You protozoa they are unicellular, eukaryotic organisms that present heterotrophic nutrition. Despite being a widely used term, it has no taxonomic value and is therefore considered an artificial grouping.
The vast majority of protozoa have free life and are found in different aquatic and wet environments. There are, however, species that live in association with other organisms, as is the case with parasites.
Between the human diseases caused by protozoa, we can quote the amoebiasis, trichomoniasis, toxoplasmosis, leishmaniasis (visceral and integument), Chagas disease and malaria.
Protozoa present reproduction asexual with binary division, but there are some species that exhibit sexual reproduction. In the latter case, there is a fusion of these organisms, the formation of a zygote and a subsequent division. This process guarantees genetic recombination. Another form of recombination is conjugation, which is considered by some authors as a type of sexual reproduction. Other protozoa are capable of producing spores that spread through the environment.
→ classification of living beings
A very common type of classification of protozoa uses as a criterion the way of locomotion of these beings in the aquatic environment. According to this system, there are ciliated, flagellate, rhizopod and sporozoan protozoa.
Note the above protozoa and their different locomotion structures
You ciliated protozoa are those that move by the aid of structures called cilia, such as the Paramecium. You flagellated, in turn, use flagella as a means of locomotion, such as the Trypanosoma cruzi, cause of Chagas disease.
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There are also protozoa that move with the help of pseudopods, which are cytoplasmic extensions that modify the body's shape and promote locomotion. This group, which the amoebas are part of, is called rhizopods.
You sporozoans, in turn, do not have any type of locomotor structure and are carried, in the form of spores, by air, water and even by animals. As an example of this group, we can mention the Plasmodium vivax, responsible for causing the malaria.
→ Some phyla of the Protoctist Kingdom
Protozoa have a very controversial and complex classification. Currently, some researchers classify these beings into dozens of different phyla within the Protoctist Kingdom. As these classification systems are unfeasible for laymen to study, many textbooks consider only six main phyla. Are they:
→ Phylum Rhizopoda: refers to rhizopod protozoa, that is, which move by pseudopods.
Amoebas are included in the Rhizopoda phylum.
→ Actinopoda phylum: refers to protozoa that have locomotion by pseudopods, but with this structure in a tapered shape.
→ Phylum foraminifera: It includes protozoa that have a carapace outside the cell, rich in perforations from which pseudopods come out.
→ Aplicomplex phylum: refers to sporozoan protozoa, that is, they have no means of locomotion.
→ Phylum Zoomastigophora: It includes protozoa that have flagella as a locomotor structure.
→ Phylum Ciliophora: It encompasses ciliated protozoa, that is, they have cilia as a means of locomotion.
By Ma. Vanessa dos Santos
Would you like to reference this text in a school or academic work? Look:
SANTOS, Vanessa Sardinha dos. "Protozoa"; Brazil School. Available in: https://brasilescola.uol.com.br/biologia/protozoarios.htm. Accessed on June 27, 2021.
