Protists: Definition, Facts, & Benefits

Jenna Mellentine, Danielle Haak
  • Author
    Jenna Mellentine

    Jenna Mellentine is a certified teacher who has relevant experience teaching in the public school system for over 3 years. She has a bachelor's degree in Elementary Education from Western Governors University, and is currently working on a master's degree in Science Education.

  • Instructor
    Danielle Haak

    Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Explore the benefits of protists. Learn the definition of a protist and understand why protists are important. Discover interesting facts about protists. Updated: 08/06/2022

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Protists: Overview

Protists are a kind of life traditionally classified in the kingdom Protista. Newer taxonomic organizations will classify some protists in the kingdom of Chromista, but they are still protists. Most protists are unicellular; however, they can be multicellular organisms. Protists are not plants, animals, or fungi, although certain types of protists will have characteristics in common with these organisms.

Protists are eukaryotes, meaning they have eukaryotic cells. Prokaryotes have prokaryotic cells and include the kingdoms of bacteria and archaea. Eukaryotes include protists, plants, animals, and fungi. While all cells have some structures in common, eukaryotic organisms have structures in their cells that prokaryotic organisms do not. These are specialized structures like a nucleus and organelles. Additionally, some protists have cell walls like bacteria and plants.

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What Do Protists Do?

Protists serve good and bad functions in chemical and nutrient cycling here on Earth. Chemical and nutrient cycling is how all living things and the environment recycle resources available here on Earth for use. Protists serve especially important roles in oxygen production and as decomposers.

One-celled protists live abundantly in the Earth's oceans. These protists live near the ocean surface as autotrophic phytoplanktonic organisms. An autotroph has the ability to make its own food through photosynthesis and is a primary producer in food webs. Plankton is not a specific organism and can be plants, animals, protists, bacteria, and archaea. Not all phytoplankton are protists and can include plants and bacteria. Phytoplanktonic algae that live near the surface of the ocean are protists. It is often mistaken for a plant because of its ability to make oxygen and cell structures such as chloroplasts and cell walls.

All phytoplankton, including phytoplanktonic protists, produce oxygen for Earth. These organisms use solar energy and their special organelles, known as chloroplasts, to photosynthesize and make sugar. Oxygen is produced as a waste product from this process and released back into the environment, where it diffuses into the atmosphere.

Heterotrophic plankton and other organisms eat phytoplanktonic organisms as primary consumers. Heterotrophic plankton can also be protists and are called zooplankton. Not all zooplankton are protists, and many zooplankton are categorized as animals.

Protists that live on land can be found in soils and wooded areas. Decomposers known as slime molds are protists often mistakenly confused with fungi. Slime molds are unicellular organisms that often live in the soil, and when nutrients become scarce they can become multicellular organisms that live in a fruiting body or colony-like structure. This is when they are often spotted and confused with mushrooms.

Some protists are not good for nutrient cycling or human benefit and cause disease. A well-known example of such a protist is the parasite that causes malaria. This is caused by the protist, Plasmodium Protozoa.

Why Are Protists Important?

Plant-like protists are important to life on Earth as oxygen producers. Protists that live in the ocean are plant-like plankton, known as algae. These algae are unicellular organisms such as diatoms and dinoflagellates. These organisms contain chloroplasts in their cell, like plants. In turn, they produce oxygen. It is estimated that at least half and possibly more of the oxygen on Earth is produced in the ocean by phytoplanktonic organisms. These protists contribute to that oxygen production along with other phytoplanktonic organisms like plants and bacteria that can photosynthesize.

Some protists benefit from mutually beneficial symbiotic relationships. Dinoflagellates have a symbiotic relationship with coral. They inhabit the coral structure, and this gives the dinoflagellate algae protection and shelter. Coral benefits from the algae supplying both the coral organisms and themselves with nutrients.


White coral polyps are seen with hints of green from the dinoflagellates inside from their symbiotic relationship.

Dinoflagellates brighten white coral polyps from the inside through a symbiotic relationship.


Benefits of Protists

Protists are not only beneficial to the environment as nutrient cycling processors but beneficial to humans as well. Protists benefit the environment by taking on the role of decomposers. In this way, nutrients are recycled back into the environment and food web for other organisms to use. Humans consume some protists for food, and can even use them as medicine to treat some diseases.

How Are Protists Helpful In Our Environment?

Protists are helpful to the environment as oxygen producers and as nutrient and chemical recyclers.

Photosynthetic protists produce oxygen through photosynthesis. Like plants, these protists have chloroplast organelles with chlorophyll pigments that absorb solar energy. They use this solar energy and intake carbon dioxide to make sugar to store energy. Oxygen is a product of the reaction. Additionally, these protists are a large part of the oceanic food web and are consumed by heterotrophic organisms like zooplankton, fish, shrimp, mussels, and even whales.

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Frequently Asked Questions

How are protists important to humans?

Protists can benefit humans in overlooked ways. If a manufacturer uses carrageenan in its ice cream, it may be more pleasing to consume because of the emulsified texture. Additionally, protists can be used for advancement in medicines with afflictions like arthritis and high blood pressure.

What are two good things about protists?

Two good things about protists are they help make oxygen and they help decompose. Photosynthetic protists contribute significantly to the amount of breathable oxygen on Earth, while decomposing protists break down nutrients and make them usable for other organisms.

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