Does the wavelength of light affect a plant’s growth?
Does the size of a fish tank determine how large a fish will grow?
Do wounds heal faster when they are covered by band-aids?
Students design the experiment, and must also identify the a control group and the independent and dependent variables in their experiment. There is also an advanced version of this activity for AP Biology that has more rigorous questions, and asks students to establish a null hypothesis.
Students do not actually conduct their experiments, due to equipment and time constraints. Optionally, the teacher may choose one to conduct as a class demonstration, like the question about whether aspirin will keep cut flowers fresh.