Download Section 32.1 Summary – pages 841 - 847

Unit 1: What is Biology?
Unit 2: Ecology
Unit 3: The Life of a Cell
Unit 4: Genetics
Unit 5: Change Through Time
Unit 6: Viruses, Bacteria, Protists, and Fungi
Unit 7: Plants
Unit 8: Invertebrates
Unit 9: Vertebrates
Unit 10: The Human Body
Unit 1: What is Biology?
Chapter 1: Biology: The Study of Life
Unit 2: Ecology
Chapter 2: Principles of Ecology
Chapter 3: Communities and Biomes
Chapter 4: Population Biology
Chapter 5: Biological Diversity and Conservation
Unit 3: The Life of a Cell
Chapter 6: The Chemistry of Life
Chapter 7: A View of the Cell
Chapter 8: Cellular Transport and the Cell Cycle
Chapter 9: Energy in a Cell
Unit 4: Genetics
Chapter 10: Mendel and Meiosis
Chapter 11: DNA and Genes
Chapter 12: Patterns of Heredity and Human Genetics
Chapter 13: Genetic Technology
Unit 5: Change Through Time
Chapter 14: The History of Life
Chapter 15: The Theory of Evolution
Chapter 16: Primate Evolution
Chapter 17: Organizing Life’s Diversity
Unit 6: Viruses, Bacteria, Protists, and Fungi
Chapter 18: Viruses and Bacteria
Chapter 19: Protists
Chapter 20: Fungi
Unit 7: Plants
Chapter 21:
Chapter 22:
Chapter 23:
Chapter 24:
What Is a Plant?
The Diversity of Plants
Plant Structure and Function
Reproduction in Plants
Unit 8: Invertebrates
Chapter 25: What Is an Animal?
Chapter 26: Sponges, Cnidarians, Flatworms, and
Roundworms
Chapter 27: Mollusks and Segmented Worms
Chapter 28: Arthropods
Chapter 29: Echinoderms and Invertebrate
Chordates
Unit 9: Vertebrates
Chapter 30: Fishes and Amphibians
Chapter 31: Reptiles and Birds
Chapter 32: Mammals
Chapter 33: Animal Behavior
Unit 10: The Human Body
Chapter 34: Protection, Support, and Locomotion
Chapter 35: The Digestive and Endocrine Systems
Chapter 36: The Nervous System
Chapter 37: Respiration, Circulation, and Excretion
Chapter 38: Reproduction and Development
Chapter 39: Immunity from Disease
Vertebrates
Fishes and Amphibians
Reptiles and Birds
Mammals
Animal Behavior
Chapter 32 Mammals
32.1: Mammal Characteristics
32.1: Section Check
32.2: Diversity of Mammals
32.2: Section Check
Chapter 32 Summary
Chapter 32 Assessment
What You’ll Learn
You will identify the characteristics of
mammals.
You will compare and contrast three
groups of living mammals and examine
their relationships to their ancient
ancestors.
Section Objectives:
• Distinguish mammalian characteristics.
• Explain how the characteristics of
mammals enable them to adapt to most
habitats on Earth.
What is a
mammal?
• Mammals,
like birds,
are
endotherms.
What is a mammal?
• They have hair and produce milk to nurse
their young.
• Mammals also have diaphragms, fourchambered hearts, specialized teeth,
modified limbs, and highly developed
brains.
Mammals have hair
• Like feathers,
mammalian
hair, made out
of the protein
keratin, is also
thought to have
evolved from
scales.
Mammals have hair
• The arrangement of hair provides
insulation and waterproofing and thereby
conserves body heat.
Mammals have hair
• Mammals also have internal feedback
mechanisms that signal the body to cool
off when it gets too warm.
• Mammals cool off by panting and through
the action of sweat glands.
• Panting releases water from the nose and
mouth, which results in a loss of body heat.
Mammals have hair
• Sweat glands help regulate body temperature
by secreting moisture onto the surface of the
skin.
• As the moisture evaporates, it transfers heat
from the body to the surrounding air.
Mammals nurse their young
• Mammals have several types of glands,
which are a group of cells that secrete
fluids.
• They include glands that produce saliva,
sweat, oil, digestive enzymes, hormones,
milk, and scent.
Mammals nurse their young
• Mammals also feed their young from
mammary glands, possibly modified sweat
glands, which produce and secrete milk, a
liquid that is rich in fats, sugars, proteins,
minerals, and vitamins.
Mammals nurse their young
• Mammals nurse
their young until
they are able to
digest and absorb
nutrients from
solid foods.
Respiration and circulation in mammals
• The mammals’ diaphragm helps expand the
chest cavity to aid the flow of oxygen into their
lungs.
Position of
ribs when
exhaling
Position of
ribs when
inhaling
Lungs
when
exhaling
Lungs
when
inhaling
Position of diaphragm
when inhaling
Position of diaphragm
when exhaling
Respiration and circulation in mammals
• A diaphragm is the sheet of muscle located
beneath the lungs that separates the chest
cavity from the abdominal cavity, where other
organs are located.
