3.5.3 Energy and ecosytems Flashcards
How do plants use sugars from photosynthesis
As respiratory substrates
To synthesise other biological molecules eg cellulose
What is biomass
Total dry mass of tissue or mass of carbon measured over a given time in a specific area
Suggest the units for biomass
gm-2 (area)
gm-3 (volume)
How can the chemical energy store in dry mass be calculated
Using calorimetry
Energy released = SHC water x vol of water x temp increase
Why is bomb calorimetry preferable to simple calorimetry
Reduces heat loss to surroundings
How could a student ensure that all the water had been removed from a sample before weighing
Heat the sample and reweigh until the mass reading is constant
Define gross primary production GPP
Total chemical energy in plant biomass within a given area or volume
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
R = respiratory losses
Why is most of the suns energy not converted to organic matter
Not all light falls directly on chlorophyll molecule
Some of the light would be the wrong wavelength
Energy lost as heat during respiration
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 urine and faeces
Some of the organism is not consumed eg bones
Energy lost to surroundings as heat
Define primary and secondary productivity
Rate of primary or secondary production
Biomass in a specific area over a given time period eg kJ ha-1 year-1
Outline some common farming practices to increases efficiency of energy transfer
Restriction of movement
Exclusion of predators - no energy lost to other organisms in food web
Artificial heating - reduce energy lost to maintain constant body temp
General equation for % efficiency
energy converted to a useful form / total energy supplied x 100
