What is Protists? | Types, Definition, Structure, Function & Facts

What is Protists?

Protists are organisms that are part of the biological kingdom known as protists. These organisms are not plants, animals, bacteria or fungi. Protists are a very diverse group of organisms. Basically, these are all organisms that don’t fit into other groups.

Characteristics of Protists

Protists as a group have very little in common. They are eukaryotic microorganisms with a fairly simple eukaryotic cell structure. Also, it is any organism that is not a plant, animal, bacteria, or fungus.

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Types of Protists

One way protists can be divided based on how they move.

  • Cilia – Some protozoa use microscopic hairs called cilia to move around. These tiny hairs can bump against each other to help the organism move through water or other liquids.
  • Flagella – Other protists with a long tail are called flagella. This tail can move back and forth to help propel the creature.
  • Pseudopodia – This is when the protozoa expands part of its cell body to spin or ooze. Amoebas use this method to move.

What do they Eat?

Different protists capture energy in different ways. Some eat food and digest it inside. Others digest food outside of their bodies by secreting enzymes. They then eat pre-digested food. There are still other protists that use photosynthesis like plants. They absorb sunlight and use this energy to make glucose.


One of the main types of protists is algae. Algae are protists that carry out photosynthesis. Algae are very similar to plants. They have chlorophyll and make food using oxygen and energy from sunlight. However, they are not considered plants because they do not have specialized organs or tissues such as leaves, roots, and stems. Algae are often divided based on their color, such as red, brown, and green.

Slime Molds

Slime molds are different from molds. There are two types of molds: cellular and plasmodial.

Plasmodial mold is made of one large cell. They are also called cells. Although these organisms are only one cell, they can be very large, even several feet wide. They can also have multiple nuclei in a cell.

Cellular slime molds are small single-celled organisms that can group together to function as a single organism. Different mobile slime molds will perform different functions when working together.


Amoebas are small single-celled organisms that move by pseudopodia. Amoebas are formless and eat by swallowing food. Amoebas reproduce by dividing into two through a process of cell division known as mitosis.

Interesting Facts about Protists

Many protists act as pathogens for humans. This means they cause disease.

Malaria is caused by the parasite Plasmodium falciparum.

If an amoeba is cut in half, the half with the core will survive, while the other half will die.

The word “pseudopod” comes from the Greek word for “prosthetic leg“.

Seaweed is a type of seaweed that grows in the ocean.