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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 ...
Many protists reproduce sexually, as do many multicellular plants, animals, and fungi. In the eukaryotic fossil record, sexual reproduction first appeared about 2.0 billion years ago in the Proterozoic Eon, [64] [65] although a later date, 1.2 billion years ago, has also been presented.
Many protist species can switch between asexual reproduction and sexual reproduction involving meiosis and fertilization. [6] In contrast to the cells of prokaryotes, the cells of eukaryotes are highly organised. Plants, animals and fungi are usually multi-celled and are typically macroscopic. Most protists are single-celled and microscopic.
A protist (/ ˈ p r oʊ t ɪ s t / PROH-tist) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus.Protists do not form a natural group, or clade, but are a polyphyletic grouping of several independent clades that evolved from the last eukaryotic common ancestor.
Protistology is a scientific discipline devoted to the study of protists, a highly diverse group of eukaryotic organisms. All eukaryotes apart from animals, plants and fungi are considered protists. [1]
Protists are a large group of diverse eukaryotic microorganisms, mainly unicellular animals and plants, that do not form tissues. [8] The earliest eukaryotes were likely protists. Mating and sexual reproduction are widespread among extant eukaryotes including protists such as Paramecium and Chlamydomonas.
Protists have the advantage of diversifying their modes of reproduction. This is useful for a multitude of reasons. First, if there is an unfavorable change in the environment that puts the ability to deliver offspring at risk, then it is advantageous for an organism to have autogamy at its disposal.
Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. [6] [7] Sexual reproduction also occurs in some unicellular eukaryotes. [2] [8] Sexual reproduction does not occur in prokaryotes, unicellular organisms without cell nuclei, such as bacteria and archaea.