| A | B |
|---|
| atrium | each of two upper chambers that receives blood that comes into the heart |
| cartilage | a connective tissue that is more flexible than bone and that gives support to some parts of the body |
| diaphraghm | a large, dome-shaped muscle in a mammal's chest that plays an important role in breathing |
| ectotherm | a radially symmetrical invertebrate that lives on the ocean floor and has a spiny internal skeleton |
| endotherm | an animal whose body controls and regulates its temperature by controlling the internal heat it produces |
| gestation period | the length of time between fertilization and birth of a mammal |
| kidney | a major organ of the excretory system;removes urea, excess water, and other waste from the body |
| mammary glands | the organs that produce the milk with which mammals feed their young |
| marsupial | a mammal whose young are born alive at an early stage of developement and continue to develope in a pouch on their mother's body |
| monotreme | a mammal that lays eggs |
| placenta | a membrane that becomes the link between the developing embryo or fetus and the mother |
| placental mammal | a mammal that developes inside its mother's body until its body systems can function independently |
| ventricle | the lower chamber of the heart, which pumps blood out to the lungs and body |
| vertebra | the bones that make up the backbone |
