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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. [1] [2] Historically, protozoans were regarded as "one-celled animals".
Virulence factors (preferably known as pathogenicity factors or effectors in botany) are cellular structures, molecules and regulatory systems that enable microbial pathogens (bacteria, viruses, fungi, and protozoa) to achieve the following: [1] [2] colonization of a niche in the host (this includes movement towards and attachment to host cells ...
There are two types of eukaryotic mixotrophs: those with their own chloroplasts, and those with endosymbionts—and others that acquire them through kleptoplasty or by enslaving the entire phototrophic cell. [30] The distinction between plants and animals often breaks down in very small organisms.
Marine life can be roughly grouped into autotrophs and heterotrophs according to their roles within the food web: the former include photosynthetic and the much rarer chemosynthetic organisms (chemoautotrophs) that can convert inorganic molecules into organic compounds using energy from sunlight or exothermic oxidation, such as cyanobacteria ...
Food is directed into the cytostome, and sealed into vacuoles. 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.
Although protist flagella have a diversity of forms and functions, [11] two large families, flagellates and ciliates, can be distinguished by the shape and beating pattern of their flagella. [ 2 ] In the phylogenetic tree on the right, aquatic organisms (living in marine, brackish, or freshwater environments) have their branches drawn in blue ...
They fill essential roles as decomposers and food sources for lower trophic levels, and are necessary to drive processes within larger organisms. Populations of microfauna can reach up to ~10 7 (~10,000,000) individuals per g −1 (0.1g, or 1/10th of a gram) and are very common in plant litter, surface soils, and water films. [ 3 ]
The filter feeders acquire small, suspended food particles or prokaryotic cells and accumulate them by filtration into the cytostome (e.g., choanoflagellates, some chrysomonads, most ciliates); [2] filter-feeding flagellates accumulate particles by propelling them with a flagellum through a collar of rigid tentacles or pseudopodia that act as a ...