toes, external ears,
  and moveable eyelids
• Some have evolved into highly specialized forms
• The monitors are the only reptiles alive today that
  provide some idea of what small dinosaurs may
  have been like
   – Quite intelligent and active
   – Eat birds and mammals
   – Largest are the Komodo dragons
This male anole is displaying the bright
red patch below its chin. The Komodo
dragon is one of the largest lizards in
the world, reaching a length of about 3
meters. The frilled dragon gets its name
from a frill of skin around its neck that
can extend, thus making itself appear
larger and more fearsome to other
            Lizards and Snakes
• Snakes are lizards that have lost both pairs of legs
  during their evolution
• Although being legless may seem to be a
  disadvantage, snakes are efficient and effective
  predators in the niches they occupy
• The distribution of snakes on Earth is limited only by
• Snakes vary in size
• The ability of certain types of snakes to produce lethal
  poisons has caused people to fear snakes
   – More people in the US die from bee stings than
     snake bites
• Order Crocodilia
• Alligators, crocodiles, caimans, and gavials
• Crocodilians are among the largest living reptiles
   – Can grow up to 7m in length
• Live only in the tropics and subtropics, where the
  climate is warm year round
• Alligators and caimans live only in freshwater and
  are found in the Western Hemisphere
• Crocodiles may live in either fresh or salt water
  and are native to Africa, India, and Southeast Asia
• Order Chelonia
• Turtles live in water
• Tortoises live on land
• All have some sort of shell covering their body
• The shell consists of two parts: a dorsal part, or
  carapace, and a ventral part, or plastron
• The animal’s backbone is fused to the inside of
  the carapace, and its head, legs, and tail stick
  out through holes where carapace and plastron
• Tortoises usually have a high, domed carapace
  and stubby, elephant-like legs
• Tortoises pull into their shells to protect their
  more delicate body parts
• In some species,the front end of the plastron is
  hinged and folds up to further seal out
• Turtles are adapted to freshwater ponds and
  lakes or the open sea
• The legs and feet of many aquatic turtles have
  developed into flippers
• Certain aquatic species cannot pull back into
  their shell completely, but they do have
  powerful jaws that are capable of biting if
 How Reptiles Fit into the World
• Reptiles are important predators in many
• Sea turtles are now in danger of extinction
   – Turtle soup and turtle eggs
   – Used to manufacture jewelry
   – Destruction of nesting sites
Chapter 32: Reptiles and Birds

             Section 2:
    The Evolution of Temperature
  The Evolution of Temperature
• Control of body temperature is important
  for animals, particularly in habitats where
  temperature varies widely with time of day
  and with season
• Each animal species has its own preferred
  “operating range” of temperatures
• In terms of how they generate and control their
  body heat, animals can be classified into two
  basic groups: ectotherms and endotherms
  The Evolution of Temperature
• Turtles, snakes, and other modern reptiles are
  ectotherms, which literally means heat from
• These animals have low metabolic rates when
  they are resting
• They do not generate much heat inside their
• Any heat they do generate is lost to their
• These animals must pick up heat from the
  The Evolution of Temperature
• Birds and mammals are endotherms, which
  literally means heat from inside
• Birds and mammals have relatively high
  metabolic rates that generate a significant
  amount of heat, even when they are resting
• Body fat and either hair or feathers insulate the
  body, helping to retain that heat so that it is not
  lost to the environment
• Endotherms can move around at night more
  easily than ectotherms can
  The Evolution of Temperature
• In nature, lizards and snakes warm up when
  they need to by basking in the sun
• When their body reaches the right temperature,
  they go about their business
• If they get too hot during the day, reptiles duck
  into a cool burrow or under a rock to lose heat
• Neither endothermy nor ectothermy is superior
• Each strategy has its advantages and
  The Evolution of Temperature
• Ectotherms cannot remain active for long
• Endotherms remain active for a long time
• In climates that remain warm all the time,
  ectothermy is a way of conserving energy
• Endotherms burn lots of calories to generate
  body heat
Chapter 32: Reptiles and Birds

