Defining Protista

Contributor: Felicia Sabur. Lesson ID: 12009

Do we think of mold, algae, and protozoa as being royal? They do have their own kingdom, and share common traits with plants and animals, but are actually neither. Explore their little world today!


Life Science

learning style
personality style
Grade Level
High School (9-12)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


What do algae, slime molds, and water molds all have in common, besides being unappetizing?

This lesson will give you a brief introduction to the organisms of the Protista Kingdom, one of the six kingdoms of classification.

This kingdom includes organisms like slime molds, water molds, algae, and protozoa. Protists are eukaryotic organisms that are NOT plants, animals, bacteria, or fungi.

Protists can be multicellular or unicellular. Some are heterotrophic, meaning they must find a food source, while other are autotrophic like plants, and can make their own food from sunlight. Protists also vary greatly in size and can be microscopic or very large.


(multi-cellular, eukaryotic)


(multi-cellular, eukaryotic)


(multi-cellualr, eukaryotic)


(eukaryotic, unicellular and multi-cellular)


(unicellular, prokaryotic)


(unicellular, prokaryotic)


There’s no organism that can be classified as a typical protist. They are grouped together in this kingdom because they are all eukaryotes. Organisms that carry out most of their metabolic processes inside their membrane organelles are called eukaryotes.

  • Metabolic process is the organic process (in a cell or organism) that is necessary for life.
  • The organelles are the tiny structures within a cell that carry out specific functions. For more information about the functions of organelles, check out Prokaryotes, Eukaryotes, & Viruses Tutorial: Eukaryotes on the Arizona University website.

Protists are made up of eukaryotic cells, meaning that the nucleus in the cell has a membrane around it, unlike prokaryote bacteria cells that have a nucleoid without a membrane. Organisms in the plant, animal, fungi, and Protista kingdoms all are made of eukaryote cells. Bacteria from the eubacteria and archaebacteria kingdoms are prokaryotic. Are there any other similarities and differences between the two cells pictured below?

cell types

Image by Science Primer (National Center for Biotechnology Information) and vectorized by Mortadelo2005, via Wikimedia Commons, is in the public domain.

Some protists resemble animals in how they get their food source, and they are called protozoa. However, unlike animals, they are unicellular.

The protists that resemble plants are called algae; however, they are somewhat different from plants. They do not have organs like leaves, roots, and stems. Other algae are like fungi, because they decompose dead organisms. These types of protists are also able to move about at some point in their life.

Protists can also affect your health and life. Some protists cause diseases like malaria, while the unicellular algae are responsible for producing a lot of the oxygen in Earth’s atmosphere. Explain to a parent or teacher what eukaryotes are and why the metabolic processes and organelles are important.

In the Got It? section, you will be learning more about malaria, a disease caused by a certain species of protist.

Elephango's Philosophy

We help prepare learners for a future that cannot yet be defined. They must be ready for change, willing to learn and able to think critically. Elephango is designed to create lifelong learners who are ready for that rapidly changing future.