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Summary 13 Energy and ecosystems
- Institution
- AQA
Concise energy and ecosystems summary notes for the new linear A-level biology 7401/7402
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Energy and EcosystemsFood chains
Producers: photosynthetic organisms that use light energy, H2O, CO2 and mineral ions to get
organic substances.
Consumers: get energy from feeding on other organisms.
- Primary consumers eat producers
- Secondary consumers eat primary consumers
- Tertiary consumers eat secondary consumers
Decomposers: when a producer or consumer dies, decomposers break them down using
their energy to convert complex substances into simple components – these minerals and
elements are then released into the soil.
Biomass: total mass of living material in a specific area at a given time.
Gross production
Total quantity of energy that plants convert to organic matter
® Gross Primary Production (GPP) = the total amount of energy captured
® Net Primary Production (NPP) = the amount of energy stored by the producers and
potentially available to consumers and decomposers
® 20-50% of energy captured is lost during respiration, therefore:
NPP = GPP - Respiration
How is energy lost?
Not all of organism is eating or fully digested
Excretion
Heat loss
Respiration
Maintain body temperature
The Nitrogen Cycle
Importance of nitrogen:
- Proteins, amino acids etc.
- Few organisms can use pure nitrogen from the air
- Those who can will use nitrogen gas to make ammonium ions, then proteins
- Other life forms rely on these organisms
Nitrate levels are restored through recycling of nitrogen-containing compounds, but can be
increased using fertilisers and through decomposition.
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