Environmental and Earth Science Contexts
This domain applies the same skills - measurement, data interpretation, experimental reasoning - inside Earth and environmental contexts. Expect graphs of atmospheric carbon dioxide, population counts, water-quality tables, trophic pyramids and questions about resources and human impact, often set in a Quebec or St. Lawrence River context.
Earth as interacting systems
The lithosphere, hydrosphere, atmosphere and biosphere exchange matter and energy. A change in one propagates: deforestation in a watershed increases runoff and erosion, which raises sediment loads in rivers and can bury spawning habitat.
Cycles and flows
- Water cycle - evaporation, transpiration, condensation, precipitation, infiltration, runoff.
- Carbon cycle - photosynthesis removes carbon dioxide; respiration, decomposition and combustion release it; oceans and soils are reservoirs.
- Matter cycles through ecosystems; energy flows one way, entering as sunlight and leaving as heat.
Energy in ecosystems
At each trophic level only about 10 % of the energy is transferred; the rest is lost as heat from respiration and in uneaten parts. This explains why food chains rarely exceed four or five levels, and why eating lower on the chain feeds more people per hectare.
Resources and impact
Renewable resources (solar, wind, hydro, biomass) are replenished on human timescales; non-renewable ones (fossil fuels, minerals) are not. Renewable does not mean harmless: hydroelectric reservoirs flood land and alter flow regimes, and wind turbines affect birds and bats.
Worked example
Producers in a grassland fix 10 000 kJ m⁻² yr⁻¹. With 10 % transfer, primary consumers receive 1 000 kJ, secondary consumers 100 kJ and tertiary consumers 10 kJ. If people eat the tertiary consumer, only 10 kJ m⁻² yr⁻¹ supports them; eating the primary consumer would supply 1 000 kJ. The reasoning that earns marks is the loss at each step through respiration, not the arithmetic alone.
Traps
- Saying energy is recycled. Matter cycles; energy flows and degrades.
- Confusing weather, which changes over days, with climate, which is measured over decades.
- Reading ppm as a percentage: 400 ppm is 0.04 %.
- Treating "natural" as automatically safe or "renewable" as zero impact.
- Miscounting trophic levels by starting at 1 for consumers instead of producers.