Algae Diversity

Contributor: Felicia Sabur. Lesson ID: 12013

Algae may be gross when it's in your pool or fish tank, but it's actually very helpful! It's also not so simple with names like dinoflagellata and bacillariophyta! Discover diatoms and analyze algae!


Life Science

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

Lesson Plan - Get It!

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  • What organisms are the major producers of oxygen and nutrients in the aquatic ecosystems on the earth?

In this lesson, you will be learning about the three algae phyla of euglenoids, diatoms, and dinoflagellates.

If you missed or need to review the previous Related Lessons in our Kingdom Protista series, find them in the right-hand sidebar.

All of the algae that belong to these phyla are unicellular and make up a large part of the phytoplankton. Phytoplankton are microscopic marine plants that are so abundant that they are one of the major producers of oxygen and nutrients in the aquatic ecosystems on the earth.

Phylum Euglenophyta

structure of euglenophyta

The Phylum Euglenophyta is made up of hundreds of species of euglenoids. They are aquatic, unicellular protist that have both plant and animal characteristics. However, they don’t have a cell wall made of cellulose like plants.

Euglenoids are plant-like because they have chlorophyll and photosynthesize. They are also animal-like, because they can ingest food like protozoans.

Phylum Bacillariophyta

Diatoms are members of the Bacillariophyta Phylum and have shells made of silica. You can find them in fresh-water and salt-water ecosystems. They are a large part of the phytoplankton.

Diatoms reproduce by sexual and asexual reproduction. They will reproduce asexually for a few generations before reproducing sexually. Their reproduction cycle is a type of alterations of generations.

View the following video, Diatom Life Cycle from Dutton Institute, to get a better understanding of how it differs slightly from the alterations of generations you saw in the last Related Lesson on algae (right-hand sidebar).

As you watch the video, draw the diagram of the diatom lifecycle as the speaker describes it. Feel free to use the pause button as you draw the diagram.

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  • What are the differences and similarities between the diatoms lifecycle and the alternations of generations diagram you drew in the last lesson?

Phylum Dinoflagellata

Dinoflagellates have thick cell walls that are made of cellulose plates. They are unicellular and spin slowly as they move because they have two flagella located in grooves at right angles form each other. That is why they are sometimes called the spinning algae.

Dinoflagellates are found mostly in salt water, but a few can be found in fresh water. They are also a major part of phytoplankton, like diatoms. Watch this video from Iainp1211 to see Diatoms in action and up close:

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Several species of dinoflagellates are toxic. During the summer, it is possible for these creatures to over-populate, and the ocean takes on a reddish color. This known as a red tide and can make you sick of you swim in the waters or eat shellfish from those areas with a current red tide.

In the Got It? section, you will dig deeper into the event known as a red tide.

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