Mr. Carl's e-Class

Topic:  Protists


What is a Protist? | Animal-like Protists | Fungus-like Protists | Plant-like Protists

What is a Protist?

Protists are organisms that are classified into the kingdom Protista.  The protists form a group of organisms that really do not fit into any other kingdom.  Although there is a lot of variety within the protists, they do share some common characteristics.

All protists are eukaryotic.  That is, all protists have cells with nuclei.  In addition, all protists live in moist environments.

Protists can be unicellular or multicellular.  Protists can be microscopic or can be over 100 meters (300 feet) long.  Some protists are heterotrophs, while others are autotrophs.

Since protists vary so much, we will group them into three subcategories: animal-like protists, fungus-like protists, and plant-like protists.


Animal-like Protists

Protists that are classified as animal-like are called protozoans and share some common traits with animals.  All animal-like protists are heterotrophs.  Likewise, all animal-like protists are able to move in their environment in order to find their food.  Unlike, animals, however, animal-like protists are all unicellular.

Animal-like protists are divided into four basic groups based on how they move and live.

Protists with Pseudopods
Protists with
Protists with
These protists move by extending their bodies forward and then pulling the rest of their bodies forward as well (check it out).  The finger-like structures that they project forward are called pseudopods.  The pseudopods are also used to trap food. These protists move by beating tiny hair-like structures called cilia.  The cilia act as tiny oars that allows the protist to move through its watery environment (check it out).  The cilia also help the protists capture food. These protists move by beating their long whiplike structures called flagella.  These protists can have one or more flagella that help them move.  Many of these protists live in the bodies of other organisms.  Sometimes, they help their host, while at other times they harm their host. These protists are chartacterized mainly by the way they live.  All of these protists are parasites.  Many of these protists cause diseases such as malaria.
The ameba is an example of this type of animal-like protist. The paramecium is an example of this type of animal-like protist. The Giardia is an example of this type of animal-like protist. The Plasmodium is an example of this type of animal-like protist.
Ameba Anatomy
Paramecium Anatomy
Giardia Anatomy and Live Cycle
Life Cycle of Plasmodium

Fungus-like Protists

Fungus-like protists are heterotrophswith cell walls.  They also reproduce by forming spores.  All fungus-like protists are able to move at some point in their lives.  There are essentially three types of fungus-like protists:  water molds, downy mildews, and slime molds.
Water Molds
Downy Mildews
Slime Molds
  • Live in water or moist environments
  • Look like tiny threads with a fuzzy covering
  • Attack food such as potatoes, cabbage, and corn and can destroy whole crops
Water Mold
Domny Mildew
Slime Mold

Plant-like Protists

Plant-like protists are autotrophic.  They can live in soil, on the bark of trees, in fresh water, and in salt water.  These protists are very important to the Earth because they produce a lot of oxygen, and most living things need oxygen to survive.  Furthermore, these plant-like protists form the base of aquatic food chains.

These plant-like protists can be unicellular, multicellular, or live in colonies.  The plant-like protists are divided into four basic groups:  euglenoids, dinoflagellates, diatoms, and algae.

  • Unicellular
  • Glasslike cell walls
    • Used in toothpastes, scouring products, and as filters
Euglenoid Anatomy
Dinoflagellate Anatomy
Diatom Anatomy
Green Algae
Red Algae
Brown Algae
  • Multicellular
  • Commonly called sea weed
  • Live in deep salt water
  • Are used by humans to help make ice cream and hair conditioner
  • Are eaten in some Asian cultures
  • Multicellular
  • Commonly called sea weed
  • Have large leaf-like structures called blades
  • Have air-filled sacs called air bladders
  • Have root-like structure called holdfast
  • Live in salt water
  • Are used by humans to help make pudding and salad dressing
Green Algae
Red Algae
Brown Algae

Check out Mr. Carl's other e-classes.

Bacteria | Viruses | Science Internet Treasure Hunt | Internet Animal Safari | Fungus | Math

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