Environmental Science: Core Concepts for Level 3
Systems, Matter, and Energy
Environmental science treats the environment as a set of interacting systems: the atmosphere, hydrosphere, geosphere, and biosphere. Energy flows through these systems while matter cycles within them. The laws of thermodynamics are foundational: energy is conserved but degrades in quality, which is why food chains rarely exceed four or five trophic levels. Expect questions that ask you to trace energy loss (roughly 90% per transfer) versus nutrient recycling, where nothing is destroyed.
Biogeochemical Cycles and Ecosystems
Know the carbon, nitrogen, phosphorus, and water cycles, including the human alterations: fossil-fuel combustion, fertilizer application, and wetland drainage. Distinguish biotic (living) from abiotic (nonliving) factors and producers, consumers, decomposers. Concepts of carrying capacity, limiting factors, biodiversity, and succession appear frequently.
Human Impact and Management
Candidates should understand pollution pathways, air and water quality indicators, solid and hazardous waste, renewable versus nonrenewable resources, and sustainability principles. Recognize the difference between mitigation (reducing the source) and adaptation (adjusting to effects).
Traps to Watch
Common traps include confusing weather with climate, treating conservation as identical to preservation, and assuming recycling eliminates waste rather than diverting it. Another trap is conflating point-source and nonpoint-source pollution; agricultural runoff is the classic nonpoint example.
Worked Rule of Thumb
When a question asks about energy in a food chain, apply the 10% rule: if producers capture 10,000 units, primary consumers receive about 1,000, secondary consumers about 100, and tertiary consumers about 10. If a choice contradicts this magnitude of loss, it is likely wrong.