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Algae

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Figure %: Eukaryotic and Prokaryotic flagella

Dinoflagellates

Dinoflagellates are mostly unicellular. The cell wall of these algae is only present when in the cyst stage. Most species of dinoflagellates have two flagella. One typical flagellum extends behind the cell. The other, usually shorter flagellum lies in a groove encircling the cell.

Dinoflagellates are an important component of plankton, the primary producers of organic material in the oceans. While this makes them important as a food source, some species of dinoflagellates are poisonous. The Red Tides common off the coasts of Florida and Mexico are caused by dinoflagellates and can kill millions of fish.

Red Algae

Red algae are mostly multicellular marine seaweeds. Like the green algae and higher plants, their chloroplasts have a two membrane envelope; red algae is often placed in the kingdom Plantae. In addition to chlorophyll a and b, red algae have accessory pigments called phycocyanins and allphycocyanins that contribute to the red coloration of some species. Their reproductive cycle involves alternation of generations like that of the brown algae, though no red algae have flagellated gametes, while some brown algae do.

Blue-green Algae (cyanobacteria)

For many years, cyanobacteria, a group of photoautotrophic eubacteria, were mistakenly classified as algae. They formed the group called blue-green algae. The lack of a defined nucleus and organelles such as chloroplasts make it clear that these are in fact eubacteria rather than algae. Cyanobacteria are discussed in the SparkNote on Monera.

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