A frog begins as an egg then becomes a tadpole then become an adult frog. Many have a strong muscle know as a foot that is used for movement. Clams and oysters are known as bivalves- they obtain their oxygen and food from the water by gills. They have a heart, blood vessels, and a brain. A typical segmented worm is an earthworm.
Earthworms burrow through the soil and digest dead organic matter.
The tunnels they create allow air, water, and plant matter to enter the soil and keep it loose and rich in nutriments. Leaches are parasitic segmented worms that live in oceans, rivers, and streams. There are more species of insects than all other animal speices combined. They all have a head, thorax. and abdomen. The thorax has three pairs of legs and often one pair of wings.