Movement Versus Locomotion
Movement is the change in position of a part of the body, such as blinking an eye, waving a hand or the beating of the heart. Locomotion is the movement of the whole organism from one place to another, such as walking, swimming, flying or crawling. All locomotion involves movement, but not all movement is locomotion.
Key idea
Locomotion = the whole body travels to a new place. Movement of just one part (a nod, a heartbeat) is NOT locomotion.
How Locomotion Happens
In animals with a skeleton, locomotion depends on antagonistic muscles pulling on the skeleton across joints. Muscles contract to pull bones, the bones act as levers, and the coordinated action moves the body forward. Different animals are adapted for locomotion in their environment:
- Fish: a streamlined body and muscle blocks that flex the body and tail from side to side, with fins for steering and balance.
- Birds: light bones, powerful flight muscles and wings that push against the air.
- Humans: an upright endoskeleton with strong leg muscles for walking and running.
Why Locomotion Is Useful
Locomotion lets animals find food, escape predators, search for mates and move to better conditions. Because plants do not move from place to place, they respond instead by slow growth movements (tropisms).
Example
When a fish swims, blocks of muscle on each side of the body contract in turn (an antagonistic action), bending the body from side to side. This pushes water backward, and the water pushes the fish forward.
Remember
Heartbeat and chewing are movements; walking and swimming are locomotion.