Two characteristics used to define mammals include
a. mammary glands and scales.
b. mammary glands and hair or fur.
c. mammary glands and sweat glands.
d. sweat glands and a four-chamber heart.

The current thought on the structure of the cell membrane is: a. a static phosphate sandwich of lipids b. a fluid-mosaic of phospholipids and proteins c. a bilayer of proteins with static lipid molecules d. an impermeable bilayer of protein molecules e. a static and permeable phospholipid single layer