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Productivity
AQA A-level biology productivity year 13
| Term | Definition |
|---|---|
| Trophic levels | Hierarchy in a food chain with each level containing organisms that share the same function in terms of predation & nutritional relationship to primary producers (e.g., primary, secondary, tertiary, & quaternary (in some aquatic environments) |
| Why not all energy from the sun is converted into chemical energy | Not all wavelengths are absorbed by photopigments since most are reflected back into space, light could fall on non-photosynthetic parts or just pass right through the plant, or something else might limit photosynthesis such as carbon dioxide levels |
| Why energy is lost at each trophic level | Animals lose energy through urine, faeces & respiration so for organisms higher up on the trophic level they absorb much less energy from the sun for each organism they eat. Also, not all of the organism will be edible |
| Productivity (with units) | The efficiency at which a biological system is able to convert energy not biomass. Generally measured in energy converted to biomass per area/volume per allotted length of time |
| Gross Primary Productivity (GPP) | Total quantity of chemical energy stored in plant biomass (either in KJ or g) in an area or volume per year |
| Net Primary Productivity (NPP) | Chemical energy stored in plant biomass left over after the energy needed for respiration (R) is removed, this is the energy available to other trophic levels |
| How to calculate Net Primary Productivity (NPP) | NPP = GPP - R Usually measured in KJm^-2yr^-1 although sometimes KJm^-3yr^-1 for some aquatic plants |
| How to calculate Net consumer productivity (N) | N = I - (F + R) I = ingested energy F = faeces R = respiration |
| Equation to calculate percentage efficiency of energy transfer between trophic levels | %efficiency = energy available after transfer/energy available before transfer x 100 |
| How farming practices increase energy transfer efficiency between trophic levels (4 ways) | Reduce energy lost from respiration by restricting movement, keeping them warm, optimum amount and type of food for growth with little waste, removing sources of predation & disease |
| How farming practices increase productivity in crops (3 ways) | Increasing fertilisers, removing competition (such as weeds & other plants), & reducing predation (from plant eating animals e.g., with pesticides) |
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Study_B
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