Earthworm

An earthworm is a segmented annelid that lives mainly in soil, burrowing through it and consuming decaying organic matter. Its movement and feeding mix soil and contribute to nutrient cycling.

Peristalsis: A wave-like sequence of muscle contractions that moves material through a tube or propels an animal. Alternating contractions of circular and longitudinal muscles drive an earthworm through soil.
Annelid: A segmented invertebrate in the phylum Annelida, including earthworms, leeches, and bristle worms. Earthworms are members of this segmented animal phylum.
Vermicomposting: The use of earthworms and microorganisms to convert organic waste into nutrient-rich compost. Specialized earthworm systems transform food scraps and other organic residues into castings.
Bioturbation: The mixing and restructuring of soil or sediment by living organisms. Earthworms are major agents of soil bioturbation through burrowing and feeding.
Hydrostatic skeleton: A support system in which fluid pressure inside a body cavity works with muscles to maintain shape and produce movement. Fluid-filled segments provide resistance against which earthworm muscles push.
Metamerism: The division of an animal body into repeated structural units arranged along its length. Earthworm segments repeat muscles and other structures along the body.
Soil structure: The arrangement of soil particles into aggregates and the pore spaces between them. Earthworm burrows and casts alter soil aggregation, aeration, and water movement.
Nutrient cycling: The movement and transformation of nutrients through organisms, soil, water, and the atmosphere. Earthworms accelerate nutrient transformations by consuming litter and depositing casts.
Chaeta: A stiff bristle made of chitin that many annelids use for traction or anchoring. Earthworms grip the soil with tiny chaetae as their segments extend and contract.
Clitellum: A thickened, glandular band on certain annelids that secretes material involved in reproduction. The earthworm's clitellum produces the cocoon that carries its fertilized eggs.

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