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Chapter Presentation
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Standardized Test Prep
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Chapter 42
Birds
Table of Contents
Section 1 Origin and Evolution of Birds
Section 2 Characteristics of Birds
Section 3 Classification
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Chapter 42
Section 1 Origin and Evolution of
Birds
Objectives
• Identify and describe seven major characteristics of
birds.
• List three similarities between birds and dinosaurs.
• Describe the characteristics of Archaeopteryx.
• Summarize the two main hypotheses for the
evolution of flight.
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Chapter 42
Section 1 Origin and Evolution of
Birds
Characteristics
There are seven characteristics all birds share
•
•
•
•
•
•
•
Feathers
Wings
Lightweight, rigid skeleton
Endothermic metabolism
Unique respiratory system
Beak
Oviparity
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Chapter 42
Section 1 Origin and Evolution of
Birds
Characteristics of Birds
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Chapter 42
Section 1 Origin and Evolution of
Birds
Evolution
There are several similarities between birds and
some dinosaurs:
• Flexible S-shaped neck
• Unique ankle joint
• Hollow bones
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Chapter 42
Section 1 Origin and Evolution of
Birds
Evolution, continued
The oldest known bird fossils are in the genus
Archaeopteryx, which date from the late Jurassic
Characteristics of Archaeopteryx
• Feathers on forelimbs, body and tail
• Hollow bones and a furcula (fused collarbones
also called a wishbone)
• Teeth
• Claws on forelimbs
• Long, bony tail
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Chapter 42
Section 1 Origin and Evolution of
Birds
Evolution, continued
Archaeopteryx had characteristics of birds and dinosaurs.
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Chapter 42
Section 1 Origin and Evolution of
Birds
Evolution, continued
Origin of Flight
• One hypothesis proposes that the ancestors of
birds were tree dwellers that developed the ability
to glide between trees.
• Another hypothesis suggests that the ancestors
of birds were ground-dwelling and first used
feathers to stabilize them when they leapt after
prey.
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Chapter 42
Section 1 Origin and Evolution of
Birds
Phylogenetic Diagram of Birds, Reptiles, and
Mammals
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Chapter 42
Section 1 Origin and Evolution of
Birds
Adaptations for Flight
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Chapter 42
Section 2 Characteristics of
Birds
Objectives
• Describe the structure of a contour feather.
• Identify two modifications for flight seen in a bird’s
skeletal system.
• Contrast the function of the gizzard with that of the crop.
• Trace the movement of air through the respiratory system
of a bird.
• Explain the differences between altricial and precocial
young.
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Chapter 42
Section 2 Characteristics of
Birds
Characteristics of Birds
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Chapter 42
Section 2 Characteristics of
Birds
Feathers
Feathers are modified scales that serve two primary functions:
providing lift for flight and conserving body heat.
• Feathers develop from tiny pits in the skin called follicles.
• Feathers have a shaft, two vanes, barbs and barbules.
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Chapter 42
Section 2 Characteristics of
Birds
Feathers, continued
There are three basic types of feathers:
• Down feathers - soft, fluffy feathers that cover
young birds and provide an insulating undercoat in
adults
• Contour feathers - smooth feathers that give adult
birds’ bodies a streamlined shape and provide
insulation
• Flight feathers - specialized contour feathers
located on the wings and tail that are long and rigid
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Chapter 42
Section 2 Characteristics of
Birds
Feathers, continued
Feathers are cared for by a process called preening.
• Preening occurs when birds use their beaks to rub
their feathers with oil.
• The preen gland is located at the base of the tail
and secretes oils that keep feathers healthy and
waterproof.
• Birds periodically shed and regrow their feathers in
a process called molting.
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Chapter 42
Section 2 Characteristics of
Birds
Contour Feather Structure
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Chapter 42
Section 2 Characteristics of
Birds
Parts of a Feather
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Chapter 42
Section 2 Characteristics of
Birds
Preening
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Chapter 42
Section 2 Characteristics of
Birds
External Structure of Birds—Bald Eagle
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Chapter 42
Section 2 Characteristics of
Birds
Skeleton and Muscles
• The avian skeleton is light and strong.
