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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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- Fall '11