Worm
2007 Schools Wikipedia Selection. Related subjects: Organisms
A worm is an elongated soft-bodied invertebrate animal. The best-known is the earthworm, a member of phylum Annelida, but there are hundreds of thousands of species that live in a wide variety of habitats other than soil.
Originally the word referred to any creeping or a crawling animal of any kind or size, such as a serpent, dragon, caterpillar, snail, or the like (this old usage is preserved in the name " slowworm", actually a lizard). Over time this broad definition was narrowed to the modern definition which still includes several different animal groups. Major phyla that include worms include:-
- Acanthocephala (spiny-headed worms)
- Annelida (segmented worms)
- Chaetognatha (arrow worms)
- Gnathostomulida (jaw worms)
- Nematoda (roundworms)
- Nematomorpha (horsehair worms)
- Nemertea (ribbonworms)
- Onychophora (velvet worms)
- Platyhelminthes (flatworms)
- Sipuncula (peanut worms)
Other invertebrate groups may be called worms, especially colloquially. Many insect larvae are called "worms", such as the railroad worm, woodworm, glowworm, bloodworm or silkworm.
Worms may also be called helminths, especially in medical or terminology when referring to parasitic worms, especially the Nematoda (roundworms) and Cestoda (tapeworms). Hence " helminthology" is the study of parasitic worms. When an animal, such as a dog, is said to "have worms", it means that it is infested with parasitic worms, typically roundworms or tapeworms.
Worm species differ in their abilities to move about on their own. Many species have bodies with no major muscles, and cannot move on their own. They must be moved by forces or other animals in their environment. Many species have bodies with major muscles that let them move on their own. They are a type of muscular hydrostat.
Earthworms can be used for composting organic material.
The fear of worms is known as scoleciphobia or vermiphobia.
Some species of worms are hermaphroditic, which means they have characteristics of both sexes.