chlamydomonas-1

chlamydomonas-1 - In this anterior region are seen two...

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Chlamydomonas 1 Chlamydomonas Chlamydomonas is the name given to a genus of microscopic, unicellular green plants (algae) which live in fresh water. Typically their single-cell body is approximately spherical, about 0.02 mm across, with a cell wall surrounding the cytoplasm and a central nucleus. Two filaments of cytoplasm, flagella , (sing. flagellum ), extend from one end, and their whip- like lashings pull the chlamydomonas through the water and rotate it at the same time. A single, cup-shaped chloroplast occupies the greater part of the cell. In this chloroplast is a protein region called a pyrenoid , which is involved in starch production and may be surrounded by starch granules. A region of cytoplasm near the origin of the flagella is sensitive to light, and associated with this is a red pigment spot whose shadow, when cast on the sensitive area, is thought to cause turning movements of the chlamydomonas and so bring it into the region where the intensity of the light is most suitable for it.
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Unformatted text preview: In this anterior region are seen two spherical vacuoles which swell and collapse alternately. These contractile vacuoles are concerned with the expulsion of excess water absorbed by osmosis. Nutrition. Chlamydomonas makes its food in the same way as green plants, but without the elaborate system of roots, stem and leaves of the higher plants. It is surrounded by water containing dissolved carbon dioxide and salts so that in the light, with the aid of its chloroplast, it can build up starch by photosynthesis. From this carbohydrate, with additional elements, it can synthesize all the other materials necessary for its existence. Gaseous exchange . No special breathing organs are present; the oxygen needed for respiration diffuses in from the water through the entire surface of the cell. Similarly, carbon dioxide diffuses in during photosynthesis. Chlamydomonas flagellum contractile vacuoles pigment spot nucleus pyrenoid chloroplast cell wall cytoplasm © D.G. Mackean...
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