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 explores images of elephants with and without tusks, which serve as phenomena for learning about selection and human impacts on the frequency of traits within populations.

In this activity, students find a scientist with whom they can relate in some way and then explore and reflect upon the impact of that scientist’s work.

This activity explores an image of a moth with unusual markings on its wings, which serves as a phenomenon for learning about mimicry and adaptation.

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.

In this activity, students build a paper model of DNA and use their model to explore key structural features of the DNA double helix. This activity can be used to complement the short film The Double Helix.

This activity explores images of anole lizards subjected to strong winds, which serve as phenomena for learning about natural selection and the impacts of extreme climate events.

This activity guides the analysis of a published scientific figure from a study that investigated how anole lizards may adapt to extremely cold temperatures.

This activity guides the analysis of a published scientific figure from a study that investigated physiological and genetic adaptations in the Bajau, a group of people who traditionally do freediving.

This activity guides the analysis of a published scientific figure from a study that investigated genetic factors contributing to skin color differences, particularly within African populations.