algaeăl´jē [key] [plural of Lat. alga=seaweed], a large and diverse group of primarily aquatic plantlike organisms. These organisms were previously classified as a primitive subkingdom of the plant kingdom, the thallophytes (plants that lack true roots, stems, leaves, and flowers). More recently, most algae have been classified in the kingdom Protista or in another major group called the eukarya (or eukaryotes), which includes animals and higher plants. The algae have chlorophyll and can manufacture their own food through the process of photosynthesis. They are distributed worldwide in the sea, in freshwater, and in moist situations on land. Nearly all seaweeds are marine algae. Algae that thrive in polluted water, some of which are toxic, can overmultiply, resulting in an algal bloom and seriously unbalancing their ecosystem.
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