Protozoan

Protozoa are a diverse group of unicellular eukaryotic organisms, many of which are motile. Originally, protozoa had been defined as unicellular protists with animal-like behavior, such as predation and mobility. The group includes the amoebae, which do not have a fixed shape, the flagellates, which have one or more flagella, and the ciliates, which are covered in cilia.

Classification

Protozoa have traditionally been divided on the basis of locomotion. Although this is no longer the preferred method, the older terms are still used.

• Amoebae - Protozoa that move by pseudopodia.
• Flagellates - Protozoa that move by means of one or more flagella.
• Ciliates - Protozoa covered in cilia.
• Sporozoa - Protozoa that do not have organelles for movement.

Habitat and ecology

Protozoa are found in almost every possible habitat. The soil, oceans and freshwater contain millions of protozoa. Many protozoa inhabit the digestive tracts of animals, and some cause diseases such as malaria and sleeping sickness.

Reproduction

Protozoa typically reproduce asexually by binary fission but they also have sexual reproduction. Some protozoa can form cysts, a dormant form, when conditions are unfavorable.

Protozoa and disease

Many protozoa are parasites that can cause disease in humans and other animals. Examples include Plasmodium, which causes malaria, and Trypanosoma, which causes sleeping sickness.

See also

• Microorganism
• Parasitology
• Protist

Protozoan Resources
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