Chapter 32-2:Diversity of Mammals Chris Dinh Yonathan Andu Andrew Carpenter

Mammalia The class Mammalia contains about 4500 species Very diverse 3 groups of living mammals: Monotremes, marsupials, and placentals Groups differ in means of reproduction and development

Monotremes “Monotreme” means single opening Share two notable characteristics with reptiles: lay eggs and have cloaca Lay soft-shelled eggs that are incubated outside of mother Eggs hatch in about ten days Young are nourished by mothers milk Only three species of Monotremes exist today

Marsupials Marsupials- mammals bearing young that usually complete their development in an external pouch Embryo are born at a very early stage of development Attatch to a nipple found inside a pouch called a marsupium, found in most marsupial species Young spend several months on the nipple until they are ready to survive on their own Include kangaroos, koalas, and wombats

Placentals The kind we are most familiar with! Cats, dogs, lions, etc. Group gets name from an internal structure called the placenta-formed when the embryo’s tissue joins with the tissue from within its mothers body In placental mammals, nutrients, oxygen, carbon dioxide, and wastes are exchanged between the embryo and mother with the placenta This allows embryos to develop longer

Orders of Placental Mammals There are 12 orders of placental mammals: Insectivores- insect eaters that have long narrow snouts and sharp claws well suited for digging (shrews, hedgehogs) Sirenians- herbivores that live in rivers, bays, and warm coastal waters scattered throughout most of the world (manatee) Cetaceans- adapted to underwater life yet must come to the surface to breathe (whales, dolphins) Chiropterans- winged mammals, the only mammals capable of flight (bats) Rodents- single pair of long, curved incisor teeth in both upper and lower jaw, used for gnawing wood and other hard plant material (rats, squirrels) Perissodactyls- hoofed animals with an odd number of toes on each foot (horses, tapirs, zebras)

Orders cont. Carnivores- stalk or chase their prey by running or pouncing, then kill the prey with sharp teeth (dogs, bears) Artiodactyls- hoofed mammals that have even number of toes on each foot, mostly consists of large grazing animals (giraffes, camels) Lagomorphs- herbivores that have two pairs of incisors, one pair on both jaws, and have hind legs adapted for leaping (rabbits) Xenarthrans- have simple teeth without enamel, some with no teeth at all (sloth, armadillo) Primates- have highly developed cerebrum and complex behaviors (lemurs, apes) Proboschideans- Mammals with trunks (elephant)

Biogeography of Mammals Earth’s geography helped shape mammals During Paleozeic Era, the continent was one large landmass where mammals could roam freely Overtime, after the land separated, unique mammal groups did too Similar ecological opportunities on the different continents have produced some striking examples of convergent evolution in mammals

Quiz Q: About how many species of mammals are their? A: 4500 species Q:What are the three groups of mammals? A: Monotremes, Marsupials, and Placentals Q: How many orders of Placentals are there? A: 12