Matter and Energy in Ecosystems
- Biology
- Ages 11–14 · Grades 6–8
What you’ll find out
- Energy enters as sunlight, flows one way through trophic levels, and is lost as heat.
- Only about ten per cent of energy passes from one trophic level to the next.
- Matter such as carbon is recycled between living things and the environment and is conserved.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
Energy flows
Energy enters almost every ecosystem as sunlight, which producers capture through photosynthesis and store in food. When a herbivore eats a plant, only a small part of that energy reaches it, because the plant used much of its energy to live and grow, and much is lost as heat. On average, only about ten per cent of the energy at one feeding level passes to the next. This is why an energy pyramid is wide at the bottom, with many producers, and narrow at the top, with few top predators.
Matter cycles
Unlike energy, which flows through an ecosystem and is lost as heat, matter is recycled. Carbon is a good example. Plants take in carbon dioxide from the air and use its carbon to build sugars. Animals obtain that carbon by eating plants or other animals. Through respiration, both plants and animals return carbon dioxide to the air. When organisms die, decomposers break down their bodies and release the remaining carbon. The same atoms cycle endlessly between the living world and the environment.
Curriculum links: NGSS MS-LS2-3 · England KS3: Interactions and interdependencies · Cambridge Lower Secondary Stages 7–9: Biology · NCERT Science, Classes 6–8