Determine the variables tested in each of the following experiments. If applicable, determine and identify any positive or negative controls. Submit this exercise to your instructor upon completion. 1. A study is being done to test the effects of habitat space on the size of fish populations. Different sized aquariums are set up with six goldfish in each one. Over a period of six months, the fish are fed the same type and amount of food. The aquariums are equally maintained and cleaned throughout the experiment. The temperature of the water is kept constant. At the end of the experiment the number of surviving fish are surveyed.
A. Independent Variable: Different sized aquariums
B. Dependent Variable: number of fish that survived
C. Controls: Negative controls are the food, maintenance, water temperature.
2. To determine if the type of agar affects bacterial growth, a scientist cultures E. coli on four different types of agar. Five petri dishes are set up to collect results:
One with nutrient agar and E. coli
One with mannitol-salt agar and E. coli
One with MacConkey agar and E. coli
One with LB agar and E. coli
One with nutrient agar but NO E. coli
A. Independent Variable: Four different types of agar
B. Dependent Variable: Bacterial growth
C. Controls: Negative control is the petri dish with nutrient agar but no E. coli.