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A protist (/ ˈ p r oʊ t ɪ s t /) is any eukaryotic organism (one with cells containing a nucleus) that is not an animal, plant, or fungus.The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; [a] but, like algae or invertebrates, the grouping is used for convenience.
Protists are abundant and diverse in nearly all habitats. They contribute 4 gigatons (Gt) to Earth's biomass—double that of animals (2 Gt), but less than 1% of the total. Combined, protists, animals, archaea (7 Gt), and fungi (12 Gt) make up less than 10% of global biomass, with plants (450 Gt) and bacteria (70 Gt) dominating. [166]
Protists are usually single-celled, while plants, fungi and animals are usually multi-celled. It seems very plausible that the root of the eukaryotes lie within archaea; the closest relatives nowadays known may be the Heimdallarchaeota phylum of the proposed Asgard superphylum.
All eukaryotes apart from animals, plants and fungi are considered protists. [1] Its field of study therefore overlaps with the more traditional disciplines of phycology , mycology , and protozoology , just as protists embrace mostly unicellular organisms described as algae , some organisms regarded previously as primitive fungi , and protozoa ...
[3] [4] There has been little research on mixotrophic protists, but recent studies in marine environments found mixotrophic protists contribute a significant part of the protist biomass. [5] Since protists are eukaryotes (and not prokaryotes) they possess within their cell at least one nucleus, as well as organelles such as mitochondria and ...
Protists are distributed across all major groups of eukaryotes, including those that contain multicellular algae, green plants, animals, and fungi. If photosynthetic and fungal protists are distinguished from protozoa, they appear as shown in the phylogenetic tree of eukaryotic groups.
Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly unicellular and microscopic.Many unicellular protists, particularly protozoans, are motile and can generate movement using flagella, cilia or pseudopods.
Photosynthetic plankton species associate with the symbiotes of dinoflagellates, diatoms, rhodophytes, chlorophytes, and cyanophytes that can be transferred both vertically and horizontally. [62] In Foraminifera, benthic species will either have a symbiotic relationship with Symbiodinium or retain the chloroplasts present in algal prey species ...