Nature of ecosystems: structure, energy flows, trophic levels, food chains and food webs
An ecosystem is a community of living things interacting with their physical environment. Energy passes from plants to animals through a series of feeding levels called trophic levels.
Real World
In the Serengeti, the food web connecting grasses, wildebeest, zebras, and lions transfers energy across four trophic levels; only around 10% of energy passes between each level, which is why vast areas of grassland are needed to support just a small population of apex predators.
Exam Focus
When drawing or describing food webs, show direction of energy flow with arrows and state the approximate 10% energy transfer efficiency.
Essay Framework
Use PEEL to structure every paragraph. Tap each step for guidance and an example.
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