Position of diaphragm
when inhaling
Position of diaphragm
when exhaling
Respiration and circulation in mammals
• Mammals have
four-chambered
hearts in which
oxygenated
blood is kept
entirely
separate from
deoxygenated
blood.
Right
atrium
Right
ventricle
Left
atrium
Left
ventricle
Respiration and circulation in mammals
• Circulation also removes waste products
from cells and helps regulate body
temperature.
• Blood helps keep a constant cellular
environment, which maintains
homeostasis.
Most mammals have specialized teeth
• Mammals with teeth
have different kinds
that are adapted to
the type of food the
animal eats.
Most mammals have specialized teeth
• The pointed incisors of moles grasp and
hold small prey.
• The chisel-like incisors of beavers are
modified for gnawing.
Most mammals have specialized teeth
• A lion’s
canines
puncture and
tear the flesh
of its prey.
Most mammals have specialized teeth
• Premolars and molars are used for slicing
or shearing, crushing, and grinding.
Most mammals have specialized teeth
• Many hoofed mammals have an adaptation
called cud chewing that enables the
cellulose in plant cell walls to be broken
down into nutrients they can absorb and
use.
• When plant material is swallowed, it
moves into the first two of four pouches in
the stomach where cellulose in the cell
walls is broken down by bacteria.
Most mammals have specialized teeth
• The partially digested food, called cud, is
repeatedly brought back up into the mouth.
Most mammals have specialized teeth
• After more chewing, the cud is swallowed
again and when the food particles are small
enough they are passed to the other stomach
areas, where digestion continues.
Mammals have modified limbs
• Mammal limbs are
adapted for a variety
of methods of food
gathering.
• Primates, for example,
use their opposable
thumb to grasp
objects—including
fruits and other foods.
Mammals can learn
• Mammals can accomplish complex behaviors,
such as learning and remembering what they
have learned.
Mammals can learn
• Primates, including humans, are perhaps the
most intelligent animals.
Mammals can learn
• Chimpanzees, for example, can use tools,
work machines, and use sign language to
communicate with humans.
Mammals can learn
Motor area
Cerebrum
Sensory area
Speech area
Language area
Vision area
Taste area
General
interpretation
area
Intellect,
learning, and
personality
Balance
area
Hearing
area
Brain stem
Cerebellum
A Mammal
Question 1
What two characteristics do mammals have
that no other animal has?
Answer
All mammals have hair and produce milk to
nurse their young.
Question 2
What do scientists believe mammalian hair
evolved from?
A. feathers
B. scales
C. skin
D. keratin
The answer is B.
Like feathers,
hair also is made
out of keratin
which leads
scientists to
believe that hair
evolved from
scales.
Question 3
How do a mammal’s teeth help it obtain food?
Mammals have teeth that are adapted to the type
of food they eat. Canine teeth puncture and tear
the flesh of prey. Premolars and molars are used
for slicing, shearing, and crushing while
incisors are used for gnawing and grasping.
Question 4
Which of the following helps a mammal
take in large amounts of oxygen?
A. glands
B. heart
C. teeth
D. diaphragm
The answer is D, diaphragm.
Diaphragm
Heart
Glands
Teeth
Hair
Mammary
glands
Section Objectives:
• Distinguish among the three groups of living
mammals.
• Compare reproduction in egg-laying,
pouched, and placental mammals.
Mammal Classification
• Scientists place mammals into one of three
subclasses based on their method of
reproduction.
Placental mammals: A great success
• Placental mammals give birth to young that
have developed inside the mother’s uterus
until their body systems are fully functional
and they can live independently of their
mother’s body.
Placental mammals: A great success
• The uterus is a hollow, muscular organ in
which offspring develop.
• Nourishment of the young inside the uterus
occurs through an organ called the placenta
which develops during pregnancy.
Placental mammals: A great success
• The time during which placental mammals
develop inside the uterus is called
gestation.
• Development inside the mother’s body ensures
that the offspring are protected from predators
and the environment during the early stages of
development.
Pouched mammals: The marsupials
• A marsupial is a mammal
in which the young have a
short period of
development within the
mother’s body, followed by
a period of development
inside a pouch made of
skin and hair on the outside
of the mother’s body.
Pouched mammals: The marsupials
• Most marsupials are found in Australia and
surrounding islands.
• Scientists have found fossil marsupials on the
continents that once made up Gondwana.
• These fossils support the idea that marsupials
originated in South America, moved across
Antarctica, and populated Australia before
Gondwana broke up.
Monotremes: The egg layers
• The duck-billed platypus is a monotreme, a
mammal that reproduces by laying eggs.
• Spiny anteaters, also called echidnas, belong to
this subclass as well.
Monotremes: The egg layers
• Monotremes are found only in Australia,
Tasmania, and New Guinea.
