THE EVOLUTION OF MAMMALS

HAIR

• All mammals have hair or fur at sometime in their life, even if it's very thin.
• Class Mammalia is the only species on earth that has hair.
• Hair first evolved in a common ancestor and has "been in the family" ever since.
• The main use for hair is insulation.
• Since mammals are warm-blooded, they use hair to maintain homeostasis.

OFFSPRING

• Mammals are the only species that gives birth to live young.
• Mammals are the only animals that feed their young with the mother's milk.

SWEAT GLANDS

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