Earth Science

Life on Earth

History of Cenozoic Life

Study Tip
Remember that the Cenozoic Era is also known as the “Age of Mammals.”

Cenozoic Life

The extinction of many species at the end of the Mesozoic left many niches available to be filled.

Study Tip
Remember that the Cenozoic Era is also known as the “Age of Mammals.”
  • Success of mammals is due to several of their unique traits.
  • Mammals are endothermic and have fur, hair, or blubber for warmth
  • Mammals can swim, fly, and live in nearly all terrestrial environments
  • Mammals initially filled the forests that covered many early Cenozoic lands
  • Over time, forests gave way to grasslands, which created more niches for mammals to fill
  • As climate cooled during the ice ages, large mammals were able to stand the cold weather, so many interesting megafauna developed.
  • Giant sloths
  • Saber-toothed cats
  • Woolly mammoths
  • Giant condors
  • Many other animals that are now extinct
saber-toothed cat
The saber-toothed cat lived during the Pleistocene.
  • Many of the organisms that made up the Pleistocene megafauna went extinct as conditions warmed.
  • Some may have been driven to extinction by human activities
Concept Check
  • What are the Pleistocene megafauna and why were they so large?
  • What characteristics do mammals have that allow them to fill so many niches?
  • How does climate affect evolution?