Topic 1 examines how energy flows linearly and matter recycles continuously through Earth's biological communities. Students explore the interconnected roles of producers, consumers, and decomposers within food webs, applying the 10% rule and trophic pyramids to quantify energy transfer and biomass carrying capacities. The unit details fundamental biogeochemical pathways, including the carbon, nitrogen, phosphorus, and hydrologic cycles, to track how matter moves between biotic organisms and abiotic reservoirs. Additionally, students evaluate ecosystem resilience by analyzing real-world ecological dynamics, such as trophic cascades, keystone species removal, agricultural eutrophication, and the biomagnification of persistent toxins. 

Topic 3 investigates the chemical, physical, and biological pollutants resulting from human activity and their impacts on public health and natural ecosystems. Students categorize air pollution dynamics by differentiating primary pollutants from secondary compounds formed via photochemical smog and thermal inversions. Water quality analysis focuses on distinguishing single point-source industrial discharges from diffuse non-point source agricultural runoff, alongside modeling the biological steps of nutrient-driven eutrophication. This topic also covers environmental toxicology and waste streams, evaluating how hazardous waste and microplastics bioaccumulate within organisms, biomagnify across trophic levels, and require science-based remediation strategies.