Fins for water, feathers for flight, thick fur for the cold — an animal’s body is a record of the challenges its ancestors survived.
- Today’s animal diversity results from changes in body structure over long periods .
- Fins and gills let fish move and breathe in water; feathers and hollow bones make flight possible in birds.
- Fat storage in camels, thick fur in polar bears and mammary glands in mammals show how structural features support survival in different environments .