Question

Read the following examples that use the above terms: A farmer wanted to test the effects of different amounts of fertilizer on tomatoes. He decided to measure the weight of the tomatoes from the plants (yield), since selling his tomatoes generates income. He applies different amounts of fertilizer (the independent variable) to different batches of his plants, and then determines the yield (the dependent variable) of the different batches to decide what amount of fertilizer works best. He includes some unfertilized plants for his control. The yield is dependent on the amount of fertilizer. The amount of fertilizer is independent because the farmer can decide how much he will use. Practice Part A: SCENARIO 1: A microbiologist working for a pharmaceutical company has isolated a chemical from a newly discovered strain of a fungus. He has done some preliminary tests and thinks that the chemical might kill the bacteria that cause gonorrhea. He prepares some bacterial growth medium (aka “agar”) and adds the new chemical to one batch, and leaves one without the antibiotic. He then adds the same amount of the bacteria that cause gonorrhea to each container of growth media and incubates them.

The microbiologist’s hypothesis was that if____________________________________, then ___________________________________________________________________. In this experiment, the antibiotic is the ________________________________________ Whether or not the bacteria can grow in the presence of the antibiotic is the ___________ ________________________________________________________________________ The growth media without the antibiotic is the __________________________________ Why was the same amount of bacteria added to both containers of growth media? _______________________________________________________________________ SCENARIO 2: Phyllis has just purchased a home in Florida. She is very excited about growing plumeria trees in her yard. She wants the trees to produce as many flowers as possible so she decides to test if different amounts of water to see if that has an effect on the number of flowers. Her sprinkler system automatically releases a set amount of water (gallons per minute) so the only way for her to adjust the water amount is to shorten/ lengthen the amount of time the plants get watered. Tree #1 gets watered every day for 2 hours. Tree #2 gets watered every other day for 2 hours. Tree #3 gets watered twice a day for 2 hours each interval. What is the independent variable of this experiment? ________________________________________________________________________ What is the dependent variable of this experiment? ________________________________________________________________________ What is a constant of this experiment? ________________________________________________________________________ What is another constant of this experiment? ________________________________________________________________________

Answer 1

Scenario 1:

The microbiologist's hypothesis is that if the chemical from a newly discovered Fungus kills the caustive bacteria of Gonorrhoea, then there should be no bacterial growth on the growth medium containing the antibiotic or Fungal extract.

In this experiment, the antibiotic is the independent variable and whether or not bacteria can grow in the presence of antibiotic is the dependent variable (on which the results of the hypothesis are based).

The growth medium without the antibiotic is the positive control (For which it is certain that the bacteria will grow and the results can be easily compared to that of the results from the bacterial culture containing antibiotic)

The same amount of bacteria was added to the both containers of growth media for maintaining uniformity in treatments so that the results could be accurately compared between the given treatments.

Scenario 2:

For this experiment, independent variable is different amounts of water

The dependent variable is The number of flowers

The constant of this experiment is the duration of watering the plants ( 2 hours)

The other constant is the set amount of water (Gallons/minute) (but not sure for this)