Plant-like Protists
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Printed: March 13, 2013
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C ONCEPT
Concept 1. Plant-like Protists
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Plant-like Protists
• Describe the plant-like protists.
What is pond scum?
Polluted water can form a frothy green scum on the surface. This "pond scum" is actually a living organism, algae.
The algae are plant-like protists. Usually the algae are too small to notice, but sometimes algae grow in excess
because of the excess nutrients in polluted water.
Plant-like Protists
Plant-like protists are known as algae (Figure 1.1). They are a large and diverse group. Plant-like protists are
autotrophs. This means that they produce their own food. They perform photosynthesis to produce sugar by using
carbon dioxide and water, and the energy from sunlight, just like plants. Unlike plants, however, plant-like protists
do not have true stems, roots, or leaves.
Most plant-like protists live in oceans, ponds, or lakes. Protists can be unicellular (single-celled) or multicellular
(many-celled). Seaweed and kelp are examples of multicellular, plant-like protists. Kelp can be as large as trees and
form a "forest" in the ocean (Figure 1.2).
Plant-like protists are essential to the ecosystem. They are the base of the marine food chain, and they produce
oxygen through photosynthesis for animals to breathe. They are classified into a number of basic groups (Table
1.1).
TABLE 1.1: Plantlike Protists
Phylum
Chlorophyta
Rhodophyta
Description
green algae - related to
higher plants
red algae
Number (approximate)
7,500
5,000
Example
Chlamydomnas,
Volvox
Porphyra
Ulva,
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TABLE 1.1: (continued)
Phylum
Phaeophyta
Chrysophyta
Pyrrophyta
Euglenophyta
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Description
brown algae
diatoms, golden-brown algae, yellow-green algae
dinoflagellates
euglenoids
Number (approximate)
1,500
12,000
Example
Macrocystis
Cyclotella
4,000
1,000
Gonyaulax
Euglena
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Concept 1. Plant-like Protists
FIGURE 1.1
Red algae are a very large group of
protists making up about 5,000–6,000
species. They are mostly multicellular and
live in the ocean. Many red algae are
seaweeds and help create coral reefs.
FIGURE 1.2
Macrocystis pyrifera (giant kelp) is a type
of multicellular, plant-like protist.
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Vocabulary
• algae (singular, alga): Plant-like protists, such as diatoms and seaweeds.
• autotroph: Organism that makes its own food.
• kelp: Plant-like, multicellular protist that can grow an "ocean forest."
Summary
• Plant-like protists are autotrophs, meaning they make their own food.
• Plant-like protists include algae, kelp, and seaweed.
Practice
Use the resource below to answer the questions that follow.
• Plant Protists at http://www.youtube.com/watch?v=o5ESHXKGBvA (4:03)
MEDIA
Click image to the left for more content.
1. How much of the total photosynthesis on the globe is carried out by phytoplankton? What does this mean for
aquatic ecosystems?
2. How are the flagella of dinoflagellates arranged?
3. What organisms have dinoflagellates as symbiotes? Why are dinoflagellates important to these organisms?
4. How do bivalves respond to red tides? What does this mean for humans?
• Red Tides at NOAA: http://oceanservice.noaa.gov/facts/redtide.html.
1.
2.
3.
4.
What is a red tide?
How are algae helpful?
How can some algae be harmful?
Are all algal blooms harmful? Explain your answer as fully as you can.
Review
1. How are some protists similar to plants?
2. What are some examples of plant-like protists?
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