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32-2 Diversity of Mammals
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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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3. Monotremes and Marsupials
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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4. 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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5. Monotremes and 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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6. 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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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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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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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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13. 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.
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15. 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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17. 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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19. 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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21. Order Carnivora, Suborder Pinnipeds
Walruses, sea lions, otters, and seals
Swimmers
Thick layer of fat
Return to land to reproduce
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23. 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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25. 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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27. 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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29. Ungulates - Order Perissodactyla
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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31. 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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33. Primates - Order Primates
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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36. 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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37. 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
monotremes.
marsupials.
placental mammals.
placental marsupials.
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32-2
Monotremes are the only group of mammals that
lay eggs
have hair.
feed their young with milk.
are endotherms.
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32-2
Rabbits belong to an order of mammals called the
cetaceans.
lagomorphs.
proboscideans.
chiroptera.
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32-2
Ant-eating mammals on different continents look similar to each other because they are all
a result of divergent evolution.
adapted to similar ecological opportunities.
recently evolved from a common ancestor.
evolved from an ant-eating reptile.
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32-2
What is the function of the placenta?
production of milk
exchange of materials between fetus and mother
digestion of food
protection of a young mammal after birth
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