As of 2015, there are about 34,000 known worm species in the world, including about 2,700 kinds of earthworms. Most worms are small, but the largest species, the African giant earthworm, can be up to 22 feet in length. Most worms have long, thin bodies with no legs.
Worms breath through their skin, and the moist feel of their bodies helps them collect oxygen. They move on the ground or through the soil by the hairs or bristles that cover their bodies. Worms feed on organic waste, soil and minerals, and may eat their weight in food. They are beneficial to gardeners and farmers because they also produce excrement that equals their weight on a daily basis, which fertilizes the soil, and they also help crops by loosening the soil as they burrow through the ground.
Each worm possesses both female and male reproductive cells, but each still needs another worm in order to produce offspring. Worms later lay eggs, and upon hatching the young may live for up to 10 years, depending on the species.
Worms, for their size, are about 1,000 times stronger than people in relative terms. They are also hardy creatures; one half of a worm severed into two pieces can survive.