• Bones are thin and hollow.
• Many bones are fused, which makes the skeleton
more rigid than that of a reptile or mammal.
• A large keel-shaped sternum allows attachment
of large flight muscles.
• The pygostyle, fused terminal vertebrae, supports
the tail feathers.
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Chapter 42
Section 2 Characteristics of
Birds
Avian Skeleton
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Chapter 42
Section 2 Characteristics of
Birds
Skeleton and Muscles, continued
• Flight involves complex wing movements. Each
movement uses a different set of muscles.
• Birds have large, powerful flight muscles in the
breast and wings.
• In some birds, flight muscles account for up to
50% of the body weight.
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Chapter 42
Section 2 Characteristics of
Birds
Metabolism
• Birds are endothermic.
• Birds have a very high metabolic rate.
• Rapid breathing and digestion of large quantities
of food support this high metabolic rate.
• Birds’ digestive and respiratory systems have
evolved to support a high metabolism.
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Chapter 42
Section 2 Characteristics of
Birds
Digestive and Excretory Systems
The avian digestive system consists of:
•
•
•
•
Beak - breaks open or tears apart food
Esophagus - passage from the mouth to the crop
Crop - stores and moistens food
Stomach - consists of two parts
– proventriculus - acids and digestive enzymes begin
breaking down food
– gizzard - kneads and crushes food aided by stones
which the bird swallows
• Small intestine - absorbs nutrients
• Large intestine - absorbs water
• Cloaca - eliminates wastes from the body
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Chapter 42
Section 2 Characteristics of
Birds
Bird Digestive System
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Chapter 42
Section 2 Characteristics of
Birds
Digestive and Excretory Systems, continued
The avian excretory system is efficient and
lightweight.
• Birds have two kidneys that filter nitrogenous
wastes.
• Birds do not have a urinary bladder.
• Birds excrete concentrated uric acid, which
conserves water.
• Uric acid mixes with feces and is excreted
through the cloaca.
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Chapter 42
Section 2 Characteristics of
Birds
Respiratory System
• The avian respiratory system is highly efficient
and allows birds to maintain a high metabolic
rate.
• Air sacs connected to the lungs provide a
constant flow of oxygenated air to the lungs.
• This also allows birds to function at high
altitudes.
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Chapter 42
Section 2 Characteristics of
Birds
Avian Lung Structure
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Chapter 42
Section 2 Characteristics of
Birds
Bird Lungs
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Chapter 42
Section 2 Characteristics of
Birds
Circulatory System
The avian circulatory system is similar to that of
both crocodiles and mammals.
• Birds have a four chambered heart.
• Deoxygenated blood is completely separated
from oxygenated blood in the heart.
• Birds have a relatively rapid heartbeat.
• Unlike mammals, avian red blood cells have
nuclei.
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Chapter 42
Section 2 Characteristics of
Birds
Avian Heart Structure
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Chapter 42
Section 2 Characteristics of
Birds
Bird Heart
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Chapter 42
Section 2 Characteristics of
Birds
Nervous System and Sense Organs
• Birds have large brains relative to their body size.
• The cerebellum, which controls flight related
functions, is large.
• The cerebrum, which controls complex behavior,
is also well developed.
• The optic lobes are also very large.
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Chapter 42
Section 2 Characteristics of
Birds
Parts of a Bird Brain
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Chapter 42
Section 2 Characteristics of
Birds
Nervous System and Sense Organs, continued
Birds have very good vision.
• Vision is important for flight and feeding.
• Most birds have strong color vision.
• Some birds have eyes located near the sides of
the head, which provide a wide field of vision.
• Predatory birds have eyes that are more forwardfacing, which provides depth perception.
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Chapter 42
Section 2 Characteristics of
Birds
Nervous System and Sense Organs, continued
Birds have good hearing.
• Hearing is important for songbirds and nocturnal
birds.
• Nocturnal predators rely on hearing to locate prey.
• Birds lack external ears.
