Humans are bipedal, which means they walk on two legs. Animals that walk on four legs are:

Animals swim, walk, crawl, slither, squirm, and even fly through the air. They can catch free rides by attaching themselves to other creatures, or by traveling on drifting logs. There are almost as many different forms of locomotion, or ways of moving, as there are animals in the sea. Animals need to travel to hunt for prey, escape from predators, migrate for the season, or search for a mate.
Humans are bipedal, which means they walk on two legs. Animals that walk on four legs are:
tripedal
quadrupedal
octopedal
Most mammals and reptiles on the planet are quadrupeds, or walk on four legs. Humans are the only mammals that walk completely upright.
Birds bones are specially adapted for flying because they are:
filled with helium.
hollow inside.
made out of paper.
Because it takes a lot of energy to fly, birds have thin, light bones that are hollow inside. They also have fewer bones than most mammals and reptiles.
If a shark stops swimming, it will sink.
Sharks have to keep moving. Unlike most fish, sharks dont have swim bladders, the flexible air-filled cavities in fishes bodies that help them stay afloat.
Animals that do not have legs cannot move.
Snakes have muscular bodies that they use to thrust forward. Some worms use tiny microscopic hairs on their bodies to move from place to place.
Term: Locomotion
Definition: movement from one place to another
Examples of types of movement: walking, running, swimming, flying
Why animals do it: to find food, escape predators, find mates, and breathe underwater