Unicellular Organisms: Definition & Examples

Unicellular Organisms: Definition & Examples
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Lesson Transcript
Instructor: Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

Life takes a great variety of forms. This world is home to many simple organisms that live in a variety of environments. In this lesson, we will examine unicellular organisms to gain a better understanding of them.

Unicellular Organisms Defined

Unicellular organisms are composed of a single cell, unlike multicellular organisms that are made of many cells. This means that they each live and carry out all of their life processes as one single cell. Most unicellular organisms are microscopic; however, some are visible to the naked eye.

Examples of Unicellular Organisms

All prokaryotes, most protists, and some fungi are unicellular. Some of these organisms do live in large colonies, but each individual cell is a simple living organism. Let's look at some examples of unicellular organisms.

Valonia ventricosa is a protist. It is a unicellular algae and is one of the largest unicellular organisms that exists. They can be found in the Caribbean and as far north as Florida. They are usually solitary, but can sometimes be found in small groups. They have a spherical shape and are green in color. Like typical unicellular organisms, they eat, grow, reproduce, and die as one single cell.

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