| A | B |
|---|
| members of the three groups of mammals | monotremes,marsupials and placental mammals are classified on the basis of how their young develop |
| marsupials | mammals whose young are born alive, but at an early stage of development, and they usually continue to develop in a pouch on thier mothers body |
| gestation preiod | the length of time between fertilization and birth |
| placental mammmal | develops inside a mother's body until it's body systems can funtion independently |
| placenta | an organ in the pregnant female mammals that passes material between the mother and the developing embryo |
