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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]
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.
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 ...
The term protist came into use historically as a term of convenience for eukaryotes that cannot be strictly classified as plants, animals or fungi. They are not a part of modern cladistics because they are paraphyletic (lacking a common ancestor for all descendants). Most protists are too small to be seen with the naked eye.
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.
Diaphoretickes (/ ˌ d aɪ. ə f ə ˈ r ɛ t ɪ k iː z / DY-ə-fə-RET-i-keez) is a major group of eukaryotic organisms, with over 400,000 species. The majority of the earth's biomass that carries out photosynthesis belongs to Diaphoretickes. [1]
Marine microorganisms have been variously estimated to make up about 70%, [4] or about 90%, [5] [6] of the biomass in the ocean. Taken together they form the marine microbiome. Over billions of years this microbiome has evolved many life styles and adaptations and come to participate in the global cycling of almost all chemical elements. [7]
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.