Mammals are classified into several groups based on how their young develop. Marsupials carry their young in pouches after they are born. Monotremes lay eggs that hatch outside the body. Placental mammals exchange nutrients between the mother and embryo through the placenta. There are many types of placental mammals including those that live on land or in water, fly, have hooves or trunks. Convergent evolution has led to similar structures developing in different mammals living in similar climates.

1. Mammals Dalton Settles Period 6 March 31, 2010

2. Marsupials Their young develop in a pouch. After growing inside the pouch, the young are forced to live on their own. The most common marsupials are kangaroos, and opossums.

3. Monotremes Monotremes lay eggs. The eggs are soft shelled and incubated outside the body. There are only three types of monotremes know today. The duckbill platypus and two types of anteaters.

4. Placental Mammals In placental mammals, nutrients, oxygen, carbon dioxide, and wastes are exchanged between the embryo and the mother through the placenta. Insectivores: long narrow snouts and sharp claws that are used for digging. Sirenians: herbivores that live in rivers, bays, and warm coastal waters. These are large slow moving animals.

5. More Placental Mammals Cetaceans: animals that lead a fully aquatic lives but must come to the surface to breathe. Chiropterans: winged mammals, and the only mammals capable of true flight. Rodents: single pair of long curved incisor teeth in both their upper and lower jaw. Perrisodactyls: hoofed animal with an odd number of toes on each foot. Artiodactyls: hoofed animals that have and even number of toes on each foot. Proboscideans: mammals with trunks, like elephants. Xenarthrans: small mammals, most have no teeth.

6. Biogeography There has been convergent evolution around the world because there are many similar climates. Convergent Evolution: the appearance of similar structure in organism of different lines of descent.

7. Bibliography Photograph. Web. <http://soer.justice.tas.gov.au/2003/image/559/ilw/p-platypus_m.jpg>. Web. <http://www.enchantedlearning.com/subjects/mammals/Placental.shtml>. Web. <http://www.sacrs.org.za/ecm21/gallery/giraffe-01300813b.jpg>. Web. <http://www.royalpetclub.com/blog/wp-content/uploads/2010/01/541447Australian-Kangaroo-Posters1.jpg>. Miller, and Levine. Biology . Print