Importance of Protists

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  • 0:01 What Are Protists?
  • 0:41 Plant-Like Protists
  • 1:53 Animal-Like Protists
  • 4:05 Fungus-Like Protists
  • 4:52 Lesson Summary
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Lesson Transcript
Instructor: Robin Monegue Keeler

Robin has taught college microbiology and environmental science. She has two master's degrees: one in environmental microbiology and the other in public health.

In this lesson, you will learn some cool things about protists. By the end of the lesson, you should be able to describe ways in which protists are important to people and the earth.

What Are Protists?

Protists are a strange and diverse group of organisms. They are so strange that scientists have a tough time defining and classifying them. They are not animals, plants, fungi, or bacteria. As a result, taxonomists, scientists that name, describe, and classify organisms, created a special classification to group these misfits: Kingdom Protista. The protists include organisms that are plant-like (such as algae), organisms that are animal-like (such as amoebas), and organisms that are fungus-like (such as slime molds). It turns out that protists from each of these groups are important to life on Earth.

Plant-Like Protists

If you've ever swam in a lake or the ocean, you probably swam with plant-like protists. Most plant-like protists are algae. Algae include multicellular algae, such as kelp, as well as microscopic algae, such as green algae, golden algae, and diatoms. Since nearly all protists are aquatic, and about three-fourths of the earth is covered in water, they occur just about everywhere!

This is important because these microscopic, plant-like organisms are major oxygen producers. Since there are so many of them, they produce around 30% to 50% of all the oxygen on Earth. The next time you take a breath, think of protists.

A second reason plant-like protists are important is because they form the energy base of most marine and freshwater food chains. A food chain shows how organisms get food, and how nutrients and energy are passed up the chain to more complex organisms. Since algae can make their own food from sunlight, carbon dioxide, and water, a process called photosynthesis, they are the foundation of aquatic food chains. They don't have to depend on any other plant or animal to get food and make energy, unlike organisms that are higher up in the food chain.

Animal-Like Protists

Animal-like protists include a number of species that are important as well. They are known as protozoa. All protozoans are unicellular, or are a single cell. Similar to the plant-like protists, protozoa are found in nearly all aquatic habitats. Protozoa play a key role in maintaining the balance of ecosystems. They are an important food source for organisms higher up in food chains. These little beasties like to hang out in the guts of insects and animals, where they help to break down food particles. There are also some protozoans that cause disease in people. Let's take a closer look at some examples.

Protozoans fall into four categories:

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