| A | B |
|---|
| endothermy | mammals produce body heat internally through metabolism, body temperature is kept high and nearly constant by controlling metabolism and regulating the loss of heat through body surfaces |
| hair | insulates mammals bodies against heat loss, it also serves as a camouflauge |
| completely divided heart | mammals have a four chambered heart |
| milk | female mammals produce milk to feed their offspring, it contains fats, proteins, and sugars |
| mammary glands | modified sweat glands located on the thorax or abdomen which produce milk |
| single jawbone | the lower jaw of a reptile is composed of several bones but the lower jaw of a mammal is composed of a single bone |
| specialized teeth | teeth in different parts of a mammal's jaw are modified for different functions |
| synapsids | include mammals and their closest relatives |
| therapsids | synapsids that appeared later in the Permian period, this group later gave rise to mammals |
| monotremes | one of the three main groups to which moderm mammals belong to, this group is oviparous, they lay eggs |
| marsupials | the second of the three main groups to which modern mammals belong to, they are viviparous, which means they give birth to live young |
| placental mammals | the third group of three main groups to which modern mammals belong, they are vivparous, but the young are born at a much later stage of development than are marsupial offspring |
| diaphragm | a sheet of muscle below the rib cage, contraction of this muscle during inhalation helps draw air into the lungs |
| incisors | the cutting teeth |
| canines | grip, puncture, and tear teeth |
| premolars | shear, shred, and cut, or grind teeth |
| molars | grind, crush, and cut teeth |
| baleen | thin plates of fingernail thin material that hang from the roof of their mouth |
| rumen | the first chamber of the stomach that contains symbiotic bacteria and other microorganisms , after plant material is chewed and swallowed it enters this area |
| cecum | a large sac that branches from the small intestine and acts as a fermentation chamber |
| echolocation | bats emit high frequency sound waves, which bounce off objects, and then they analyze the returning echoes to determine the size, distance, direction, and speed of the objects |
| pinnipeds | aquatic carnivores such as sea lions, seals, and walruses, have streamlined bodies for efficient swimming |
| ungulates | mammals with hooves |
