What are Protists?

Their Characteristics and Importance

Protist collage
Protist collage, Credit: Wikimedia/148LENIN

Have you ever examined pond water under a microscope? Did you see small organisms gliding around? If so, you saw a protist. Let’s check out these remarkable organisms.

Table of Contents

What is a protist?

The kingdom of Protista contains mainly unicellular organisms. Some are multicellular. They aren’t animals, plants, or fungi. Some protists live in colonies. What else do we know about protists?

What are five characteristics of a protist?

Protists live in damp and watery habitats

Protists live in ponds, puddles, lakes, and the ocean. They live in damp soil and under dead leaves.

Protists are eukaryotic

Protists are eukaryotes , (from the Greek ευ (eu), “good, true,” and κάρυον (karion), kernel) meaning that they have a nucleus an organelle that contains the chromosomes or genetic code. They have other organelles including a cell membrane, vacuoles, and mitochondria.

Protists have extraordinary ways of moving

A flagellum is a long tail that propels a protist through water. A protist can twirl the flagellum to move. A protist can have one, two, or more flagella.

A Euglena with its long flagellum
A Euglena with its long flagellum. Euglena gracilis, Credit: flickr.com/naturalismus

Cilia are tiny hairs covering a protist. Cilia are also used for movement, and work by using a sweeping motion.


Pseudopods, or “false feet,” are used to move some protists like Amoebas. The cell membrane is pushed out and then fills with cytoplasm. This helps the Amoeba glide

The pseudopod of Amoeba Chaos carolinense
The pseudopod of Amoeba Chaos carolinense, Credit: Wikimedia/dr.Tsukii Yuuji

Protists gain energy in various ways

Plant-like protists get energy from sunlight. They use photosynthesis, like plants. These protists have chloroplasts. An example of a plant-like protist is a diatom.


Animal-like protists need to eat plants, animals, or other protists to get their nutrients. One example of an animal-like protist is an Amoeba.


A protist that has both animal and plant-like characteristics is the Euglena. Not only can a Euglena photosynthesize, but it also feeds on other microbes. As a result, this organism is a missing link between plants and animals.

Dog Vomit Slime Mold (Fuligo septica) at Preservation Park in Guelph, Ontario, Canada.
Dog Vomit Slime Mold (Fuligo septica) at Preservation Park in Guelph, Ontario, Canada, Credit: Wikimedia/Ryan Hodnett

Fungus-like protists get energy from decomposition. They absorb nutrients from dead material. A slime mold is a fungus-like protist.

Protists can use sexual or asexual reproduction

Protists have different types of reproduction. Most protists reproduce asexually but can switch to sexual reproduction if needed.


Asexual reproduction is a good way for protists to reproduce, since they may rarely meet protists of the same species. But how does this work? The protist divides itself in two. One gene set will be passed down to each of the offspring. The science term for this process is binary fission.


Protists will also reproduce sexually using egg and sperm cells and the process of fertilization.

What are some examples of protists?

Do you think you could name all the protists? There are over 200,000 known species! Here are a handful to explore.


Amoebas use pseudopods for movement and catching prey. When a pseudopod captures bacteria, digestion happens in the cell. An amoeba lives in warm lakes or rivers.


A Paramecium is a slipper-shaped protist. It moves with cilia. It lives in lakes, streams, and puddles. It eats algae and bacteria for energy.

Different shapes of diatoms. Nesara KM and Bedi CS
Different shapes of diatoms, Credit: Wikimedia/Nesara KM and Bedi CS

Diatoms live in saltwater and freshwater. They photosynthesize for energy. Their shape can be a triangle, a square, or a circle.


A slime mold is found in forests on rotting trees and on soil. It uses dead plants for nutrition. It can live as one cell, or many can join together to form a large colony.

Why are protists important to us?

Phytoplankton—the foundation of the oceanic food chain.
Phytoplankton—the foundation of the oceanic food chain, Credit: Wikimedia/NOAA MESA Project

Let’s focus on some of the benefits of protists. Scientists estimate that phytoplankton creates over 50% percent of the oxygen in earth’s atmosphere. Several estimates put it closer to 70%. Phytoplankton is made up of protists like green algae and diatoms. It is food for crabs, lobsters, small fish, and herring.


Have you eaten seaweed? Seaweed is made of protists. Seaweed can be made into salads, soup, or sushi. People even make butter with it. Carrageenan, a thickening agent produced by red algae, can be found in our ice cream, cottage cheese, chocolate milk, and puddings.


Protists break down dead animals and plants. An example is a slime mold that breaks down dead trees. Later, new plants will grow in this nutrient-rich soil.


Diatoms are used in tooth paste to polish your teeth. How cool is that?


Next time you’re outside by water, grab some in a cup. Look inside the cup to see what’s swimming there. Or bring it to your science class to peek at it under a microscope. You never know what wonderful protists you’ll see!


Unicellular: Describes organisms made of a single cell


Eukaryotes: Organisms made up of cells that each contain a nucleus


Flagella: Thread-like structure that allows a protist to swim or move


Cilia: Hair-like structures that extend from the body of an organism


Pseudopod: A temporary projection of the cytoplasm of a cell


Decomposition: The process where dead organic substances are broken down into simpler matter


Binary fission: A type of reproduction in which the parent cell divides


Phytoplankton: Microscopic marine algae


Organelles: A structure or part of a living cell that has a specific function


Chloroplasts: Organelles of a plant that allow plants to capture the energy from the sun


Fertilization: The act of making fertile. The union of an egg cell and a sperm cell


Cytoplasm: All of the material inside of a cell membrane, except for the nucleus.

Readability: 60


Flesch Kincaid: 6.7

Vidyasagar, Aparna. What Are Protists. February 2, 2022. https://www.livescience.com/54242-protists.htm


Protists Reproduction and Life Cycles. https://www.britannica.com/science/protist/Reproduction-and-life-cycles


Taylor, Lindsey. How Do Protists Reproduce. July 08, 2019. https://sciencing.com/protists-reproduce-4566859.html


NOAA. How Much Oxygen Comes from the Ocean. February 26, 2021. https://oceanservice.noaa.gov/facts/ocean-oxygen.html


Sullivan, Jolee. 10 Types of Seaweed and How to Eat Them. Marcy, 17, 2022.



Adams, Christopher. What Are Phytoplankton and Why Are They Important? April 5, 2021. https://modestfish.com/phytoplankton/

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  • Lisa Endicott

    My passion for science is rooted in my love and curiosity for nature and animals. I have successfully taught biology, health and English as a Second Language classes for 27 years in Madison, Wisconsin. I earned degrees in Biology and Life Science education along with a Masters in reading education from the University of Wisconsin, La Crosse. I completed my English as a Second Language certificate at the University of Wisconsin, Madison. I find teaching most rewarding when students dig deeper into lessons to answer their own questions. I am excited to write for Smore Science to share the extraordinary world of science. Young women, you belong in STEM careers. We need your voices and your talents. Embrace risks and challenge yourselves.