• Owls have feathers around their ear openings that
direct sound into the ear.
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Chapter 42
Section 2 Characteristics of
Birds
Reproduction
Male:
• Sperm is produced in two testes, located anterior
to the kidneys.
• Sperm passes through small tubes called vasa
deferentia (singular vas deferens).
• Sperm exits through the cloaca.
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Chapter 42
Section 2 Characteristics of
Birds
Reproduction, continued
Female:
• Eggs are produced in a single ovary, located on
the left side of the body.
• Eggs are released by the ovary and pass into a
funnel shaped tube called the oviduct.
• Eggs are fertilized in the oviduct.
• In the oviduct, eggs are encased in a protective
covering and a shell.
• Eggs are released through the cloaca.
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Chapter 42
Section 2 Characteristics of
Birds
Reproduction, continued
Nest building and parental care
• Birds usually lay their eggs in a nest.
• One or both parents warm (incubate) the eggs
and guard the nest.
• Birds sit on their eggs and cover them with a
thickened featherless patch of skin called the
brood patch.
• Birds usually provide extensive parental care.
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Chapter 42
Section 2 Characteristics of
Birds
Reproduction, continued
Birds have two general patterns for rearing young
• Precocial: Young incubate for long periods.
Young can walk, swim, and feed as soon as they
hatch. This pattern is most often seen in groundnesting birds.
• Altricial: Eggs hatch quickly. Young hatch blind,
featherless, and helpless and require extensive
parental care. This pattern is most often seen in
birds that nest above ground.
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Chapter 42
Section 2 Characteristics of
Birds
Internal Structure of Birds—
Bald Eagle
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Chapter 42
Section 2 Characteristics of
Birds
Anatomy of a Bird
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Chapter 42
Section 2 Characteristics of
Birds
Migration
Migration is the seasonal movement of animals from one habitat to
another habitat.
• Many birds nest in temperate regions, and spend winters in
tropical regions.
• Bird migration patterns are studied by ornithologists biologists who study birds.
• Birds may use landmarks, star position, sun position,
Earth’s magnetic field, changes in air pressure, or lowfrequency sounds to navigate during migration.
• Many species rely on fat reserves for energy during
migration. Some species gather and feed along the
migration route at places called staging sites.
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Chapter 42
Section 3 Classification
Objectives
• Describe the relationship between beak shape and
diet in birds.
• List 10 major orders of living birds, and name an
example of each order.
• Describe the function of the syrinx.
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Chapter 42
Section 3 Classification
Diversity
Beak and foot adaptation reveal information about a
bird’s habitat and diet, for example:
• Predators: powerful, hooked beaks and sharp
talons (claws)
• Seed eaters: strong wide beaks, small feet for
perching
• Nectar feeders: long thin beaks
• Flightless birds: strong legs for walking and
running
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Chapter 42
Section 3 Classification
Avian Adaptations
Type of Bird
Songbirds (e.g., cardinal, robin)
Beak Adaptations
Seed-cracking:
Short, thick,
strong beak
Foot Adaptations
Perching: Toes can cling to
branches; one toe points backwards
Type of Bird
Beak Adaptations
Foot Adaptations
Long-legged waders
Fishing: Long, slender, spearshaped beak for fishing
Wading: Long
legs; toes spread
out over a large
area to support
bird on soft
surfaces
Wood peckers
Drilling: Strong, chisel-like beak
Grasping: Feet with two toes
pointing forward and two pointing
backward
Parrots
Cracking, tearing: Short, stout,
hooked beak used to crack seeds
and nuts and to tear vegetation
Climbing/grasping: Strong toes, two
pointing forward, two pointing
backward; adapted for perching,
climbing, and holding food.
Insect-catching:
Long, slender
beak for probing
Hummingbirds
Probing: Thin, slightly curved beak
for inserting into flowers to sip nectar
Hovering: Legs so small the bird
cannot walk on the ground; tiny feet
Birds of prey
Tearing: Curved, pointed beak for
tearing apart prey
Grasping: Powerful, curved talons
for seizing and gripping prey
Ducks
Sieving: Long, flattened, rounded bill
Swimming: Three toes linked by
webs for improved swimming
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Chapter 42
Section 3 Classification
Beak Adaptations and Bird Diversity
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Chapter 42
Section 3 Classification
Foot Adaptations and Bird Diversity
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Chapter 42
Section 3 Classification
Diversity, continued
• Taxonomists divide birds into about 23 orders.
