2. The First Mammals
• 280 million years ago, reptiles called
“therapsids” existed, which had
characteristics of both reptiles and
mammals
• True mammals appeared soon after
• They were about the size of mice, were
warm blooded, and were able to hunt at
night because they could maintain their
body temperature
3. Common Characteristics
• Mammals share 7
characteristics:
– 1) Making Milk
• All mammals have
mammary glands, which
are structures that make
milk
• Only mature females
produce milk for their
young
• All milk is made of
sugars, water, proteins,
and fats
4. – (2) Breathing Air
• Mammals use
their lungs to get
oxygen from the
air
• Mammals have a
muscle to help
them get air
called a
diaphragm it
lies at the bottom
of the rib cage
5. – (3) Endothermic
• As oxygen helps
break down a
mammal’s food,
energy is released
• This energy keeps
a mammal warm
• Like birds,
mammals are
endotherms
• Helps them survive
in cold areas
6. – (4) Hair
• Mammals stay
warm by having
hair
• Thick coats are
called fur
• Most mammals
have a layer of
fat under their
skin to keep
them warm
• This fat traps
heat in the body
7. – (5) Specialized Teeth
• Mammals have teeth
with different shapes
and sizes for
different jobs
• Meat-eating
mammals have large
canines to help eat
prey
• Plant-eating
mammals have
larger incisors and
molars to help them
bite and grind plants
8. – (6) Sexual
Reproduction
• Most mammals
give birth to live
young
• Newborn
mammals stay
with at least one
parent until they
are grown
9. – (7) Large Brains
• Mammal’s brain is
much larger than that
of most other animals
of the same size
• Allows mammals to
learn and think
quickly
• Also allows mammals
to respond quickly to
events around them
• Mammal uses its
senses to find out
about the world
10. Placental Mammals
• Placental mammal: embryo develops
inside the mother’s body in an organ
called a uterus
– The placenta attaches the embryo to the
uterus
– Placenta carries food and oxygen from the
mother’s blood to the embryo and carries
wastes away from the embryo
– The time that the embryo develops is called
the gestation period
11.
12. • Living placental mammals
are divided into 11 main
groups that contain 18
orders:
– (1) anteaters,
armadillos, & sloths
• These mammals are
called “toothless
mammals” but only
anteaters have no
teeth
• Most catch insects
with long, sticky
tongues
13. • Insectivores
– Eat insects
– Most are small with
long pointed noses
– Include moles, shrews,
and hedgehogs
• Rodents
– More than one-third of
mammal species are
rodents
– Include squirrels,
mice, porcupines
14. • Rabbits, Hares, and
Pikas
– Have sharp, gnawing
teeth
– Have 2 sets of incisors
in their upper jaw
– Shorter tails than
rodents
• Flying Mammals
– Bats are the only
mammals that fly
– Most use echoes to
find their food and they
way
15. • Carnivores
– Have large canine
teeth and special
molar teeth for slicing
meat
– Many only eat meat
– Includes bears, cats,
dogs, otters, hyenas
• Trunk-Nosed
Mammals
– Elephants are the only
living mammals with a
trunk
– A trunk is a
combination of an
upper lip and nose
16. • Hoofed Mammals
– A hoof is a thick, hard
pad that covers a
mammal’s toe
– Most hoofed mammals
are fast runners
– Includes giraffes,
camels, pigs
• Cetaceans
– All cetaceans live in
the water
– Unlike fish, they have
lungs and nurse their
young
– Includes whales,
dolphins, and
porpoises
17. • Manatees and
Dugongs
– Smallest group of
mammals that live in
the water
– Used their front
flippers and tail to
swim slowly
• Primates
– Have 5 fingers on
each hand and 5 toes
on each foot
– Considered highly
intelligent animals
– Includes monkeys,
apes, and humans
18. • Monotremes
– Mammals that lay
eggs
– Examples: duck-billed
platypus, echidna
• Marsupials
– Mammals that carry
their young in a pouch
– Several species of
marsupials living today
– Examples: koalas,
opposum, kangaroo
