View All Pages

TX: Protists Lesson

The Junk Drawer Kingdom

Look at the following picture and see if you can come up with 3 characteristics that all Protists share.

Various types of protists

Did you have any trouble?

Probably so because there is so much diversity among Protists. Kingdom Protista is sometimes called the “junk-drawer” kingdom because organisms get placed here that do not belong to any other kingdom.

Protists

There are dozens of Protist phyla that are currently accepted by scientists. This course will focus on some common, representative phyla.

Before beginning to study the notes on Protists, take a look at the following short video below:

Let's Look at the Kingdom

Protistan Groups

There are 3 groups that we can use to organize Kingdom Protista: (these are not taxa but informal names)

  1. Animal-like (Protozoa)
  2. Plant-like (Algae, or Protophyta)
  3. Fungus-like (Slime Molds and Water Molds) protists

Each group is composed of multiple phyla based on their nutrition and motility.

 

Why Should We Study Protists?

Protists play a crucial role in helping humans to survive on Earth. Here are some reasons to value these "junk drawer" organisms:

  1. Phytoplankton (algae) serves as the basis for many food chains and plays a significant role in the cycling of carbon and oxygen. They produce about half of the oxygen for the planet and maintain a sink of carbon dioxide in the ocean (rather than in our atmosphere, which would warm it).
  2. Some protists serve as major decomposers in ecosystems.
  3. Byproducts from some protists are used in the industry. Carrageenan (from red algae) is used as a thickener or smoothing agent in items such as toothpaste or ice cream.
  4. Chemicals isolated from protists are used in medicines to treat blood pressure or even ulcers.

But they aren't ALL good!

Protists can be harmful to humans as well. This is most notable when they cause disease, but they can cause ecological damage that affects our lives, too.

  1. Protists are parasites for humans (Giardia, Malaria, Amoebic dysentery, African Sleeping Sickness)
  2. Dinoflagellates can cause red tides, or harmful algal blooms, that poison fish and humans as well as deplete oxygen.
  3. Eutrophication occurs when an excess of fertilizer in a body of water causes an algal bloom that depletes the water of oxygen, therefore killing other life.

Protists Challenge and Before You Go

Practice Time! Use the knowledge you learned from the lesson to complete the practice activities below.

Before You Go You Need To Know

 

The following key points are from the explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.

  1. What are some characteristics of Protists?
    • Eukaryotic, may be unicellular or multicellular, may be heterotroph or autotroph
  2. What are the three groups of protists?
    • Animal-like, Plant-like, and Fungi-like
  3. How are protists helpful and harmful to humans?
    • Helpful: phytoplankton (algae) are food for other organisms in the food chain; decomposers; help to make products like toothpaste; and medicines
    • Harmful: cause some diseases in humans; red tides; algae blooms

IMAGES CREATED BY GAVS