• Morphology (body form), protein sequences, DNA
sequence, and other evidence are used to classify birds.
• Ten of the most familiar orders are listed below.
»
»
»
»
»
»
»
»
»
»
Anseriformes
Strigiformes
Apodiformes
Poittaciformes
Piciformes
Passeriformes
Columbiformes
Ciconiiformes
Galliformes
Struthioniformes
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Chapter 42
Section 3 Classification
Diversity, continued
Order Anseriformes
• Includes swans, geese, ducks and other
waterfowl
– Webbed feet
– Flattened bill
– Precocial young
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Chapter 42
Section 3 Classification
Diversity, continued
Order Strigiformes
• Includes owls
– Nocturnal
– Keen vision with forward facing eyes
– Predators
– Keen hearing
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Chapter 42
Section 3 Classification
Diversity, continued
Order Apodiformes
• Includes hummingbirds and swifts
– Small birds with tiny feet
– Fast flying, some can hover
– Insectivores and nectar feeders
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Chapter 42
Section 3 Classification
Diversity, continued
Order Psittaciformes
• Includes parrots, parakeets, macaws, cockatoos, cockatiels
and their relatives
– Seed and fruit eaters
– Strong hooked beaks for opening seeds
– Two forward facing and two backward facing toes, for
climbing and perching
– Vocal birds, some can mimic human speech
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Chapter 42
Section 3 Classification
Diversity, continued
Order Piciformes
• Includes tree dwelling birds such as
woodpeckers, honeyguides and toucans.
– All nest in tree cavities
– Two forward and two backward facing toes
– Woodpeckers have sharp, chisel-like bills
– Toucans are fruit eaters and have large bills
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Chapter 42
Section 3 Classification
Diversity, continued
Order Passeriformes
• Includes robins, warblers, blue jays, wrens, and
other common North American birds
– Perching birds with three toes forward and one
backward, with enlarged rear toe for grip
– Seed, fruit, insect, and nectar feeders
– Many are songbirds. Males use elaborate
songs to attract females. The song is
produced in a structure called the syrinx.
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Chapter 42
Section 3 Classification
Diversity, continued
Order Columbiformes
• Includes pigeons and doves
– Large breasts and small heads
– Fruit or grain eaters with small beaks and
short legs
– Both sexes feed young with nutritious fluid
produced in the crop, called crop milk
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Chapter 42
Section 3 Classification
Diversity, continued
Order Ciconiiformes
• Includes herons, storks, ibises, egrets, raptors,
vultures and penguins
– Highly diverse group
– Many are wading birds that eat fish and frogs,
with long legs, long neck, and long bill
– All are carnivorous
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Chapter 42
Section 3 Classification
Diversity, continued
Order Galliformes
• Includes turkeys, chickens, pheasants, grouse,
and quails
– Commonly called fowl
– Usually plump bodies, may be poor fliers
– Grain and insect eaters
– Precocial young
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Chapter 42
Section 3 Classification
Diversity, continued
Order Struthioniformes
• Includes ostriches, emus, rheas, and cassowaries
– Includes the worlds largest birds
– Fightless birds with small wings and long
powerful legs for running
– Ostriches can reach speeds of 55 mph
– Ostriches have two toes per foot
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Chapter 42
Section 3 Classification
Types of Birds
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Chapter 42
Standardized Test Prep
Multiple Choice
1. Which of the following characteristics of
Archaeopteryx is not shared by modern birds?
A. tail
B. teeth
C. furcula
D. feathers
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Chapter 42
Standardized Test Prep
Multiple Choice
1. Which of the following characteristics of
Archaeopteryx is not shared by modern birds?
