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Microscopic organisms were increasingly constrained in the plant/animal dichotomy. In 1858, the palaeontolgist Richard Owen was the first to define Protozoa as a separate kingdom of eukaryotic organisms, with "nucleated cells" and the "common organic characters" of plants and animals, although he also included sponges within protozoa. [28]
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.
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]
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.
Haeckel's original (1866) conception of the three kingdoms of life, including the new kingdom Protista. Notice the inclusion of the cyanobacterium Nostoc with plants. In 1674, Antonie van Leeuwenhoek, often called the "father of microscopy", sent the Royal Society of London a copy of his first observations of microscopic single-celled organisms ...
Foraminifera (/ f ə ˌ r æ m ə ˈ n ɪ f ə r ə / fə-RAM-ə-NIH-fə-rə; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of Rhizarian protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell (called a "test") of diverse forms and materials.
The Protist kingdom contains species that have been categorized due to the simplicity of their structure and being unicellular. These include protozoa , algae and slime molds . In marine ecosystems, macroalgae and microalgae make up a large portion of the photosynthetic organisms found.
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 Protozoa.