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Chapter 35
Mammals
Table of Contents
Section 1 The Mammalian Body
Section 2 Today’s Mammals
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Chapter 35
Section 1 The Mammalian Body
Objectives
• Describe three functions of hair.
• Relate a mammal’s teeth to its diet.
• Summarize how mammals maintain a high body
temperature.
• Relate the characteristics of mammals to one
mammal, the grizzly bear.
• Describe parental care in mammals.
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Chapter 35
Section 1 The Mammalian Body
Key Characteristics of Mammals
• Almost all of today’s large, land-dwelling vertebrates
are mammals.
• Mammals are well-adapted for terrestrial living. They
are able to retain water more efficiently than reptiles.
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Chapter 35
Section 1 The Mammalian Body
Characteristics of Mammals
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Chapter 35
Section 1 The Mammalian Body
Key Characteristics of Mammals, continued
Hair
• Of all animal species, only mammals have hair. A
hair is a filament composed mainly of dead cells filled
with the protein keratin.
• The primary function of hair is insulation. The hair of
some mammals helps them blend in with their
surroundings. In some mammals, specialized hairs
serve a sensory function.
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Chapter 35
Section 1 The Mammalian Body
Mammalian Teeth
• Mammals have only two sets of teeth throughout their
lives: baby teeth or milk teeth, then permanent teeth.
• Mammals have four kinds of teeth: incisors, canines,
premolars, and molars.
• A mammal’s teeth are specialized for the food it eats.
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Chapter 35
Section 1 The Mammalian Body
Body Temperature
• Like birds, mammals are endotherms. They can be
active at any time of day or night. They can also live
in cold climates.
• A mammal must eat about 10 times as much food as
an ectotherm of similar size. Mammals have a high
metabolic rate and require considerable amounts of
oxygen.
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Chapter 35
Section 1 The Mammalian Body
Body Temperature, continued
Respiratory System
• Mammalian lungs are more efficient at obtaining
oxygen than are reptilian and amphibian lungs.
• Mammalian lungs contain alveoli, small chambers
that provide a very large surface area.
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Chapter 35
Section 1 The Mammalian Body
Mammalian Lungs
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Chapter 35
Section 1 The Mammalian Body
Body Temperature, continued
Heart and Circulatory System
• Mammals have a four-chambered heart. A septum
completely divides the ventricle into two pumping
chambers.
• One chamber pumps oxygen-rich blood to the body.
The other chamber pumps oxygen-poor blood to the
lungs. The two kinds of blood do not mix.
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Chapter 35
Section 1 The Mammalian Body
External Structures of a Grizzly Bear
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Chapter 35
Section 1 The Mammalian Body
Internal Structures
of a Grizzly Bear
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Chapter 35
Section 1 The Mammalian Body
Parental Care
• Mammals nourish their young with milk. Milk is
produced by mammary glands located on the
female’s chest or abdomen.
• Young mammals are nourished on milk from birth
until weaning, the time when the mother stops
nursing them.
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Chapter 35
Section 2 Today’s Mammals
Objectives
• Recognize how mammals are adapted to different
environments.
• Compare reproductive patterns in monotremes,
marsupials, and placental mammals.
• Relate the distribution of monotremes and
marsupials to the breakup of Pangaea.
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Chapter 35
Section 2 Today’s Mammals
Mammalian Diversity
• Mammals are more diverse in size, anatomy, and
habitat than all other vertebrate groups.
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Chapter 35
Section 2 Today’s Mammals
Comparison of Bats and Whales
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Chapter 35
Section 2 Today’s Mammals
Reproduction
• All mammals reproduce by internal fertilization.
• Mammals are divided into three groups based on
differences in how and where the fertilized egg
develops.
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Chapter 35
Section 2 Today’s Mammals
Reproduction, continued
Monotremes
• The monotremes (order Monotremata) are the most
primitive of all mammals. Among living mammals,
only monotremes reproduce by laying eggs.
• There are three living monotreme species: the
duckbill platypus and two species of echidnas.
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Chapter 35
Section 2 Today’s Mammals
Reproduction, continued
Marsupials
• The marsupials (order Marsupialia) include
kangaroos, koalas, and opossums.
• In marsupial mammals, the young are born
incompletely developed. They crawl to their mother’s
nipples located in a pouch on her abdomen, then
continue their development for several months.
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Chapter 35
Section 2 Today’s Mammals
Reproduction, continued
Placental Mammals
• The young of placental mammals develop within the
female’s uterus. The placenta enables the diffusion
of nutrients and oxygen from the mother to the fetus.
The period of time between fertilization and birth is
called the gestation period.
• Most domestic animals (such horses, cattle, dogs,
and cats) are placental mammals.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals
• There are 19 orders of placental mammals, which
include more than 90 percent of all mammal species.
