Question

Stella wants to test the hypothesis “If carbon dioxide levels increase, the growth rate of sunflowers will increase.” She places five young sunflower plants into similar containers and sets up pumps that release different amounts of carbon dioxide into each container. She plans to measure the daily height of the plants for two weeks and graph the data. Which additional considerations would produce the most reliable experimental results?
A. She should also provide mist to each of the plants to keep the air moist and fertilize the plants. She should record her data in a bar graph for easy analysis.

B. She should increase her sample size to 50 plants and place them all in the same area. The plants receiving less CO2 should be given a little more water.

C. She should be sure to give all the flowers the same amount of water. She should make observations twice a day for four weeks for better results.

D. She should place one flower in a similar container, but not pump carbon dioxide into it. She should also give each plant the same amount of water.

Answer 1

The correct answer is option D. She should place one flower in a similar container, but not pump carbon dioxide into it. She should also give each plant the same amount of water.

In the experiment, a control should be present to compare the effect of the variable in the experiment. In the control sample, all the parameters except the variable should be same as the experimental group. In this way, the comparison of the effect of variable can be easily done in an experiment.

In this case, the variable is amount of carbon dioxide the plant receives. So, Stella should include a control group by placing the plant in the same container and leave it on atmospheric carbon dioxide supply, no extra carbon dioxide should be pumped into it.  Also, the amount of water she give to each plant should be the same to maintain the water level as constant.

Answer 2

Answer:

The correct answer would be D. She should place one flower in a similar container, but not pump carbon dioxide into it. She should also give each plant the same amount of water.

This flower would act as a control for her experiment. Thus, it would help her to compare the growth of plants when no carbon dioxide is pumped to the plant. Thus, it would help her find if the presence or absence of carbon dioxide would really affect the growth of a plant or not.

Secondly, all the variables other than the amount of carbon dioxide pumped must be kept the same. For example, each plant must get an equal amount of water, sunlight, space or container, nutrition et cetera.

it would help in maintaining the accuracy and reliability of the experiment.