Single Celled Organisms

Unicellular Organisms Some organisms are made up of only one cell. We call these organisms unicellular which means one-celled. These organisms are much simpler than most organisms that are made up of many cells.

Archea/Eubacteria The Archea/Eubacteria Kingdom consists of unicellular life forms. Prokaryotic cells are far simpler and more basic than the cells of other life forms.

No Nucleus Archea/Eubacteria cells have no nucleus so they are prokaryotes. They are also missing many of the organelles, or parts, commonly found in other cells. For this reason, Archea/Eubacteria are thought to be very distantly related to other life forms. Bacteria is one type of Archea/Eubacteria

Bacteria

Protists The Protista Kingdom consists of unicellular life forms (life forms with only one cell). All protists are eukaryotes – they have a nuclues.

Protist vs Bacteria The primary difference between protists and Eubacteria/Archea (bacteria) is that protists are more complex, having a nucleus. This bacteria is a single celled organism, but it has no nucleus. It is in the Kingdom Eubacteria.

Many protists appear to be both plant and animal. Like plants, they are green, and can create their own food. However, like animals, they have moving body parts, and are able to move around their environments.

How do you think this protist – named Euglena – moves around?

See the whip like tail on this drawing of the Euglena? The tail helps the single celled organism move around. The Euglena can make its own food so it is both plant and animal like.

Biologists believe that the ancient protists were the ancestors of plants and animals.