Topic 5: Energy and ecosystems Flashcards
What is biomass?
Total dry mass of tissue or mass of carbon measured over a given time in a specific area
How can chemical energy store in dry biomass be estimated?
- Using calorimetry
- Energy released= specific heat capacity of water X volume of water X temp increase of water
Why is bomb calorimetry preferable to simple calorimetry?
reduces heat loss to surroundings
How could a student ensure that all water had been removed from a sample before weighing?
Heat the sample and reweigh it until the mass reading is constant
Define gross primary production (GPP)
Total chemical energy in plant biomass within a given volume or area
Define net primary productivity (NPP)
Total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses
Give the mathematical relationship between GPP and NPP
NPP= GPP-R
Why is most of the suns energy not converted to organic matter?
- most solar energy is absorbed by atmosphere or reflected by clouds
- photosynthetic pigments cannot absorb some wavelengths of light
- not all light falls directly on a chlorophyll molecule
- energy lost as heat during respiration/photosynthesis
How can the net production of consumers be calculated?
N=I-(F+R)
I: chemical energy from ingested food
F: energy lost as faeces and urine
R: respiratory losses
Why does biomass decrease along a food chain?
- energy lost in nitrogenous waste and faeces
- some of the organism is not consumed
- energy lost to surroundings as heat
Outline some common farming practices used to increase efficiency of energy transfer
- exclusion of predators: no energy lost to other organisms
- artificial heating: reduce energy lost to maintain constant body temperature
-restriction of movement - feeding controlled at the optimum
General equation for % efficiency
energy converted to a useful form (J) / total energy supplied (J) X 100
Explain why the length of food chains is limited
- energy lost at each trophic level
- insufficient energy to support a higher trophic level
