After you set up a fish tank, you are sure to see algae growing in it. There is plenty of light, fertilizer in the form of fish droppings, and plants or glass for algae to cling to. You may see green strings of algae in the water or green spots growing on the glass. Your whole aquarium can turn green if you don’t stop the algae. To prevent the problem, you can add algae-eating fish or microorganisms to the water. Covering the aquarium for a few days will also kill algae, which need photosynthesis to survive. Multi-celled algae grow into larger organisms through cell division. For one-celled algae, the purpose of cell division is

Juan and carol were studying invertebrates in biology. they knew that segmented or earth worms preferred a dark, moist habitat. during this lab, they would be investigating the responses of organisms called planaria or dugesia tigrina. these were simple flatworms that still had a one-way digestive system and a very simple nervous system. juan and carol placed the planaria in a petri dish containing cool, distilled water that was partially covered with black paper. they shined a light on the dish. next, they removed the paper and placed a small amount of chicken liver at one end of the dish. they added a few large salt crystals to the water. finally, they added drops of hot water to the cool water in the petri dish. their results can be seen in the data table. according to their experiment, all but one conclusion is valid.