32-2 Diversity of Mammals
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32-2 Diversity of Mammals
Diversity of Mammals
The class Mammalia contains about 4500 species.
Mammals have the greatest range of size of any
group of vertebrates.
Tooth structure and the number and kind of bones in
the head are used to classify mammals.
The most important way to categorize living mammals
is by the way they reproduce and develop.
The three groups of living mammals are monotremes,
marsupials, placentals.
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32-2 Diversity of Mammals
Monotremes and Marsupials
Monotremes
Belong to order monotremata
Monotremes, or egg-laying mammals, share two
notable characteristics with reptiles:
• digestive, reproductive, & urinary systems all open
into a cloaca (monotreme means single opening)
• females lay soft-shelled eggs that incubate outside
the body – the eggs hatch in about 10 days
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32-2 Diversity of Mammals
Monotremes and Marsupials
Young monotremes are nourished by their mother's
milk, which they lick from pores on her abdomen.
Only three species of monotremes exist today: the
duckbill platypus and two species of spiny anteaters,
or echidnas.
These animals are found in Australia and New Guinea.
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32-2 Diversity of Mammals
Monotremes and Marsupials
Marsupials
Kangaroos, koalas, and wombats are examples.
Marsupials bear live young, but at a very early stage
of development.
Young marsupials complete their development in an
external pouch.
When marsupials reproduce, the fertilized egg
develops into an embryo inside the mother's
reproductive tract.
The embryo is born at a very early stage
of development.
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32-2 Diversity of Mammals
Monotremes and Marsupials
Once born, the embryo crawls across its mother's fur
and attaches to a nipple.
Nipples are located in a pouch called the marsupium
on the outside of the mother's body.
The embryo spends several months attached to the
nipple.
The young marsupial will drink milk until it grows
enough to survive on its own.
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32-2 Diversity of Mammals
Placental Mammals
Placental Mammals
Mice, cats, dogs, whales, elephants, sea lions, and
humans are examples.
Placental mammals are named for an internal
structure called the placenta, which forms when the
embryo's tissues join with tissues from within the
mother's body.
In placental mammals, nutrients, oxygen, carbon
dioxide, and wastes are exchanged efficiently
between embryo and mother through the placenta.
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32-2 Diversity of Mammals
Placental Mammals
The placenta allows the embryo to develop for a
longer time inside the mother; from a few weeks in
mice to as long as two years in elephants.
Most placental mammals care for and nurse their
young after birth.
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32-2 Diversity of Mammals
Placental Mammals
There are 12 universally agreed upon orders of
placental mammals. Up to 21 have been debated.
Insectivores – order insectivora
•Long, narrow snouts and sharp claws
•Insect eaters
•Tree shrews, hedgehogs, shrews, and moles.
•Very high metabolic rates, eat constantly
•Sharp claws for digging.
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Chiropterans (winged mammals) - Order Chiroptera
• Bats: second largest order, 925 species.
• One quarter of all mammal species.
• Eat all kinds of things, insects, fruit, blood
(vampire bats)
• Night bats use echolocation to find food.
• Many bats live in colonies, sleeping together
upside down with wings wrapped around their
body.
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32-2 Diversity of Mammals
Xenarthrans - Order Edentata
•Means without teeth; simple teeth without enamel, or no teeth
•Sloths, anteaters, armadillos
•Sloth: slow-moving, nocturnal mammal that spends most of its
life hanging upside-down in trees.
•The sloth is an herbivore. The sloth's main defense against
predators is to claw and nip at an attacker.
•Armadillo are timid, armored mammals Armadillos can jump 3
ft straight up into the air. Armadillos have peg-like teeth.
•Anteaters are good swimmers and tree climbers and have a
very long, thin tongue.
•Anteaters walk on their knuckles, and have long, hook-like
claws that do not retract, but curve under the paws when the
anteater walks. They catch insects using their long tongue,
flicking the tongue in and out up to 160 times each minute. 13 Slide
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Rodents - Order Rodentia
• Largest order of mammals: more than 1700 species
• Mice, rats, squirrels, beavers, porcupines,
chipmunks and gophers
• Have two long front teeth, used for chewing. They
grow throughout their life.
