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 • Rodents
– Eat insects – More than one-third of
– Most are small with mammal species are
long pointed noses rodents
– Include moles, shrews, – Include squirrels,
and hedgehogs mice, porcupines
14. • Rabbits, Hares, and • Flying Mammals
Pikas – Bats are the only
– Have sharp, gnawing mammals that fly
teeth – Most use echoes to
– Have 2 sets of incisors find their food and they
in their upper jaw way
– Shorter tails than
rodents
15. • Carnivores • Trunk-Nosed
– Have large canine Mammals
teeth and special – Elephants are the only
molar teeth for slicing living mammals with a
meat trunk
– Many only eat meat – A trunk is a
– Includes bears, cats, combination of an
dogs, otters, hyenas upper lip and nose
16. • Hoofed Mammals • Cetaceans
– A hoof is a thick, hard – All cetaceans live in
pad that covers a the water
mammal’s toe – Unlike fish, they have
– Most hoofed mammals lungs and nurse their
are fast runners young
– Includes giraffes, – Includes whales,
camels, pigs dolphins, and
porpoises
17. • Manatees and • Primates
Dugongs – Have 5 fingers on
– Smallest group of each hand and 5 toes
mammals that live in on each foot
the water – Considered highly
– Used their front intelligent animals
flippers and tail to – Includes monkeys,
swim slowly 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
