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Unlike plants, fungi and most types of algae, most protozoa do not have a rigid external cell wall but are usually enveloped by elastic structures of membranes that permit movement of the cell. In some protozoa, such as the ciliates and euglenozoans , the outer membrane of the cell is supported by a cytoskeletal infrastructure, which may be ...
They are the photosynthetic protists, and can be found in most of the main clades, completely intermingled with heterotrophic protists which are traditionally called protozoa. [28] Algae exhibit the most diverse range of morphologies, from single flagellated or coccoid cells (e.g., cryptophytes, haptophytes, dinoflagellates, chromerids, many ...
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 ("animal" motile protists lacking chloroplasts).
Algae (UK: / ˈ æ l ɡ iː / AL-ghee, US: / ˈ æ l dʒ iː / AL-jee; [3] sg.: alga / ˈ æ l ɡ ə / AL-gə) is an informal term for any organisms of a large and diverse group of photosynthetic eukaryotes, which include species from multiple distinct clades.
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.
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 as ...
Predation upon algae is an important driver in alveolate evolution, as it can provide sources for endosymbiosis of novel plastids. The term Myzozoa is therefore a handy concept for tracking the history of the alveolate phylum.
The green algae include unicellular and colonial flagellates, usually but not always with two flagella per cell, as well as various colonial, coccoid, and filamentous forms. In the Charales, which are the algae most closely related to higher plants, cells differentiate into several distinct tissues within the organism. There are about 6000 ...