This AP® Biology content examines how species interactions, energy flow, and environmental change shape the structure and stability of ecological communities. Learners will explore how competition, predation, symbiosis, and resource availability influence species composition and community dynamics. They will also investigate how environmental pressures, invasive species, and human activities disrupt ecosystems, and how geological and meteorological events drive long-term ecological change. Learners will analyze key patterns in community and ecosystem energy dynamics and predict the effects of interspecific ecological interactions. Coming soon: new interactive content on NPP and energy flow between producers and consumers! AP® is a registered trademark of the College Board, which has not reviewed this resource.