A. tail
B. teeth
C. furcula
D. feathers
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
2. Which of the following characteristics do birds share
with dinosaurs?
F. crop
G. lack of teeth
H. presence of feathers
J. structure of the ankle joint
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
2. Which of the following characteristics do birds share
with dinosaurs?
F. crop
G. lack of teeth
H. presence of feathers
J. structure of the ankle joint
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Chapter 42
Standardized Test Prep
Multiple Choice
3. What is the function of the preen gland?
A. to produce digestive enzymes
B. to control salt balance in the body
C. to release scents that help attract mates
D. to produce an oily substance used to condition the
feathers
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Chapter 42
Standardized Test Prep
Multiple Choice
3. What is the function of the preen gland?
A. to produce digestive enzymes
B. to control salt balance in the body
C. to release scents that help attract mates
D. to produce an oily substance used to condition the
feathers
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
4. Which bone supports the tail feathers?
F. ulna
G. furcula
H. pygostyle
J. pelvic girdle
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
4. Which bone supports the tail feathers?
F. ulna
G. furcula
H. pygostyle
J. pelvic girdle
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Chapter 42
Standardized Test Prep
Multiple Choice
The graph below shows the effect of varying clutch size on
the number of surviving offspring in one bird species.
Use the graph to answer the question that follows.
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Chapter 42
Standardized Test Prep
Multiple Choice
5. Based on these data, which of the following
statements is true for this species?
A. The optimal number of eggs in a clutch is seven.
B. The greater the clutch size is, the greater the
number of surviving offspring.
C. Nests with five eggs produced the fewest number
of surviving offspring.
D. More offspring died in nests containing eight eggs
than in nests containing nine eggs.
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Chapter 42
Standardized Test Prep
Multiple Choice
5. Based on these data, which of the following
statements is true for this species?
A. The optimal number of eggs in a clutch is seven.
B. The greater the clutch size is, the greater the
number of surviving offspring.
C. Nests with five eggs produced the fewest number
of surviving offspring.
D. More offspring died in nests containing eight eggs
than in nests containing nine eggs.
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
6. crop milk : crop :: song :
F. syrinx
G. trachea
H. proventriculus
J. anterior air sacs
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Chapter 42
Standardized Test Prep
Multiple Choice, continued
6. crop milk : crop :: song :
F. syrinx
G. trachea
H. proventriculus
J. anterior air sacs
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Chapter 42
Standardized Test Prep
Multiple Choice
The diagram below shows the digestive system of a
bird. Use the diagram to answer the question that
follows.
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Chapter 42
Standardized Test Prep
Multiple Choice
7. Which digestive structure grinds food, aided by
stones swallowed by the bird?
A. 1
B. 2
C. 3
D. 4
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Chapter 42
Standardized Test Prep
Multiple Choice
7. Which digestive structure grinds food, aided by
stones swallowed by the bird?
A. 1
B. 2
C. 3
D. 4
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Chapter 42
Standardized Test Prep
Short Response
Each type of feather on a bird serves a specific
purpose.
What are the functions of contour feathers and
down feathers in birds?
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Chapter 42
Standardized Test Prep
Short Response, continued
Each type of feather on a bird serves a specific
purpose.
What are the functions of contour feathers and
down feathers in birds?
Answer: Contour feathers streamline the bird’s
body, and down feathers provide insulation.
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Chapter 42
Standardized Test Prep
Extended Response
Base your answers to parts A & B on the
information below.
Imagine that a museum display of bird skeletons
became mixed up, and all of the labels were lost.
Part A How could you separate the skeletons of
flightless birds from those of birds that fly?
Part B How could you tell which birds flew rapidly
and which birds could soar?
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Chapter 42
Standardized Test Prep
Extended Response, continued
Answer:
Part A Sample answer: Flightless bird skeletons
often do not have a keeled sternum. Also, the
skeletons of flightless birds may have a
reduced number of toes and may have a
smaller number of hollow bones.
Part B: Sample answer: Birds that could soar
would have a wider wingspan than birds that
flew rapidly. Birds that flew rapidly would have
shorter wings with respect to their body
length.
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