• Herbivores
• Short gestation periods
• have a single pair of long, curved incisor teeth
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Lagomorphs - Order Lagomorpha
• Herbivores with two pairs of incisors and hind legs
adapted for jumping
• Rabbits, pikas and hares
• Consists of 65 species
• Sharp front teeth
• Eat plant material
• Short gestation period, produce a lot of young
• Pikas have rounded ears and legs of equal length.
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Carnivores - Order Carnivora
• Have sharp claws and teeth that they use to catch,
kill, and eat prey.
• Meat eaters—exception Panda Bear
• 240 species
• Cats, dogs, wolves, bears, weasels, hyenas, lions,
coyotes and seals
• Sharp teeth and claws
• Strongest and most intelligent groups of mammals
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Order Carnivora, Suborder Pinnipeds
• Walruses, sea lions, otters, and seals
• Swimmers
• Thick layer of fat
• Return to land to reproduce
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Cetaceans - Order Cetacea
• Aquatic Mammals: whales, dolphins, and porpoises
• Must come to the surface to breathe
• Torpedo shaped body with a long pointed head and
no neck
• No gills but have lungs and circulatory system
designed for deep, long dives
• Subcutaneous fat—blubber, for warmth.
• Lost both their external ears and their hind legs
• Bear young in water
• Most are carnivores, some are plankton eaters.
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Sirenians - Order Sirenia
• Large, slow moving mammals that live in aquatic
environments
• Related to the elephant
• Barrel shaped body
• Herbivores
• Live in rivers and streams, some in ocean
• Manatee, sea cow, dugongs
• Inspired legends about mermaids
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Ungulates - Order Artiodactyla
• Hoofed mammals with an even number of toes on
each foot
• Grazing animals
• Cattle, sheep, goats, hippos, giraffes, and pigs.
• Two toes on the foot
• Flat teeth for grinding food
• Have rumen, special structure for to break down
cellulose.
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Placental Mammals
Ungulates - Order Perissodactyla
• Hoofed mammals with an odd number of toes on
each foot
• Horses, zebras, tapirs, and rhinoceroses
• Odd toed ungulates
• Grazers
• Flat teeth for grinding food
• Have rumen, special structure for to break down
cellulose.
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Proboscideans - Order Proboscidea
• Mammals with trunks
• Include the African and Indian elephant
• African elephant is larger and taller and has larger
ears than does the Indian (Asian) elephant.
• Large head broad flat ears, thick skin with little hair
• Boneless trunk transfers food and water to mouth
• Tusks dig up plant roots or pry bark
• Herbivores
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Placental Mammals
Primates - Order Primates
• Highly developed cerebrum and complex behaviors
• 175 species
• Have an opposable thumb: enables them to grasp
branches and other objects.
• Large eyes that face forward
• Omnivores
• Most developed cerebrum and the most
complicated behaviors.
• Live in organized social groups.
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New World Monkeys—live in tees and have long
arms for swinging and they use their prehensile tails
that they use for grasping
Old World Monkeys—Chimps, gorillas: lack tail and
many still enjoy the trees. Humans are also
considered in this group.
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Biogeography of Mammals
Biogeography of Mammals
Earth’s geography has shaped today’s mammals.
During the Paleozoic Era, the continents were one
large landmass, and mammals could migrate freely
across it.
As continents drifted apart during the Mesozoic and
Cenozoic, ancestors of mammal groups were
isolated from one another.
Each landmass took with it a unique array of
mammal groups.
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Biogeography of Mammals
Similar ecological opportunities on the different
continents have produced some striking examples of
convergent evolution in mammals.
Landmasses merged in the late Cenozoic, and
mammals dispersed into new habitats.
Living mammals reflect the diversity that resulted.
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32-2
Most mammals are
a. monotremes.
b. marsupials.
c. placental mammals.
d. placental marsupials.
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32-2
Monotremes are the only group of mammals that
a. lay eggs
b. have hair.
c. feed their young with milk.
d. are endotherms.
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32-2
Rabbits belong to an order of mammals called
the
a. cetaceans.
b. lagomorphs.
c. proboscideans.
d. chiroptera.
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32-2
Ant-eating mammals on different continents look
similar to each other because they are all
a. a result of divergent evolution.
b. adapted to similar ecological opportunities.
c. recently evolved from a common ancestor.
d. evolved from an ant-eating reptile.
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32-2
What is the function of the placenta?
a. production of milk
b. exchange of materials between fetus and
mother
c. digestion of food
d. protection of a young mammal after birth
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