This animation shows how the proton gradient across the mitochondrial membrane powers the ATP synthase enzyme to make ATP. It is the third of three animations about cellular respiration.

This animation shows how the enzyme complexes of the electron transport chain harvest energy from cofactor molecules to pump protons across the mitochondrial membrane and establish a chemical gradient. It is the second of three animations about cellular respiration.

This animation shows the reactions of the citric acid cycle, which splits off carbon atoms and generates energy-rich reduced forms of cofactor molecules. It is the first of three animations about cellular respiration.

This activity allows students to formulate and analyze scientific questions.

This video follows biologist Shane Campbell-Staton, who is studying the adaptations that allow deer mice living at high elevations to stay warm and active during the winter.

This film explores the foundational research in the Serengeti National Park, Tanzania, that uncovered many of the ecological principles that govern how animal populations and communities are regulated.

This activity explores an image of tattoo ink particles inside cells, which serves as a phenomenon for learning about the structure and color of human skin.

This film explores the species-area relationship, a general ecological rule that describes how the number of species in a habitat changes with area, and shows how it has been applied to the conservation of protected areas.

This multipart animation series explores the process of photosynthesis and the structures that carry it out.

This activity explores images of wolves hunting a moose on Isle Royale, which serve as phenomena for learning about predator-prey population dynamics.

This activity guides the analysis of a published scientific figure from a study that investigated the effects of tourism on cougars and cottonwood trees in a national park.

This activity analyzes a published scientific figure from a study in Serengeti National Park, Tanzania. In this study, scientists investigated how the eradication of rinderpest disease led to a boom in the wildebeest population.