Ecosystems, Biodiversity and Environmental Science
Ecosystems, Biodiversity and Environmental Science tests food webs, energy flow, nutrient cycles, population interactions, biodiversity, and human impacts. Exam items often ask what happens when one population changes or why food chains are short.
Core concepts
- Producers make food by photosynthesis; consumers eat; decomposers break down dead matter and recycle nutrients.
- Arrows in food webs show energy flow from the eaten organism to the eater.
- Energy decreases at each trophic level; only about 10 percent transfers, so food chains are usually short.
- Matter cycles through carbon, water, and nitrogen pathways; energy flows one way through ecosystems.
- Biodiversity includes species richness, genetic variation, and ecosystem variety. It increases resilience to disturbance.
- Invasive species, habitat loss, pollution, and climate change reduce biodiversity.
Worked example
A grassland has 10,000 units of energy in grasses. Insects receive about 1,000; frogs about 100; snakes about 10. If snakes are removed, frogs may increase at first, then disease or food shortage may limit them. The reasoning is that energy limits population size, and removing a predator affects multiple levels, not just one.
Traps that cost marks
Reversing arrows; saying energy cycles; treating all bacteria as decomposers; equating biodiversity with number of individuals; assuming removing a predator only affects its prey.