Transcript What Is a Bird?

Biology
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What Is a Bird?
What characteristics do birds have in
common?
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What Is a Bird?
What Is a Bird?
Birds are reptilelike animals that maintain
a constant internal body temperature.
Birds have an outer covering of feathers;
two legs that are covered with scales and
are used for walking or perching; and
front limbs modified into wings.
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What Is a Bird?
Feathers separate birds from all other living animals.
Feathers are made mostly of protein and develop
from pits in the birds' skin.
Feathers help birds fly and also keep them warm.
The two main types of feathers are contour and
down.
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What Is a Bird?
Feathers
Barb
Contour feather: Contour
feathers provide the lifting force
and balance needed for flight.
Down feather: Down
feathers trap air close to the
body and keep the bird warm.
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Barbule: The hooks on
each barbule fit together,
holding them flat.
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Evolution of Birds
Evolution of Birds
Paleontologists agree that birds evolved from
extinct reptiles.
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Embryos of birds and reptiles develop within
amniotic eggs.
•
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Both excrete nitrogenous wastes as uric acid.
Bones that support the limbs, and other
skeleton parts, are similar in both groups.
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Evolution of Birds
Archaeopteryx was the first birdlike fossil discovered.
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Archaeopteryx looked like a dinosaur, but it had
feathers.
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It had teeth in its beak, a bony tail, and toes and
claws on its wings.
•
It may be a transitional species between
dinosaurs and birds.
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Evolution of Birds
Other fossil evidence leads some to hypothesize that
birds and dinosaurs both evolved from an earlier
common ancestor.
The origin of birds is still not completely resolved.
New fossils of ancient birds are being found all the
time.
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Evolution of Birds
Evolution of Birds
Dinosaurs
Modern reptiles
Modern birds
Saurischia
(lizard-hipped
dinosaurs)
Ornithischia
(bird-hipped
dinosaurs)
Archaeopteryx
Ancestor of
dinosaurs
Reptile ancestor
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Form, Function, and Flight
How are birds adapted for flight?
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Form, Function, and Flight
Form, Function, and Flight
Birds have a number of adaptations that
enable them to fly, including:
• highly efficient digestive, respiratory, and
circulatory systems
• aerodynamic feathers and wings
• strong, lightweight bones
• strong chest muscles
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Form, Function, and Flight
Body Temperature Control
Birds generate their own body heat and are called
endotherms.
Endotherms have a high rate of metabolism.
Metabolism produces heat.
Feathers insulate a bird enough to conserve most
of its metabolic energy, allowing it to keep warm.
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Form, Function, and Flight
Feeding
Birds need to eat a lot of food to produce the heat
energy they need to maintain metabolism.
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Form, Function, and Flight
Birds’ beaks, or bills, are adapted to the type of food
they eat.
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Insect-eating birds have short, fine bills that pick
ants and insects off leaves and branches, or can
catch flying insects.
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Seed-eaters have short, thick bills.
Carnivorous birds shred their prey with strong
hooked bills.
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Form, Function, and Flight
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Long, thin bills gather nectar or probe mud for
worms and shellfish.
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Large, long bills pick fruit from branches.
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Long, flat bills grasp fish.
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Form, Function, and Flight
Birds do not have teeth and cannot chew.
Many birds have specialized structures to help digest
food.
The crop is a structure at the lower end of the
esophagus in which food is stored and moistened.
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Form, Function, and Flight
Esophagus
Crop
When a bird eats,
food moves down
the esophagus and
is stored in the crop.
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Form, Function, and Flight
In some birds the crop has a second function.
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During nesting season, the crop produces a
substance rich in protein and fat.
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Parents regurgitate this to feed their newly
hatched young.
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This provides young birds with materials they
need to grow.
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Form, Function, and Flight
First chamber of stomach
Gizzard
Moistened food passes
to the stomach, a twopart chamber.
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First chamber of stomach
Gizzard
The first chamber
secretes acid and
enzymes.
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First chamber of stomach
Gizzard
The partially digested
food moves to the
second chamber, the
gizzard.
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Form, Function, and Flight
Birds that eat meat or fish have an expandable area
in which large amounts of soft food can be stored.
Birds that eat insects or seeds have a muscular
organ called the gizzard that helps in the mechanical
breakdown of food.
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The muscular walls of the
gizzard squeeze the contents,
while small stones grind the
food.
Gizzard
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Form, Function, and Flight
Small intestine
Large intestine
As digestion
continues, the food
moves through the
intestines.
