Everything about Protozoa totally explained
Protozoa (in
Greek proto = first and
zoa = animals) are unicellular
eukaryotes, (singular protozoan). While there's no exact definition of the term, most scientists use
protozoan to refer to a unicellular heterotrophic
protist.
The name 'protozoa' is used for the more animal-like single celled organisms like amoebas and ciliates. The term 'algae' is used for the more plant-like micro organisms. But the distinction is often vague. Dinobryon (top image) has chloroplasts for photosynthesis but it can also feed on organic matter. It is even able to swim. Such an organism can neither be animal nor plant. Nowadays, all these unicellular organisms that are neither animals, plants, bacteria or fungi are called 'protists‘.
Characteristics
Protozoa are around 10–50
μm, but can grow up to 1 mm and can easily be seen under a
microscope. Protozoa exist throughout
aqueous environments and
soil. Protozoa occupy a range of
trophic levels. As predators, they prey upon
unicellular or
filamentous algae,
bacteria, and
microfungi. Protozoa play a role both as
herbivores and as
consumers in the decomposer link of the
food chain. Protozoa also play a vital role in controlling bacteria populations and
biomass. As components of the
micro- and
meiofauna, protozoa are an important food source for
microinvertebrates. Thus, the ecological role of protozoa in the transfer of bacterial and algal production to successive trophic levels is important. Protozoa such as the
malaria parasites (
Plasmodium spp.),
trypanosomes and
leishmania are also important as
parasites and
symbionts of
multicellular animals.
Most protozoa exist in 5 stages of life which are in the form of
trophozoites and
cysts. As cysts, protozoa can survive harsh conditions, such as exposure to extreme temperatures and harmful chemicals, or long periods without access to nutrients, water, or oxygen for a period of time. Being a cyst enables parasitic species to survive outside of the host, and allows their transmission from one host to another. When protozoa are in the form of
trophozoites (Greek,
tropho=to nourish), they actively feed and grow. The process by which the protozoa takes its cyst form is called encystation, while the process of transforming back into trophozoite is called excystation.
Protozoa can reproduce by binary fission or multiple fission. Some protozoa reproduce sexually, some asexually, and some both (eg.
Coccidia). An individual protozoan is hermaphroditic.
Another name for protozoa is
Acrita (R. Owen, 1861). It can also be considered
Eukaryotic Cell Functionase
Classification
Protozoa were commonly grouped in the kingdom of Protista together with the plant-like algae and fungus-like water molds and slime molds. In the 21st-century systematics, protozoans, along with ciliates, mastigophorans, and apicomplexans, are arranged as animal-like protists. However, protozoans are neither Animalia nor Metazoa (with the possible exception of the enigmatic, moldy Myxozoa).
Sub-groups
Protozoa have traditionally been divided on the basis of their means of locomotion, although this is no longer believed to represent genuine relationships:
Further Information
Get more info on 'Protozoa'.
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