VCE Environmental Science cheat sheet

Trophic levels: producers (T1), primary consumers (T2), secondary consumers (T3), tertiary consumers (T4); decomposers act at every level and are not a trophic level.

Energy transfer between trophic levels is typically 10% (range ~5–20%); energy is lost as heat via respiration, in egestion/excretion, and in uneaten biomass.

Net primary productivity = gross primary productivity − respiration by producers (NPP = GPP − R); units are typically kJ m⁻² yr⁻¹ or g m⁻² yr⁻¹.

Pyramids of numbers, biomass and energy differ: numbers pyramids can invert (one tree, many insects); energy pyramids never invert.

Carbon cycle fluxes: photosynthesis (atmosphere→biomass), respiration and decomposition (biomass→atmosphere), combustion of fossil fuels and biomass (→atmosphere), ocean uptake/dissolution.

Nitrogen cycle steps in order: nitrogen fixation (N₂→NH₃/NH₄⁺), nitrification (NH₄⁺→NO₂⁻→NO₃⁻), assimilation, ammonification, denitrification (NO₃⁻→N₂).

Phosphorus has no significant gaseous phase; it cycles via weathering of rock, uptake, decomposition and sedimentation/runoff, so it is often limiting in soils.

Ecological succession: primary succession begins on substrate with no soil (bare rock, lava); secondary succession begins after disturbance where soil and seed bank remain.

Population growth: exponential when resources unlimited (dN/dt = rN); logistic when density-dependent limits apply, approaching carrying capacity K.

Earth's four spheres: atmosphere (gases), biosphere (living things), hydrosphere (water), lithosphere/geosphere (rock and soil); matter and energy move between them.

Greenhouse gases absorb and re-emit longwave infrared radiation: CO₂, CH₄, N₂O, water vapour, tropospheric O₃ and CFCs; N₂ and O₂ are not greenhouse gases.

Global warming potential over 100 years: CH₄ ≈ 28–30 × CO₂; N₂O ≈ 265–298 × CO₂; CFCs are thousands of times CO₂.

Ozone depletion is driven by chlorine and bromine radicals from CFCs/halons in the stratosphere; ozone loss is distinct from the greenhouse effect.

Acid deposition: SO₂ and NOₓ oxidise to H₂SO₄ and HNO₃; pH below ~5.6 is considered acid rain; impacts include soil cation loss and lake acidification.

Eutrophication sequence: nutrient enrichment (N, P) → algal bloom → shading and die-off → bacterial decomposition → oxygen depletion → fish kills.

Bioaccumulation is uptake of a substance by an organism; biomagnification is increasing concentration up the food chain, greatest for fat-soluble, persistent compounds (e.g. DDT, PCBs, methylmercury).

Air quality indicators include PM₁₀, PM₂.₅, CO, NO₂, SO₂, O₃ and Pb; PM₂.₅ is more hazardous than PM₁₀ because it penetrates deep into alveoli.

Indicator species and monitoring: lichens indicate SO₂ levels; macroinvertebrate indices (e.g. SIGNAL-type scoring) grade water quality; turbidity, DO, pH, EC and nutrients are standard water tests.

Biodiversity has three levels: genetic, species and ecosystem diversity; each is assessed separately and can respond differently to the same pressure.

Species richness = number of species present; evenness describes relative abundance; indices such as Shannon–Wiener combine both richness and evenness.

Natural change agents: fire, drought, flood, cyclones, disease, volcanic activity, succession and climate cycles; human-induced change is often faster and more extensive.

Fire regimes matter: frequency, intensity, season and patchiness determine whether fire promotes regeneration (e.g. serotiny, resprouting) or degrades ecosystems.

Threats to biodiversity ranked by impact include habitat loss and fragmentation, invasive species, overexploitation, pollution, and climate change.

Habitat fragmentation creates edge effects, reduces patch area, and isolates populations, lowering gene flow and increasing extinction risk in small populations.

Conservation categories (IUCN): Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern, Data Deficient.

In-situ conservation protects species in their habitat (reserves, corridors, fire management); ex-situ conservation is off-site (seed banks, captive breeding, botanic gardens).

Restoration success is judged against reference ecosystems using indicators: species composition, structural complexity, soil condition, and ecological function.

Sustainability requires meeting present needs without compromising future generations; assessed across environmental, social and economic dimensions.

Ecological footprint = area of land and water needed to supply resources and absorb wastes, expressed in global hectares (gha); compared with biocapacity.

Carrying capacity can be exceeded temporarily by drawing down natural capital (overshoot); Earth Overshoot Day marks the date of annual overshoot.

Renewable energy sources: solar, wind, hydro, geothermal, tidal, wave, biomass; non-renewable: coal, oil, gas, nuclear fuels (uranium).

Energy transformations in a coal plant: chemical → thermal → kinetic (steam) → electrical; overall efficiency typically 30–40%, with the rest lost as waste heat.

Life cycle assessment stages: goal and scope, inventory (inputs/outputs), impact assessment, and interpretation; it compares impacts per functional unit.

Climate projections use representative concentration pathways (RCPs) or shared socioeconomic pathways (SSPs); higher radiative forcing gives greater warming and sea-level rise.

Adaptation reduces vulnerability to impacts (sea walls, drought-resistant crops, early-warning systems); mitigation reduces causes (emissions cuts, carbon sinks, efficiency).

Environmental management tools: EIA, environmental management systems (ISO 14001), carbon pricing, tradable permits, regulation, and community-based management.