Question

State the use of echo by a bat, dolphin and fisherman.

Answer 1

Bats send out sound waves using their mouth or nose. When the sound hits an object an echo comes back. The bat can identify an object by the sound of the echo. They can even tell the size, shape and texture of a tiny insect from its echo. Most bats use echolocation to navigate in the dark and find food.
Dolphin's echolocation was the result of evolution over time. This process allows them to send out sound waves that are like a click. When those sounds hit an object it bounces back vibrations to the dolphins. This allows them to identify where objects are located. It also gives them information about the location of the object and some indication of the shape and size of it. The amount of time it takes for the sound waves to come back help them to identify the distance. The longer it takes for the sound waves to return, the more distance between them and that given object.
Fishermen's machine sends a loud beep. The machine starts listening again and picks up the echo. This is repeated many times as the fisher moves the boat across the sea. When the echo changes, that means the beep is bouncing off a shoal of fish. So that's the place to drop the nets in.