Plant-Like Protists

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Plant-Like Protists

Imagine, if you will, an amoeba or other single-celled organism swimming along happily. It was enjoying a diet of bacteria when it engulfs a blue-green algae. The amoeba didn't digest it right away, and so the algae lived on. The algae continued to produce energy for the amoeba, and in turn, the amoeba kept it from being eaten by other critters. They both were doing rather well. The algae started to reproduce, which was great for the amoeba because it meant more food. Eventually, the amoeba reproduced and each daughter cell received some blue-green algae inside it.

Did this story happen? Quite plausable. Here we see the group known as plant-like protists, or more commonly, algae. Seaweeds are algae. So are most of the gross pond slimes and scum. Let's get to know the algaes.

Algae may be single celled, or it may be colonial, filamentous or very large, like kelp. Grab your microscopes, we're going in for a closer look at the one-celled variety.

When you look this closely at algae, you notice that they don't resemble plants too closely. These little critters are euglena. They resemble the animal like protists. They have the ability to move, they have the same shape, and they even have flagella, or whip-like tails. They're plant-like though. They produce their own food. The chlorophyll inside of them allows them to harness solar energy.

Many one-celled algae not only get their food from the sun, but can also engulf bacteria to eat it. Weird, huh? They have both plant and animal-like characteristics.

There are many algaes of importance. Diatoms are very interesting. These are plant-like, but they have shells, and the shells are microscopic beauties. These are part of the group known as plankton. Plankton is a general term for very small or microscopic organisms floating about in the water. Many marine animals are dependent on the plankton. Even many whales, the largest mammals, are dependent on these tiniest of organisms.

Many of the algaes are grouped by their color. Here is a table of information which you may find useful:

Golden Algae	Usually one-celled	These protists keep food reserves in an unusual way - they store them as drops of oil. This group is mostly flagellates and only rarely reproduce sexually.
Green Algae	filamentous, one celled or colonial	Though this group is most commonly in the water, it can be found on snow, treetrunks, and in the soil. This group is most similar to land plants.
Red Algae	One-celled or may be more complex. Leaf-like.	This algae is responsible for poisonous algal blooms which kill off animals in the water. Most interesting are this protist's economic uses. Most likely you've eaten red algae without ever knowing it.
Brown Algae	Usually multi-cellular, can be gigantic	This is the group most commonly thought of when the term "seaweed" is used. Giant kelp forests of Sargassum brown algae exist. These have similar structures to land plants. There are stalks and leaves, but also they have air bladders to keep the algae aimed at the sun.

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