3.  The three groups of living mammals are the:  -Monotremes (MAHN-oh-treemz)  - Marsupials (mahr-SOO-pee-ulz)  - Placentals  These groups differ by their means of reproduction and development

4. Monotremes Members of the monotremes, or egg-laying mammals, share two notable characteristics with reptiles… Monotremes means “single opening”

5.  In monotremes, the digestive, reproductive, and urinary systems all open into a cloaca that is similar to the cloaca of reptiles.

6.  Reproduction in monotremes resembles reproduction in reptiles more than other mammals.  Like in reptiles, a female monotreme lays soft-shelled eggs that are incubated outside her body, these eggs hatch into young animals in about ten days.

7.  Young monotremes are nourished by their mother’s milk, which they lick from pores on the surface of her abdomen.

9.  Marsupials are mammals that bear live young that usually complete their development in an external pouch  Ex. Kangaroos, Koalas, Wombats  When marsupials reproduce, the fertilized egg develops into an embryo inside the mother’s reproductive tract.

10.  The marsupial embryo is born at a very early stage of development. It crawls across its mother’s fur, goes into its pouch called the marsupium, and attaches to a nipple and feeds on milk until it will be able to survive on its own. (Marsupials are named after the marsupium.)

12. Placental Mammals Placental mammals are animals that you are most familiar with. Ex: Mice, Cats, Dogs, Whales, Humans, Horses, Etc. This group gets its name from an internal structure called the placenta, which is formed when the embryo’s tissues join with tissues from within the mother’s body.

13. In placental mammals, nutrients, oxygen, carbon dioxide, and wastes are exchanged efficiently between embryo and mother through the placenta. The placenta allows the embryo to develop for a much longer time inside the mother. After birth, most placental mammals care for their young and provide them with nourishment by nursing.

14. Examples:

15. Biogeography of Mammals During the Paleozoic Era, the continents were one large landmass, and mammals could migrate freely across it. But as the continents started to drift apart during the Mesozoic and Cenozoic Eras, the ancestors of mammals groups were isolated from one another. Thousands of kilometers apart, mammals have dispersed and adapted to their new habitats

17. Questions #1: What is a marsupials external pouch called? #2: Where do young monotremes obtain milk on their mother’s body? #3:What are the 3 groups of living mammals? #4: The placenta allows the embryo to develop for a much ______ time inside the mother.

18. #5: How to monotremes give birth? #6: A marsupial embryo is born at a very _____ stage of development #7: The earth’s continents began drifting apart during the ________ and early ________ Eras. #8: The ________ is formed when the embryo’s tissues join with tissues from within the mother’s body