ABSTRACT
A central aim of science—perhaps the central aim—is to produce knowledge about the world, which involves formulating natural explanations of natural phenomena. Many scientists perform experiments in order to test new hypotheses and to extend existing knowledge. In experiments, there are three categories of variables: independent, dependent, and extraneous. Gregor Mendel's selective fertilization of pea plants illustrates a key feature of experiments. The patterns in characteristics resulting from his selective breeding of pea plants led Mendel to posit units of heredity that determine variation in inherited characteristics according to set patterns across biological organisms from pea plants to humans. Experiments involve introducing specific changes to a system in order to make observations about how the system responds. Experiments have different aspects—physical, technological, and social—that need to fit together in the right way for scientists to harvest useful evidence; how these aspects are arranged is the experimental setup.
