Modified photo. Click here for original
Class Mammalia
From some of the smallest bats to the largest whales, Class Mammalia has a diverse range of organisms. Characteristics which unite mammals include having hair, three middle ear bones, and milk-producing mammary glands. Temperature is regulated internally with blood being pumped by a four-chambered heart. All mammals are viviparous (give birth to live young) except monotremes (which lay eggs).