Energy and Ecosystems Flashcards
Topic 5.3
Estimate chemical energy in dry biomass
Using calorimetry
Energy released = specific heat capacity of water x volume of water (cm cubed) x temperature increase of water
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
Equation containing GPP and NPP
NPP = GPP - R
where R represents respiratory losses
Equation for net production of consumers
N = I (F + R)
I: chemical energy from ingested food
F: energy lost as waste
R: respiratory losses
What is biomass?
Total dry mass of tissue or mass of carbon measured over given time in specific area
Why is most of Sun’s 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 chlorophyll molecule
- Energy lost as heat during respiration/ photosynthesis
Why does biomass decrease along food chain?
- Energy lost in nitrogenous waste (urine) & faeces
- Some of organism is not consumed
- Energy lost to surroundings as heat
Define Primary & Secondary productivity
- Rate of primary or secondary production
- Biomass in specific area over given time period (e.g. kJ ha-1 year -1)
Outline common farming practices used to increase efficiency of energy transfer
- Exclusion of predators: no energy lost to other organisms in food web
- Artificial heating: reduce energy lost to maintain constant body temp.
- Restriction of movement
- Feeding is controlled at optimum
Give general equation for % efficiency
energy converted to useful form (J) x 100/ total energy supplied (J)
Explain why length of food chains is limited
Energy is lost at each trophic level
So there is insufficient energy to support higher trophic level
