Polar bears have thick fur that trap air. Air is a poor conductor of heat. This reduces heat loss from the body to the cold surrounding air.

Many fish have streamlined bodies to reduce drag (friction) in water. This allows them to swim faster in order to catch prey or escape from predators.

Elephant seals fight with other males for the right to mate with female seals. Only strong and healthy males get to mate and pass on their genes to the next generation.

During winter, some birds fly to places (seasonal migration) where the temperature is warmer and food is more abundant.