Transcript Biology Slide 1 of 50 Copyright Pearson Prentice Hall End Show 32-1 Introduction to the Mammals Slide 2 of 50 Copyright Pearson Prentice Hall End Show.

Biology
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32-1 Introduction to the
Mammals
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32-1 Introduction to the Mammals
Mammals
All mammals have two notable features: hair and
mammary glands.
In females, mammary glands produce milk to
nourish the young.
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32-1 Introduction to the Mammals
Mammals
In addition to having hair and the ability
to nourish their young with milk, all
mammals
• breathe air.
• have four-chambered hearts.
• are endotherms that generate their
body heat internally.
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32-1 Introduction to the Mammals
Evolution of Mammals
The first true mammals appeared during
the late Triassic Period, about 220 million
years ago.
These mammals were very small and
probably nocturnal.
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32-1 Introduction to the Mammals
Reptile / Mammal Skulls
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32-1 Introduction to the Mammals
Form and Function in
Mammals
As mammals evolved, the form and function of
their jaws and teeth became adapted to eat foods
other than insects.
The joint between the skull and lower jaw allowed
mammals to evolve larger, more powerful jaw
muscles and different ways of chewing.
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32-1 Introduction to the Mammals
Form and Function in
Mammals
Jaws and Teeth of Mammals
Carnivore
Herbivore
Canines
Jaw
joint
Wolf
Incisors
Molars and premolars
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Jaw
joint
Horse
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Form and Function in
Mammals
Mammalian
heart
Left atrium
Right atrium
Left ventricle
Right ventricle
Complete
division
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32-1 Introduction to the Mammals
Form and Function in
Mammals
Mammalian
Brain
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32-1 Introduction to the Mammals
Form and Function in
Mammals
The limbs and digits (fingers and toes) of many
mammals are adapted to their particular way of life.
Note the variety of lengths and shapes of the limb
bones. Homologous bones are the same color in
all the drawings.
Monkey
Horse
Mole
Bat
Seal
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32-1
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32-1
One characteristic commonly used to determine
whether fossils are mammals is
a. subcutaneous fat.
b. mammary glands.
c. a jaw joint that allows movement from side to
side.
d. hair or fur.
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32-1
How many chambers do mammalian hearts
have?
a. 2
b. 3
c. 4
d. 6
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Mammals are called endotherms because they
a. produce milk to nourish their young.
b. have well-developed sense organs.
c. have powerful jaws and specialized teeth.
d. generate their body heat internally.
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The first true mammals appeared in the fossil
record
a. soon after the extinction of the dinosaurs.
b. about the same time as the first reptiles.
c. during the Triassic when dinosaurs were the
dominant land animals.
d. long after the extinction of the dinosaurs.
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