Worms
The term /ˈwɜrm/ is used in everyday language to describe many different distantly related animals that typically have a long cylindrical tube-like body and no legs. Worms vary in size from microscopic to over 1 metre (3.3 ft) in length for marine polychaete worms (bristle worms),[1] 6.7 metres (22 ft) for the African giant earthworm,Microchaetus,[2] and 55 metres (180 ft) for the marine nemertean worm (bootlace worm), Lineus longissimus.[3]Various types of worm occupy a small variety of parasitic niches, living inside the bodies of other animals. Free-living worm species may live on land, in marine or freshwater environments, or burrow.
In biology, "worm" refers to an obsoletetaxon (vermes) used by Carolus Linnaeus and Jean-Baptiste Lamarckfor all non-arthropod invertebrate, and stems from the Old Englishword wyrm. Most animals called "worms" are invertebrates, but the term is also used for the amphibian and the slow worm Anguis, a legless burrowing lizard. Invertebrate animals commonly called "worms" include annelids (earthworms),nematodes (roundworms),platyhelminthes (flatworms), marinepolychaete worms (bristle worms), marine nemertean worms ("bootlace worms"), marine Chaetognatha (arrow worms), priapulid worms, and insect such as caterpillars, grubs, andmaggots.
Historical English-speaking cultures have used the (now deprecated) termsworm, Wurm, or wyrm to describecarnivorous reptiles ("serpents"), and the related mythical beasts dragons. The term worm can also be used as an insult or pejorative term used towards people to describe a cowardly or weak individual or individual seen as pitiable.
Distribution and habitat
Worms live in almost all parts of the world including marine, freshwater, and terrestrial habitats. Some worms living in the ground help to condition the soil (e.g., annelids, aschelminths). Many thrive as parasites of plants (e.g., aschelminths) and animals, including humans (e.g., platyhelminths, aschelminths). Several other worms may be free-living, or nonparasitic. There are worms that live in freshwater, and even on the seashore. Ecologically, worms form an important link in the food chains in virtually all theecosystems of the world.
In the United States, the average population of worms per acre is 53,767.[4]
Classification
In everyday language, the term worm is also applied to various other living forms such as larvae, insects,centipedes, shipworms (teredo worms), or even some vertebrates (creatures with a backbone) such as blindwormsand caecilians. Worms can be divided into several groups, but are still technically decomposers.
The first of these, Platyhelminthes, includes the flatworms, tapeworms, andflukes. They have a flat, ribbon- or leaf-shaped body with a pair of eyes at the front. Some are parasites.The second group contains thethreadworms, roundworms, andhookworms. This phylum is calledNematoda. Threadworms may be microscopic, such as the vinegar eelworm, or more than 1 metre (3 feet) long. They are found in damp earth, moss, decaying substances, fresh water, or salt water. Some roundworms are also parasites. The Guinea worm, for example, gets under the skin of the feet and legs of people living in tropicalThe third group consists of the segmented worms, with bodies divided into segments, or rings. This phylum is called Annelida and the bristle worms of the sea.
In earlier taxonomic classification, all the above were included in the now obsolete group Vermes.
There are hundreds of thousands ofspecies that live in a wide variety of habitats other than soil. Over time this broad definition narrowed to the modern definition, although this still includes several different animal groups. Phyla that include worms include:
Annelida (segmented worms)Arthropoda (inchworms, sometimes called "canker worms") (arrow worms)Gnathostomulid (jaw worms)Hemichordata (acorn/tongue worms)Nematoda (roundworms)Nematomorpha (horsehair worms) (ribbonworms)Onychophora (velvet worms)Phoronida (horseshoe worms)Platyhelminthes (flatworms)Priapulida (phallus worms)Sipuncula (peanut worms)
The term /ˈwɜrm/ is used in everyday language to describe many different distantly related animals that typically have a long cylindrical tube-like body and no legs. Worms vary in size from microscopic to over 1 metre (3.3 ft) in length for marine polychaete worms (bristle worms),[1] 6.7 metres (22 ft) for the African giant earthworm,Microchaetus,[2] and 55 metres (180 ft) for the marine nemertean worm (bootlace worm), Lineus longissimus.[3]Various types of worm occupy a small variety of parasitic niches, living inside the bodies of other animals. Free-living worm species may live on land, in marine or freshwater environments, or burrow.
In biology, "worm" refers to an obsoletetaxon (vermes) used by Carolus Linnaeus and Jean-Baptiste Lamarckfor all non-arthropod invertebrate, and stems from the Old Englishword wyrm. Most animals called "worms" are invertebrates, but the term is also used for the amphibian and the slow worm Anguis, a legless burrowing lizard. Invertebrate animals commonly called "worms" include annelids (earthworms),nematodes (roundworms),platyhelminthes (flatworms), marinepolychaete worms (bristle worms), marine nemertean worms ("bootlace worms"), marine Chaetognatha (arrow worms), priapulid worms, and insect such as caterpillars, grubs, andmaggots.
Historical English-speaking cultures have used the (now deprecated) termsworm, Wurm, or wyrm to describecarnivorous reptiles ("serpents"), and the related mythical beasts dragons. The term worm can also be used as an insult or pejorative term used towards people to describe a cowardly or weak individual or individual seen as pitiable.
Distribution and habitat
Worms live in almost all parts of the world including marine, freshwater, and terrestrial habitats. Some worms living in the ground help to condition the soil (e.g., annelids, aschelminths). Many thrive as parasites of plants (e.g., aschelminths) and animals, including humans (e.g., platyhelminths, aschelminths). Several other worms may be free-living, or nonparasitic. There are worms that live in freshwater, and even on the seashore. Ecologically, worms form an important link in the food chains in virtually all theecosystems of the world.
In the United States, the average population of worms per acre is 53,767.[4]
Classification
In everyday language, the term worm is also applied to various other living forms such as larvae, insects,centipedes, shipworms (teredo worms), or even some vertebrates (creatures with a backbone) such as blindwormsand caecilians. Worms can be divided into several groups, but are still technically decomposers.
The first of these, Platyhelminthes, includes the flatworms, tapeworms, andflukes. They have a flat, ribbon- or leaf-shaped body with a pair of eyes at the front. Some are parasites.The second group contains thethreadworms, roundworms, andhookworms. This phylum is calledNematoda. Threadworms may be microscopic, such as the vinegar eelworm, or more than 1 metre (3 feet) long. They are found in damp earth, moss, decaying substances, fresh water, or salt water. Some roundworms are also parasites. The Guinea worm, for example, gets under the skin of the feet and legs of people living in tropicalThe third group consists of the segmented worms, with bodies divided into segments, or rings. This phylum is called Annelida and the bristle worms of the sea.
In earlier taxonomic classification, all the above were included in the now obsolete group Vermes.
There are hundreds of thousands ofspecies that live in a wide variety of habitats other than soil. Over time this broad definition narrowed to the modern definition, although this still includes several different animal groups. Phyla that include worms include:
Annelida (segmented worms)Arthropoda (inchworms, sometimes called "canker worms") (arrow worms)Gnathostomulid (jaw worms)Hemichordata (acorn/tongue worms)Nematoda (roundworms)Nematomorpha (horsehair worms) (ribbonworms)Onychophora (velvet worms)Phoronida (horseshoe worms)Platyhelminthes (flatworms)Priapulida (phallus worms)Sipuncula (peanut worms)
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