• The vast majority of mammal species are found
within 12 orders.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 1: Order Rodentia
• About 40 percent of all mammal species are rodents.
Rodents have teeth that are specialized for gnawing.
• Most rodents are small in size. Rodents have a rapid
rate of reproduction.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 2: Order Chiroptera
• This order is composed of bats, the only mammals
capable of true flight. Most bats live in groups and are
active only at night.
• Most bats eat insects, using echolocation to catch
insects while in flight.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 3: Order Insectivora
• This order consists of small mammals, such as the
shrew, that eat mainly insects.
• Insectivores are the mammals most similar to the
ancestors of the placental mammals.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 4: Order Carnivora
• Most species in this order are flesh-eating hunters.
• Carnivores consist of two subgroups: the cat family
and the dog family.
• Carnivores have excellent senses of smell, vision,
and hearing.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 5: Order Pinnipedia
• This order of marine carnivores includes seals and
sea lions.
• All four limbs of pinnipeds are modified as flippers for
swimming. Their bodies are streamlined for rapid
movement through the water.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 6: Order Primates
• Humans belong to the order Primates.
• Other members of this order include the prosimians,
monkeys, and apes.
• Most nonhuman primates are tree-dwellers.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 7: Order Artiodactyla
• Mammals belonging to this order and the following
order, Perissodactyla, are ungulates, mammals with
hooves. Artiodactyls have an even number of toes.
• Many artiodactyls have a stomach with a storage
chamber called a rumen. Mammals with a rumen
regurgitate partially digested food, called cud,
rechew it, and swallow it again for further digestion.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 8: Order Perissodactyla
• Ungulates with an odd number of toes within their
hooves are classified as perissodactyls. This order
includes horses, zebras, and rhinoceroses.
• Perissodactyls lack a rumen and do not chew their
cud.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 9: Order Cetacea
• Cetaceans are divided into two groups: the predatory
toothed whales, dolphins, and porpoises, and the
filter-feeding baleen whales.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 10: Order Lagomorpha
• This order is composed of rabbits and hares. Like
rodents, lagomorphs have long, continually growing
incisors. They also have another pair of incisors that
grow behind the first pair.
• Rabbits and hares have long hind legs and are
specialized for hopping.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 11: Order Sirenia
• Sirenians include dugongs and manatees, barrelshaped marine animals that eat aquatic plants. They
have front limbs modified as flippers.
• Sirenians are closely related to elephants and are
often called sea cows.
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Chapter 35
Section 2 Today’s Mammals
Modern Placental Mammals, continued
Order 12: Order Proboscidea
• There are two living species in this order, the African
elephant and the Indian elephant. These animals are
the largest land animals alive today.
• An elephant’s upper incisor teeth are modified into
long ivory tusks.
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Chapter 35
Standardized Test Prep
Multiple Choice
Use the drawing below and your knowledge of science
to answer questions 1–3.
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Chapter 35
Standardized Test Prep
Multiple Choice, continued
1. Which organisms in structure C contribute to the
digestion of plant material?
A.
B.
C.
D.
algae
yeasts
bacteria
tunicates
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Chapter 35
Standardized Test Prep
Multiple Choice, continued
1. Which organisms in structure C contribute to the
digestion of plant material?
A.
B.
C.
D.
algae
yeasts
bacteria
tunicates
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Chapter 35
Standardized Test Prep
Multiple Choice, continued
2. Which statement describes the function of structure
A?
F.
G.
H.
J.
Fertilized eggs are implanted here.
Air is drawn into structure A.
Milk is produced here.
Nutrients and oxygen diffuse to a fetus through
structure A.
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Chapter 35
Standardized Test Prep
Multiple Choice, continued
2. Which statement describes the function of structure
A?
F.
G.
H.
J.
Fertilized eggs are implanted here.
Air is drawn into structure A.
Milk is produced here.
Nutrients and oxygen diffuse to a fetus through
structure A.
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Chapter 35
Standardized Test Prep
Multiple Choice, continued
3. Which statement describes the structure B?
A. Two pumping chambers supply oxygen-rich
blood to the lungs.
B. Two pumping chambers supply oxygen-poor
blood to the lungs.
C. One pumping chamber supplies blood to the
lungs and body organs.
D. One pumping chamber supplies oxygen-poor
blood to the lungs, and one pumping chamber
supplies oxygen-rich blood to the body organs.
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Chapter 35
Standardized Test Prep
Multiple Choice, continued
3. Which statement describes the structure B?
A. Two pumping chambers supply oxygen-rich
blood to the lungs.
B. Two pumping chambers supply oxygen-poor
blood to the lungs.
C. One pumping chamber supplies blood to the
lungs and body organs.
D. One pumping chamber supplies oxygen-poor
blood to the lungs, and one pumping chamber
supplies oxygen-rich blood to the body organs.
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