Ecology, Environment and Conservation
Ecosystems and energy
You must understand the terms habitat, population, community and ecosystem, and how organisms depend on each other. Food chains and webs show energy flow; energy is lost at each trophic level through respiration, movement and excretion, which is why pyramids of energy narrow upward. A trap is reversing arrows in food chains: arrows show the direction energy flows, from eaten to eater.
Cycles and interdependence
Know the carbon and water cycles and the roles of decomposers. Photosynthesis removes carbon dioxide; respiration and combustion release it. Predator-prey relationships and competition shape populations.
Human impact
Learn how pollution, deforestation, overfishing, habitat destruction and introduced species affect ecosystems. Conservation aims to protect biodiversity through reserves, laws, recycling and sustainable use of resources.
Sampling and data
Quadrats and transects estimate population size. Use random placement to avoid bias. A rule of thumb: estimated population = (total area ÷ quadrat area) × average number per quadrat.
Worked example
A student counts 8 daisies in a 0.5 m² quadrat and the field is 200 m². Population estimate = (200 ÷ 0.5) × 8 = 400 × 8 = 3200 daisies. State that this is an estimate, because the quadrat sample may not represent the whole field.