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Euglena protozoan. Light micrograph of Euglena sp., a protozoan. This single-celled organism has a tail-like flagellum for locomotion (bottom left). The cytoplasm is green due to the large number of photosynthetic chloroplasts that form starch using sunlight. This food is stored in paramylum granules (large green ovals). The nucleus (green circle, centre right) contains genetic material. Euglena sp. lives in ponds and puddles, creating starch in sunlight and feeding off large organic molecules in the dark. Magnification: x400 at 35mm size. (KEYSTONE/SCIENCE PHOTO LIBRARY/ALEX RAKOSY, CUSTOM MEDICAL STOCK PHOTO/ SCIENCE PHOTO LIBRARY)