This video segment adapted from NOVA chronicles the discoveries that led to a radical new theory in which living organisms, not just geological processes, play an active role in cave formation. [5:42]

This module focuses on cell structure and how the organelles function together to form the smallest unit of life. The cell theory is also discussed along with the basics features of the cell. Site also includes an interactive practice...

Learn about the experiments by Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase that led to the discovery of DNA as the genetic material.

Learn about Thomas Hunt Morgan's experiments with the fruit fly (Drosophila melanogaster) as a model system.