What Are the Different Kinds of Protozoa?

Protozoa are single-cell, heterotrophic (organisms that use organic carbon for growth) or colonial eukaryotes (organisms whose cells contain complex structures enclosed by a membrane). Depending on the species, they range in size from a few to a hundred micrometers, according to Biology Reference. Since protozoa are heterotrophic they are considered similar to animals in that they consume organic compounds.

Facts

• Protozoa means "first animals" according to Biology Reference, and have at least one nucleus (which contains its DNA) and several organelles. Biologists find it difficult to define protozoa because there are so many different types, all of which have very few similarities. Furthermore, protozoa also vary greatly in size, features, shape, and habit.

Features

• Protozoa are found everywhere in the world because they are prevalent in all moist and aquatic environments. Most subsist on bacteria, algae, and other protozoa and in turn are consumed by other organisms. Some protozoa are even found in very inhabitable places such as sewage treatment plants.

  One way that protozoa are categorized is by their movement. According to Biology Reference, protozoa can be separated into categories that include amoebae, ciliates, flagellates, and apicomplexa (formally called sporazoa).

Types

• Amoebae protozoa have the ability to crawl along surfaces using pseudopods (cytoplasm-filled false feet). They are approximately 0.02 to 5 millimeters long, according to Microscopy.

  Ciliates and flagellates use particular organelles (cilia and flagella, respectively) to move the cell through water. Flagella have undulated motion. A cell may have only one or a few flagella. Cilia are much shorter than flagella and move in a boat oar type action to move the cell forward.

  Apicomplexa is a type of obligate parasitic protozoon. This is a large group of protists that consists of an apical complex structure that penetrates the host's cell (therefore it considered parasitic).

Function

• Ciliates are further divided into two categories, peritrichs and suctoria. Peritrichs ciliates have cylindrical or bell-shaped bodies. Some of them are stalked while others are colonial and attached to plants and animals. They are less than 0.25 millimeters long. Suctoria ciliates have sticky tentacles that capture prey and are found on animals and water plants. They are less than 0.7 millimeters long. Flagellates are whip-like cilia that are less than 0.4 millimeters long.

Example

• Certain types of protozoa result in medical situations. For example, amoeba entamoeba histolytica causes dysentery, and flagellate trypanosoma causes African sleeping sickness.