BRAINCAKEEnergy and Ecosystems
Revision notes for Energy and Ecosystems in AQA Biology (7402). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Producers, Consumers and DecomposersEvery ecosystem depends on a flow of energy through organisms, which can be grouped by how they obtain their energy.
- Trophic LevelsA trophic level is the position an organism occupies in a food chain, based on how it gets its energy. • Trophic level 1: producers • Trophic level…
- BiomassBiomass is the total mass of living material in a given area (or volume, for aquatic ecosystems) at a particular time.
- Measuring Biomass - Dry MassDry mass is the mass of an organism's tissue after all the water has been removed.
- Calorimetry and Chemical Energy in BiomassThe chemical energy stored in dry biomass can be estimated using calorimetry.
- Gross Primary ProductionGross primary production (GPP) is the chemical energy store in plant biomass, in a given area or volume.
- Net Primary ProductionNet primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
- NPP = GPP - RThe relationship between gross and net primary production is: NPP = GPP − R where NPP is net primary production, GPP is gross primary production and…
- Net Production of ConsumersConsumers also lose much of the chemical energy they take in.
- Efficiency of Energy TransferOnly a small proportion of the energy at one trophic level is transferred to the biomass of the next.
- Calculating Percentage EfficiencyThe efficiency of energy transfer between two trophic levels is calculated as: percentage efficiency = (energy transferred to the higher level /…
- Farming Practices and ProductivityPrimary productivity and secondary productivity are the rates of primary and secondary production.
- Reducing Respiratory Losses in LivestockIn a human food chain, much of the energy that livestock take in is used in respiration and lost as heat, rather than being stored as meat, milk or…
- Simplifying Food Webs to Reduce Energy LossIn a natural ecosystem, energy from producers flows into many food chains.