When DNA research first began, it required almost an entire day to extract the molecules from a cell nucleus. Now it requires less than an hour. Scholars learn about the early theories of DNA with an online interactive, videos,...

[Free Registration/Login may be required to access all resource tools.] A cell is the smallest structural and functional unit of an organism. Learn more about cell biology in this learning module produced by CK-12.

[Free Registration/Login may be required to access all resource tools.] Read grade-level texts, complete activities, and take assessments about cell biology.

[Free Registration/Login may be required to access all resource tools.] How Wegener's hypothesis of continental drift was refined.