| A | B |
|---|
| Hair | Used to insulate the body from heat loss. |
| Synapsids | Mammals and their closest relatives. |
| Therapsids | The group of reptiles that gave rise to mammals. |
| Monotremes | Mammals that lay eggs. |
| Marsupials | Mammals that give birth to live young, but the period of development inside the mother is short. |
| Placental mammals | Mammals that give birth to live young after a long period of development inside the mother. |
| Diaphragm | A sheet of muscle below the ribcage, it contributes to the efficiency of respiration in mammals. |
| Incisors | Chisel-like teeth used for cutting. |
| Canines | Pointed teeth used to grip, punture, and tear. |
| Premolars | Teeth used to shear, shred, cut, or grind. |
| Molars | Teeth used to grind, cut, or crush. |
| Baleen | Thin plates of fingernail-like material that hang from the roof of the mouth. |
| Rumen | The first of four chamber in the stomach of some mammals. It contains symbiotic organisms that aid in the digestion fo plants. |
| Cecum | A large sac that branches from the small intestine used to digest plants. |
| Echolocation | Emiting high-frequency sound waves that can be used to determine the size, distance, direction, and speed of objects (prey). |
| Viviparity | When a shell does not form around an egg. |
| Placenta | Formed from membranes within the egg it the gateway between the mother and the embryo and transfers oxygen and nutrients. |
