Sam wished to investigate how fertilizer run-off affects the growth of algae in freshwater lakes and streams. He set his experiment up in this way. He placed 900 mL of water into each of the five 1000 mL glass beakers. To each beaker he added 5 ml of water from an aquarium which contained a large concentration of algae. The beakers were placed under a grow light which was timed to provide 12 hours of light each day. Liquid fertilizer was added to the beakers in the following amounts: Beaker A-8 ml fertilizer, Beaker B-6 ml fertilizer, Beaker C-4 ml fertilizer, Beaker D-2 ml fertilizer and Beaker E-no fertilizer. Each week a random sample from each of the beakers was examined under a microscope to get a count of the number of algae cells present. What is the independent variable in this experiment? The Independent Variable in Sam’s Experiment: Fertilizer Run-Off and Algae Growth

Sam’s Experiment’s Independent Variable: Fertilizer run-off and Algae growth

Sam created an experiment using five 1000mL glass beakers. Each contained 900mL water, 5mL water from an aquarium containing high levels of algae. The beakers were then diluted with different amounts of fertilizer: Beaker A-8 ml; Beaker B-6 ml; Beaker C-4 ml; Beaker F- 4 ml; Beaker H- 2 ml and Beaker W- 1 ml. To count the amount of algae cells, each week, each beaker was placed under a light source for twelve hours. Each beaker was then examined with a microscope. This experiment has an independent variable, which is the amount of fertilizer that was applied to each beaker. Sam will be manipulating this variable in order to study the impact of fertilizer runoff on the growth and development of alga. Sam is testing various amounts of fertilizer to see how they affect the growth of the algae in each beaker. Sam is able to determine the effect of fertilizer runoff on the growth of alga cells by comparing their numbers in the beakers. Cont….

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