Protists Organisms in the Kingdom Protista

Protists are organisms in the kingdom Protista. These organisms are eukaryotes, meaning they are made up of single or multiple cells which all contain a nucleus enclosed by a membrane. The protists are a diverse group of eukaryotes that cannot be classified as animals, plants, or fungi. Organisms in the Protista kingdom include amoebae, red algae, dinoflagellates, diatoms, euglena, and slime molds.

How Protists Are Defined

Protists are defined by how they obtain nutrition and how they move. Protists are typically divided into three categories, including animal-like protists, plant-like protists, and fungus-like protists.

Protists vary in how they move, which can range from cilia, flagella, and pseudopodia. In other words, protists move by microscopic hair that flaps together, by a long tail that moves back and forth, or by extending its cell body, similar to an amoeba.

Nutritionally, protists tend to gather energy in a variety of ways. They can either eat food and digest it inside of themselves, or they may digest outside of their bodies by secreting enzymes. Other protists, like algae, perform photosynthesis and absorb energy from sunlight to make glucose.

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Protista Kingdom of Life

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Animal-Like Protists

Some protists look like animals and are typically referred to as protozoa. Most of these types of protists are made up of a single cell and are similar to animals in nature because they are heterotrophs and able to move around. While they are not considered animals themselves, it is often thought that they may be a shared ancestor. Examples of animal-like protists include:

• Zooflagellates – flagella
• Sarcodines – extensions of cytoplasm (pseudopodia)
• Ciliates – cilia
• Sporozoans

Plant-Like Protists

There is also a large and diverse group of protists that are plant-like and known as algae. While some are single-celled, others like seaweed have multiple cells. For example, one type of protist in the marine environment is Irish moss, which is a species of red algae. More plant-like protists include:

• Dinoflagellates
• Diatoms
• Euglenoids
• Red algae
• Green algae
• Brown algae

Fungus-Like Protists

Lastly, there are fungus-like protists that are also known as molds. These feed on dying organic matter and look like fungi. The major protists in this family include slime molds and water molds. Slime molds can be found on rotting logs and compost while water molds are seen in moist soils and surface waters. Examples of fungus-like protists may include:

• Dictyosteliomycota
• Myxomycota
• Labyrinthulomycota
• Oomycetes

The Benefits to Our World

Protists are important to the world in several ways. You may be surprised to learn that chalk is made from the fossil shells of protists, which is helpful in our classrooms and our children's creativity and play. Additionally, protists produce oxygen which is helpful for the planet.

Many protists have a high nutritional value which can help improve illnesses. Protists like protozoa are used in foods like sushi and are good for our water, as protozoa are used to prey on bacteria and help to clean water for us to use.