Biology / Unit 10 Bio 2303 short lesson, about 20 seconds
Mammal Traits: Hair and Mammary Glands
Captions available
The idea
Mammals are defined by hair or fur at some life stage and by mammary glands producing milk to nourish offspring.
In practice
A nursing mammal's young feed on milk from mammary glands, a trait no non-mammal vertebrate lineage shares.
Where people slip
Hair coverage varies widely among adult mammals, including species with little visible hair, but the trait appears at some stage in every mammal.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Something wrong in this lesson? Flag it · Sources for Biology