Transcript 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
Earth
• The reptiles thick skin helps prevent loss of body
water
• 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
hatch
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
Earth
• One determining factor that separates living
reptiles from amphibians is the type of eggs they
produce
• 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
years
• 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
Feeding
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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.
Respiration
• 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
prey
• 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.
Excretion
• 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
Response
• Most reptilian sense organs are well-developed
• Have complex eyes that contain photoreceptor
cells
• 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.
Movement
• The reptilian muscle and skeletal systems
exhibit many advances over those of
amphibians
• 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.
Reproduction
• 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
female
• From the outside, it is extremely difficult to
tell the sex of a reptile
• Most reptiles provide minimal care for their
young
Tuataras
• 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
animals.
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
temperature
• 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
Crocodilians
• 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
Turtles
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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
join
Turtles
• 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
predators
Turtles
• 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
attacked
How Reptiles Fit into the World
• Reptiles are important predators in many
ecosystems
• 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
Control
The Evolution of Temperature
Control
• 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
Control
• Turtles, snakes, and other modern reptiles are
ectotherms, which literally means heat from
outside
• These animals have low metabolic rates when
they are resting
• They do not generate much heat inside their
bodies
• Any heat they do generate is lost to their
surroundings
• These animals must pick up heat from the
environment
The Evolution of Temperature
Control
• 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
Control
• 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
disadvantages
The Evolution of Temperature
Control
• Ectotherms cannot remain active for long
periods
• 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
Birds
• About 8700 living species belonging to more
than 160 families
• There were even more kinds of birds in the
past
• 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
warm
• 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
water
– 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
dinosaur
• 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.
Feeding
• 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
diets
Feeding
• 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
Respiration
• 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
Respiration
• 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
exchange
• Birds are able to remove oxygen from air
when they inhale as well as when they
exhale
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
Excretion
• 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
Response
• Birds are quite intelligent
• Cerebrum controls behaviors such as flying,
nest building, care of young, courtship, and
mating
• Cerebellum and medulla are much like those of
reptiles
• Extraordinary well-developed eyes because of
large optic lobes in the brain
Response
• The senses of taste and smell are not well
developed
– 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.
Movement
• 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
Movement
• Bones are hollow so that the weight carried in
fight is less
• Large chest muscles that attach directly to the
sternum
• 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
Reproduction
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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
days
Reproduction
• 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
behaviors
• Some species mate for life
• Other pair up only briefly to mate
How Birds Fit into the World
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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
countries
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”