Sam wished to investigate how fertilizer run-off affects the growth of algae in

Question

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. Me placed 900 mL of water into each of five 1000 mL. glass beakers. To each beaker he added 5 mL of water from an aquarium that contained a large concentration of algae. The beakers were placed under a grow light that 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. i) What is the dependent variable in this experiment? a. Amount of fertilizer b. Amount of water c. Number of algae cells d. Hours of daylight ii) What is the independent variable in this experiment? a. Hours of daylight b. Number of algae cells c. Size of the beakers d. Amount of fertilizer iii) Which of the following is NOT a controlled variable in this experiment? a. Amount of light b. Amount of aquarium water c. Amount of fertilizer d. Size of the beakers

Explanation / Answer

i) Dependent Variables are those things on which Scientist or in our case Sam focuses his obsevations to see how these things responds to the changes made in the experiment.

Here Dependent Variable is c. Number of algae cells.

ii) Independent Variables are Those things Which is changed by the scientist, Which can be changed in a given experiment to Change the Experimental Results.

Here Independent Variables is d. Amount of fertilizer.

iii) Controlled Variable are those quantities which are kept constant throughout the experiment and it does not primarily effect the outcome.

Here NOT a controlled variable is b. Amount of aquarium water.

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