Question

Which of the following descriptions constitutes a controlled experiment?

a-growing one set of 10 seedlings under white light and one set of the same type of seedlings under red light and measuring their growth over a period of two weeks
b-using a microscope to observe organisms present in a sample of pond water and recording the number of each type of organism observed
c-growing one set of 10 seedlings under white light at 30°C and one set of a different type of seedlings under red light at 25°C and measuring their growth over a period of two weeks
d-setting up a bird feeder and compiling a list of all of the bird species seen at the feeder over a period of several weeks

Answer 1

A controlled experiment is best represented by the scenario where two sets of identical seedlings are grown under different light conditions to compare their growth over the same period.

Step-by-step explanation:

The description that constitutes a controlled experiment is option (a): growing one set of 10 seedlings under white light and one set of the same type of seedlings under red light and measuring their growth over two weeks. This option clearly outlines an experiment with an independent variable (the color of the light) and a control group (seedlings under white light), allowing for a direct comparison of plant growth under different light conditions while keeping other variables like seedling type and measurement period consistent.

In the given options, example A is a controlled experiment because it involves growing one set of seedlings under white light and another set under red light, with the only difference being the color of light. The growth of the seedlings is measured over two weeks to determine the effect of light color on their growth.