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Form, Function, and Flight
Cloaca
Undigested food is
expelled through
the cloaca
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Form, Function, and Flight
Respiration
Birds have a highly-efficient way of taking in
oxygen and eliminating carbon dioxide.
Air enters air sacs.
It flows through the lungs where gas exchange
takes place.
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Air flows in a single direction.
The one-way flow of air:
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constantly exposes the lungs to oxygen-rich air.
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maintains a high metabolic rate.
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provides efficient extraction of oxygen, which
enables birds to fly at high altitudes where the
air is thin.
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Circulation
Birds have four-chambered hearts and two
circulatory loops.
There is complete separation of oxygen-rich and
oxygen-poor blood.
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Oxygen-poor blood from the body is pumped to the
lungs.
Oxygen-rich blood returns from the lungs and is
pumped to the rest of the body.
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Bird Heart
Domestic pigeon
Heart
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Excretion
Excretion in birds is similar to that of most living
reptiles.
Nitrogenous wastes are removed from the blood
by the kidneys, converted to uric acid, and
deposited in the cloaca.
Most of the water is reabsorbed, leaving uric acid
crystals in a white, pasty form.
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Response
Birds have well-developed sense organs, which
are adaptations that enable them to coordinate the
movements required for flight.
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Bird Brain
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Birds’ brains can quickly interpret and respond to
signals.
• The cerebrum controls behavior and is large.
• The cerebellum coordinates the movement of the
wings and legs; it is larger in birds than in reptiles.
• The medulla oblongata coordinates basic body
processes.
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Birds have well-developed eyes which allow them to
see color very well.
Most bird species can hear quite well.
Taste and smell are not well developed in most birds.
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Movement
Some birds, such as ostriches and penguins
cannot fly.
Most birds, however, can fly.
The skeletal and muscular systems of flying birds
exhibit adaptations that enable flight.
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Skeletal System
of a Bird
Vertebra
Skull
Collarbone
(wishbone)
Pelvic girdle
Strut
Tailbone
Pectoral griddle
Air
space
Sternum
Rib cage
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Form, Function, and Flight
In flying birds, many large bones are fused together,
making the skeleton rigid.
These form a frame that anchors the muscles used
for flight.
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Bones are
strengthened by struts.
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Air spaces make bones
lightweight.
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Birds have large chest muscles that power the
upward and downward wing strokes necessary for
flight.
Muscles attach to a keel that runs down the front of
an enlarged breastbone, or sternum.
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Reproduction
Both male and female reproductive tracts open into
the cloaca.
Mating birds press their cloacas together to
transfer sperm from male to female.
Some male birds have a penis that transfers sperm
to the female.
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Form, Function, and Flight
Bird lay amniotic eggs that have hard outer shells.
Most birds incubate their eggs until the eggs hatch.
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When a chick is ready to hatch, it makes a hole in the
shell with a small tooth on its bill.
Once the bird has hatched, it rests for a while and
lets its feathers dry.
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Groups of Birds
Groups of Birds
There are nearly 30 different orders of birds.
The largest order of birds is the passerines, or
perching birds.
Other groups of birds include: pelicans, parrots,
birds of prey, cavity-nesting birds, herons, and
ostriches.
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Ecology of Birds
Ecology of Birds
Birds interact with ecosystems and humans in
many ways.
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Hummingbirds pollinate flowers.
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Insect-eating birds catch insects, controlling
populations.
Fruit-eating birds disperse seeds in their
droppings.
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Ecology of Birds
Many birds migrate long distances, usually
seasonally.
Some species use stars and other celestial bodies as
guides.
Others use a combination of landmarks and cues
from Earth’s magnetic field.
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Continue to:
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A bird with a short, thick bill probably eats
a. fish.
b. seeds.
c. insects.
d. fleshy fruit.
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Archaeopteryx has characteristics of both
a. modern birds and ancient birds.
b. amphibians and reptiles.
c. reptiles and modern birds.
d. amphibians and modern birds.
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Which of the following bird adaptations is NOT
associated with flight?
a. bones with many hollow air spaces
b. air sacs in addition to lungs
c. gizzard
d. contour feathers
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The largest order of birds is the
a. perching birds.
b. birds of prey.
c. pelicans and relatives.
d. penguins.
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Which of the following birds assists in pollinating
flowering plants?
a. pelican
b. hummingbird
c. raptor
d. heron
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