DIVERSITY OF MAMMALSChapter 30.2

OBJECTIVES:

1. State the various characteristics of mammals in each of three subgroups.

2. Describe various adaptations that contribute to the diversity of mammals.

Mammal Classification● the Class Mammalia is divided into three subgroups based on reproductive methods

1. Monotremes: mammals that reproduce by laying eggs(duck-billed platypus and echidna - live only in Australia, Tasmania and New Guinea)

● unique features of monotremes include reptilian bone structure in shoulder area, lower body temp than most mammals, a mix of chromosome size (normal, mammal and reptile-small)

2.marsupials: pouched animals with a short gestation period

● immediately following birth, the offspring crawl into a pouch (skin and hair) on the outside of the mother’s body (as early as 8d post fertilization) and continue to develop and be nourished with milk from mammary glands

● marsupials typically live in Australia (and nearby islands) – the opossum is the only marsupial in N America

3.placental mammals: have a placenta (organ that provides food and oxygen to and removes waste and carbon dioxide from the developing young) - give birth to young that do not require further development in a pouch…

placental mammals are represented by 18 different orders…

Order Insectivora (shrews, hedgehogs, moles) smallest mammals, pointed snouts, live underground, insect-eaters

Order Chiroptera (bats) nocturnal, use sonar, adapted for flight, fruit and insect-eaters

Order Primates (monkeys, apes, humans) binocular vision, large brains, most are tree-dwellers, opposable thumbs

Order Xenarthra (anteaters, sloths, armadillos) toothless or peg-like teeth, insect-eaters

Order Rodentia (beavers, rats, woodchucks, marmots, squirrels, hamsters and gerbils) sharp incisor teeth, plant-eaters

Order Logomorpha (rabbits, pikas, hares)● back legs are longer than front, adapted to jumping, incisors continuously grow

Order Carnivora (dogs, cats, wolves, bears, seals, walruses, coyotes, skunks, otters, minks, weasles)● teeth adapted to tear flesh, meat-eaters

Order Proboscidea (elephants)● long trunks, incisors become long tusks, largest land animal

Order Sirenia (manatees and dugongs)● slow moving, big heads, no hind limbs

Order Perissodactyla (horses, zebras, rhinoceroses)● hoofed, odd number of toes, plant-eaters

Order Artiodactyla (deer, antelope, cattle, sheep, pigs, goats, hippopotamus)● hoofed, even number of toes, plant-eaters that chew cud

Order Cetacea (whales, dolphins, porpoises)● front limbs that are flippers, no hind limbs, nostril forms a blowhole