Ans. Desmids belong to the Desmidiaceae family. The Desmids are single-cell green algae, which can found only in freshwater. The mixed desmids have spectacular symmetrical shapes. It is usually recognized by their symmetry. The two symmetric semi-cells are joined together by the narrow connections called the isthmus. The desmid algae play an important role in the complex food web of life. As with other plants, the desmid contains chlorophyll. This will helps the desmids to capture sunlight for the generation of photosynthesis. During this process, the algae absorb dissolved carbon dioxide from the water and manufacture their own food like sugar and starch.