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This Click & Learn traces the flow of energy from the Sun all the way to cells within organisms. The embedded questions and calculations guide students’ understanding of how energy is distributed through a variety of ecosystems.

This animation shows two examples of how the cell uses energy from ATP. It is the sixth of six animations about cellular respiration. These animations bring to life the molecular engines inside mitochondria that generate ATP, the main source of chemically stored energy used throughout the body.

This animation shows how the pyruvate dehydrogenase enzyme complex converts pyruvate into acetyl-CoA. It is the second of six animations about cellular respiration.

This animation shows how glycolysis converts glucose into pyruvate through a series of enzyme reactions. It is the first of six animations about cellular respiration. These animations bring to life the molecular engines inside mitochondria that generate ATP, the main source of chemically stored energy used throughout the body.

This animation shows how the proton gradient across the mitochondrial membrane powers the ATP synthase enzyme to make ATP. It is the fifth of six animations about cellular respiration. These animations bring to life the molecular engines inside mitochondria that generate ATP, the main source of chemically stored energy used throughout the body.

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 fourth of six animations about cellular respiration. These animations bring to life the molecular engines inside mitochondria that generate ATP, the main source of chemically stored energy used throughout the body.

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 third of six animations about cellular respiration. These animations bring to life the molecular engines inside mitochondria that generate ATP, the main source of chemically stored energy used throughout the body.

This interactive module allows students and educators to build models that explain how the Earth system works. The Click & Learn can be used to show how Earth is affected by human activities and natural phenomena.

This interactive module allows students to collect and analyze data from a virtual river to construct biomass and energy pyramids.

This video describes how scientists silence different genes in regenerating planaria to study the process of regeneration at the molecular level.

This interactive module explores examples of how changes in one species can affect species at other trophic levels and ultimately the entire ecosystem.

This film tells the story of the ecologists who first documented the role of keystone species in ecosystem regulation.