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- There are about 10,000 species of diatoms; these organisms make up a major portion of ocean plankton and are also a major source of food for many small marine animals. Unlike other members of the division, diatoms sometimes reproduce sexually via a process called syngamy. Diatoms are encased in double shells which are made of silicon and fit together like two halves of a pillbox; some of these microscopic boxes are quite beautiful. These organisms are sometimes able to move around on their own by secreting cilia-like fibrils along a special groove called the raphe.
Diatom shells are used as abrasives in silver polish and toothpaste, as filters, and in highway reflectors.
- This biological division contains the diatoms, golden-brown algae, and yellow-green algae. Scientists estimate that there are about 12,000 species in this division. These organisms are all single-celled and are mainly found in marine environments. They conduct photosynthesis and contain chlorophylls a and c; diatoms and golden-brown algae also contain the acessory pigment fucoxanthin. They store their food as large droplets of oil or in the form of the carbohydrate leucosin. These organisms usually reproduce by cell division.
There are about 10,000 living species of diatoms, 1500 species of golden-brown algae, and 600 species of yellow-green algae.
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Biology Dictionary