The Chaetognatha or chaetognaths are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, they are mostly nektonic; however about 20% of the known species are benthic, and can attach to algae and rocks. They are found in all marine waters, from surface tropical waters and shallow tide pools to the deep sea and polar regions. Most chaetognaths are transparent and are torpedo shaped, but some deep-sea species are orange. They range in size from 2 to 120 millimetres.
Hypothesis of the possible homology between the jaw parts of extant and extinct Chaetognathifera taxa. Putative homologies between jaw parts have the same color. Questionable, and/or, disputable homologies are in grey. Only the anterior part of each organism is represented. Modified from Bekkouche and Gąsiorowski 2022.
Comparison of size between various viruses and the bacteria E. coli
In biology, a phylum is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta.
Image: Amoeba proteus
Image: Toxoplasma gondii
Image: Aplanonet 3
Image: Euglypha sp