         Section 3: Birds
• About 8700 living species belonging to more
  than 160 families
• There were even more kinds of birds in the
• Paleontologists estimate that more than
  100,000 species of birds have become extinct
  since the Jurassic period
             What Is a Bird?
• Birds are endothermic reptile-like animals
  with an outer covering of feathers, two legs
  used for walking or perching, and front
  limbs modified into wings that usually do
  not have useful claws
• The single most important feature that
  distinguishes birds from reptiles is feathers
• Feathers help birds fly and also keep them
• Birds have several different kinds of feathers
               What Is a Bird?
• Contour feathers are large feathers that cover a bird’s
  body and wings
   – Used for flight
   – Contain barbs and barbules
   – Preening
• Down feathers grow underneath and between the
  contour feathers
   – Short, soft, and fluffy
   – Trap warm air close to a bird’s body
• Powder feathers are important to birds that live on or in
   – Repels water
Baby owls are covered with a
coat of down feathers. The air
spaces in these fluffy feathers
help insulate the birds from
temperature changes. Most of
the down feathers will later be
shed and a new coat of
contour feathers will grow in.
           Evolution of Birds
• The first fossil ever found of an early birdlike
  animal is called Archaeopteryx and dates from
  late in the Jurassic Period
• Its skeleton looks much like a small running
• Had teeth in its beak
• Had toes and claws on its wings
• There is much controversy over which fossils
  are those of birds and when birds first appeared
  on Earth
Archaeopteryx, which
lived about 147
million years ago, is
the oldest fossil that
has been confirmed to
be that of a bird.
    Form and Function in Birds
• Many characteristic features of birds differ
  dramatically among species adapted to
  different ways of life
   – Feathers, wings, bones, beaks, and legs
• It is important to study birds that live in
  different habitats and examine the adaptations
  they show
The huge talons of this soaring eagle help the
bird catch fish. Woodpeckers hear insects
chewing beneath the bark of a tree. The beak of
the woodpecker is strong enough to pierce the
bark, revealing the bug beneath it. The
featherless head of this vulture gives the bird a
sinister look, but a lack of head feathers serves a
useful function: A featherless head is easy to
keep clean. Because vultures often put their
head into the carcass of dead animals,
cleanliness is important.
• Birds have high metabolic rates and burn many
  calories just to keep warm
• For that reason, birds need to eat large amounts
  of food
• The digestive system of birds shows
  specializations for carnivorous and herbivorous
• Many birds have organs called crop and gizzard
• The crop is an enlarged area of the esophagus,
  where food can be stored and moistened before
  it enters the stomach
• The gizzard is a muscular part of the stomach
  that often contains small bits of gravel
  swallowed by a bird
   – Grinds the gravel and food together
       • Crushes food particles and makes them
         easier to digest
• Extremely efficient in taking in oxygen and
  eliminating carbon dioxide
• Bird lungs are connected at both the anterior
  and posterior to large air sacs in the body
  cavity and bones
• When a bird inhales, air travels through
  passageways that lead into the lungs
• Some stays in the lungs, however, most
  goes into the posterior air sacs
• When a bird exhales, air from the posterior
  air sacs passes into the lungs for gas
• Birds are able to remove oxygen from air
  when they inhale as well as when they
            Internal Transport
• Four-chambered heart and two separate
  circulatory loops
• One half of the heart receives oxygen-poor blood
  from the body and pumps this blood to the lungs
• Oxygen-rich blood returns to the other side of the
  heart to be pumped throughout the rest of the body
• This system ensures that oxygen collected by the
  lungs is distributed with maximum efficiency
• A bird’s heart beats quickly
   – From 150 to more than 1000 beats per minute
• Eliminate nitrogenous waste by filtering them
  from the blood in the kidneys
• Urine flows to the cloaca through the ureters
• Most water is reabsorbed in the cloaca, leaving
  uric acid crystals in a white paste like form
   – “bird droppings”
• Bird species that are surrounded by sea water
  have special salt glands near their eyes
   – Work like an extra pair of kidneys, except
     they specialize in secreting salt
• Birds are quite intelligent
• Cerebrum controls behaviors such as flying,
  nest building, care of young, courtship, and
• Cerebellum and medulla are much like those of
• Extraordinary well-developed eyes because of
  large optic lobes in the brain
• The senses of taste and smell are not well
   – Small olfactory lobes
• Lack external ears
• Some use a magnetic sense to navigate
   – Operates like a built-in compass, responding
     to Earth’s magnetic field
The huge forward-facing eyes of an owl help this
great bird hunt at night. Its eyes are able to spot a tiny
mouse foraging among the leaves on the dark floor of
a forest.
• Travel through different environments with
  wings, bodies, legs, and feet adapted for
  various types of locomotion
• Many variations in bird wings, depending on
  whether the animals soar like eagles, flap their
  wings steadily like robins, or hover in place
  like hummingbirds
• Bones are hollow so that the weight carried in
  fight is less
• Large chest muscles that attach directly to the
• Many birds use their flying ability to migrate
  between summer breeding grounds in the
  North and winter resting grounds in the South
  or the tropics
• A number of birds have lost their ability to fly
   – Ostriches and penguins
• Similar to that of reptiles
• Reproductive tracts open to the cloaca
• Male birds have no external reproductive organs
• Instead, mating birds press the lips of their
  cloacas close together to transfer sperm from
  male to female
• Most birds incubate their eggs until they hatch
• The time between laying and hatching varies
  among species from 13 days to more than 50
• When a chick is ready to hatch, it uses a small
  egg tooth on its bill to make a hole in the shell
• Some birds are able to take care of themselves
  as soon as they hatch
• Other newly hatched birds are blind and totally
  helpless when they hatch
• Birds have fascinating courtship and mating
• Some species mate for life
• Other pair up only briefly to mate
    How Birds Fit into the World
•   Serve as pollinators for a number of plants
•   Eat extraordinary numbers of insects
•   Down feathers are good insulators
•   Favorite foods around the world
•   Raising them is part of the economy in many
   How Birds Fit into the World
• Healthful source of protein
• Because domestic strains of chickens and
  turkeys do not fly, their chest muscles are
  seldom used, making this part of the bird the
  juicy and tender “white meat”
• The leg and thigh muscles of these birds, used
  constantly for walking and running, are the
  “dark meat”

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