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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]
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 ...
Microfauna (from Ancient Greek mikros 'small' and from Latin fauna 'animal') are microscopic animals and organisms that exhibit animal-like qualities and have body sizes that are usually <0.1mm. [1] [2] Microfauna are represented in the animal kingdom (e.g. nematodes, small arthropods) and the protist kingdom (i.e. protozoans). A large amount ...
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.
In protists, all-or-none action potentials occur almost exclusively in association with ciliary membranes, [100] [101] [102] with the exception of some non-ciliated diatoms. [ 103 ] [ 104 ] Graded potentials occur in amoebae , also for movement control.
Some modern authors prefer to exclude multicellular organisms from the traditional definition of a protist, restricting protists to unicellular organisms. [ 9 ] [ 10 ] This more constrained definition excludes all brown , the multicellular red and green algae , and, sometimes, slime molds (slime molds excluded when multicellularity is defined ...
By 1981, Cavalier-Smith had divided all the eukaryotes into nine kingdoms. [20] In it, he created Chromista for a separate kingdom of some protists. [21] Most chromists are photosynthetic. This distinguishes them from most other protists which lack photosynthesis. In both plants and chromists photosynthesis takes place in chloroplasts.
Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, [8] often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. [ 7 ] [ 9 ] In traditional classification schemes, Amoebozoa is usually ranked as a phylum within either the kingdom Protista [ 10 ] or the kingdom ...