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Protozoa (sg.: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris.
The phylum Cercozoa includes many of the most abundant and ecologically significant protozoa in soil, marine and freshwater ecosystems. [ 8 ] Soil-dwelling cercozoans are one of the dominant groups of free-living eukaryotic microorganisms found in temperate soils, accounting for around 30% of identifiable protozoan DNA in arid or semi-arid ...
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.
The group contains free-living and parasitic organisms, predatory flagellates, and photosynthetic organisms. Transmission electron micrograph of a thin section of the surface of the ciliate Paramecium putrinum, showing the alveoli (red arrows) under the cell surface. Almost all sequenced mitochondrial genomes of ciliates and apicomplexa are ...
The Apicomplexa phylum contains several parasitic protozoans. They have a very complex life cycle that includes several stages. They have a very complex life cycle that includes several stages. Megaloschizonts and the smaller schizonts are the part of the life cycle that takes place inside the infected host organism and operates as an asexually ...
For example, protozoa can help maintain the quality of the soil by grazing on soil bacteria. Through their grazing, the protozoa can help maintain populations of bacteria, allowing the bacteria to more efficiently decompose dead organic material which will improve the fertility of the soil .
The Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other taxa. [4] The term Spiralia is applied to those phyla that exhibit canonical spiral cleavage, a pattern of early development found in most (but not all) members of the Lophotrochozoa. [5]
Only certain groups of protozoa, such as the Ciliophora and Excavata, have cytostomes. [1] An example is Balantidium coli , a ciliate. In other protozoa, and in cells from multicellular organisms, phagocytosis takes place at any point on the cell or feeding takes place by absorption.