• Only three species of monotremes are
alive today.
Monotremes: The egg layers
• The platypus,
a mostly aquatic
animal, has a
broad, flat tail,
much like that
of a beaver.
• Its rubbery snout
resembles the bill
of a duck.
Monotremes: The egg layers
• The platypus has webbed front feet for
swimming through water, but it also has
sharp claws on its front and hind feet for
digging and burrowing into the soil.
• Much of its body is covered with thick,
brown fur.
Monotremes: The egg layers
• The spiny anteater has
course, brown hair,
and its back and sides
are covered with
sharp spines that it
can erect for
defensive purposes
when threatened by
enemies.
Origins of Mammals
• The first placental mammals appeared in the
fossils record about 125 million years ago.
• Scientists trace the
origins of placental
mammals from a
group of mouse-sized
animals to a group of
reptilian ancestors
called therapsids.
Origins of Mammals
• Therapsids had features of both reptiles and
mammals.
• They existed between 270 and 180 million
years ago.
Origins of Mammals
• The mass extinction of the dinosaurs at
the end of the Mesozoic Era, along with
the breaking apart of Pangaea and changes
in climate, opened up new niches for early
mammals to fill.
• The Cenozoic Era is sometimes called the
golden age of mammals because of the
dramatic increase in their numbers and
diversity.
Origins of Mammals
Artiodactyls
Cetaceans
220 species
79 species
Carnivores
270 species
Primates
Rodents
230 species
2000 species
Chiropterans
925 species
Perissodactyls
270 species
Insectivores
375 species
Placental
mammals
4400 species
2 species
Marsupials
Therapsids
mammal-like
reptiles
Proboscids
280 species
Reptiles
Amphibians
Fishes
Invertebrates
Species numbers are approximate and subject to change pending discoveries or extinctions.
Monotremes
3 species
Question 1
Which of the following is NOT an
example of a placental mammal?
A. kangaroo
B. human
C. dog
D. fox
The answer is A. A kangaroo is a marsupial.
Question 2
What three events allowed mammals to fill
new niches?
Answer
The mass extinction of the Mesozoic Era, the
break up of Pangaea, and changes in climate
opened up new niches for early mammals to
fill.
Question 3
What is the difference between a monotreme
and a marsupial?
Monotremes reproduce by laying eggs. A
marsupial’s young begins development within
the body but complete its development outside
the body in a pouch made of skin and hair.
Mammal Characteristics
• Mammals are endotherms giving them the
ability to maintain a fairly constant body
temperature.
• Hair is present on all mammals at some
point in their lives.
• Mammals feed their young from modified
sweat glands called mammary glands.
Mammal Characteristics
• Mammals with teeth have different kinds of
teeth that are adapted to the type of food they
eat.
• Highly developed brains enable mammals
to learn.
Diversity of Mammals
• Mammals are classified into three
subclasses—placentals, marsupials, and
monotremes—based on how they reproduce.
• Placental mammals carry young inside the
uterus until their body systems are fully
functional. Nourishment inside the uterus
occurs through an organ called the placenta.
Diversity of Mammals
• Marsupials carry partially developed young
in a pouch on the outside of the mother’s
body.
• Monotremes are egg-laying mammals
found only in Australia, Tasmania, and
New Guinea.
Question 1
How many groups are mammals
classified into?
A. one
B. two
C. three
D. four
The answer is C. Mammals are classified as
placental, marsupial, or as monotremes.
Question 2
Of the teeth shown, which set would most likely
be used by an animal that feeds on grass.
A.
B.
C.
D.
The answer is A. This skull contains primarily
molars and premolars which are used to crush
and grind food.
Question 3
What role do zoos play in the preservation of
endangered species?
Answer
Zoos use captive breeding programs to
increase populations of animals, educate the
public, conduct research, and provide
professional training for staff.
Question 4
Which organ in this mammal is responsible
for keeping oxygenated and deoxygenated
blood separate?
The heart enables mammals to keep oxygenated
and deoxygenated blood separate. This helps
them maintain their high metabolism.
Heart
Question 5
Which of the following is one way that
mammals cool off?
A. by swimming
B. by shedding
C. by panting
D. by hibernating
The answer is C.
Mammals cool off
by panting and
through the action
of sweat glands.
Question 6
Why are mammals considered to be one of
the most successful groups of organisms?
Mammals are capable of accomplishing
complex behaviors such as learning and
remembering what they have learned. Mammals
also guard their young and teach them the skills
they need to survive on their own.
Question 7
While walking through the forest, you find an
animal skull. You notice that the teeth in the
skull are primarily pointed and long. What can
you infer about the diet of the animal?
The animal was most likely a carnivore. Long,
pointed incisors and canines are used to stab
and tear flesh.
Photo Credits
• Digital Stock
• PhotoDisc
• Bill Tarpenning/USDA
• Digital Vision
• Alton Biggs
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