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The Efficiency of Ecosystems

Edexcel A-level BiologyTopic 15 of 1620 lessons

Revision notes for The Efficiency of Ecosystems in Edexcel Biology B (9BI0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. Food ChainsA food chain shows how energy (and biomass) is transferred from one organism to the next as each is eaten.
  2. Food WebsIn real ecosystems most organisms eat more than one type of food and are eaten by more than one predator.
  3. Ecological PyramidsAn ecological pyramid shows a quantity at each trophic level of a food chain as a horizontal bar.
  4. Pyramid of NumbersA pyramid of numbers shows the number of individual organisms at each trophic level in a food chain, in a given area at one time.
  5. Pyramid of BiomassA pyramid of biomass shows the total mass of living organisms at each trophic level, per unit area (or volume, for aquatic habitats), at one moment…
  6. Inverted Pyramids of NumbersPyramids of numbers are not always pyramid-shaped.
  7. Energy Losses in ProducersEnergy enters an ecosystem when producers trap light energy in photosynthesis and convert it into chemical energy in organic molecules such as…
  8. Energy Losses between ConsumersWhen a consumer eats, only a small part of the energy in its food ends up in its own body tissues, where it is available to the next trophic level.
  9. Efficiency of Energy TransferTo compare how well energy passes along a food chain, we calculate the efficiency of energy transfer between trophic levels. efficiency (%) =…
  10. Gross Primary ProductivityGross primary productivity (GPP) is the rate at which producers convert light energy into chemical energy in organic molecules by photosynthesis.
  11. Net Primary ProductivityPlants use some of the energy they fix in photosynthesis for their own respiration, to power processes such as active transport and protein synthesis.
  12. The Limitations of Efficiency CalculationsEfficiency calculations depend on energy values for each trophic level, and these are very hard to measure accurately.
  13. Energy Transfer and Food Chain LengthBecause only a small fraction of energy passes from one trophic level to the next, food chains are short.
  14. Nutrient RecyclingEnergy flows through an ecosystem in one direction: it enters as light and leaves as heat, and it is never recycled.
  15. Conditions for Recycling NutrientsDecomposers are living organisms, so the rate at which they recycle nutrients depends on the conditions they need to grow and respire.
  16. Microorganisms in the Nitrogen CycleNitrogen is needed to make amino acids, proteins and nucleic acids.
  17. Microorganisms in the Carbon CycleCarbon is constantly recycled between the atmosphere, living organisms, soil and oceans.
  18. Short-term Carbon SinksA carbon store (reservoir) is anywhere carbon is held.
  19. Long-term Carbon SinksSome carbon is locked away for thousands to millions of years in long-term carbon sinks.
  20. Human InfluenceBefore the Industrial Revolution (around 1750), the concentration of CO2 in the atmosphere was about 280 ppm (parts per million).

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