Final answer:
A control in scientific experiments is a part of the experiment that does not change and is used as a baseline for comparison. It helps eliminate the need for large sample sizes, statistical tests, and reduces the number of measurements needed. In an experiment testing the growth of algae, the control would be the ponds treated with an inert substance instead of phosphate.
Step-by-step explanation:
In the context of scientific experiments, a control is a part of the experiment that does not change, serving as a baseline for comparison. It is used to ensure that any observed effects are due to the variable being tested and not to other factors. Controls help eliminate the need for large sample sizes, statistical tests, and reduce the number of measurements needed. For example, in an experiment testing the growth of algae in freshwater ponds, the control would be the ponds treated with an inert substance instead of phosphate. By comparing the growth of algae in the treated ponds versus the control ponds, researchers can determine if phosphate limits algal growth.