protozoai

Protozoa is a broad classification for a diverse group of eukaryotic microorganisms. Historically, "protozoa" was a kingdom within the Linnaean system, but it is no longer considered a formal taxonomic rank. Instead, these organisms are now distributed across various groups within the domain Eukarya, often residing in phyla like Protista, or within more specific classifications like Alveolata, Amoebozoa, and Excavata. The defining characteristic of protozoa is that they are single-celled organisms that are not fungi, plants, or animals.

Protozoa exhibit a wide range of lifestyles. Many are free-living, found in aquatic environments such as oceans, freshwater, and soil, where they play crucial roles as consumers in food webs. Others are parasitic, living in or on other organisms and often causing disease. Their modes of nutrition vary significantly; some are heterotrophic, consuming other organisms or organic matter, while a few exhibit photosynthetic capabilities, akin to algae.

Reproduction in protozoa can occur asexually, through processes like binary fission, or sexually, involving the exchange of genetic material. Their cellular structure is complex, with specialized organelles performing various functions. Locomotion is achieved through different means, including flagella (whip-like appendages), cilia (short, hair-like structures), or pseudopods (temporary extensions of the cell membrane). Examples of protozoa include amoebas, paramecia, and Plasmodium, the parasite responsible for malaria.