CH13 Energy transfer Flashcards
How do plants use sugars from photosynthesis
Primarily as respiratory substrates
To synthesise other biological molecules - cellulose
What is biomass
Total dry mass of tissue or mass of carbon measured over a given time in a specific area
Units for biomass
area - gm-2
volume - gm-3
How can chemical energy store in dry mass be estimated
Using calorimetry
Energy released = specific heat capacity of water x volume of water x temperature increase of water
Why is bomb calorimetry preferable to simple calorimetry
Reduces heat loss to surroundings
How to ensure all water is removed from a sample before weighing
Heat sample and reweigh until 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
Relationship between GPP and NPP
NPP = GPP - R R = respiratory losses
Why is most of Sun’s energy not converted to organic matter
Most solar energy 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 and photosynthesis
How can 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 the food chain
Energy lost in nitrogenous waste
Some of the organism not consumed
Energy lost to surroundings as heat
Define primary and secondary productivity
Biomass in a specific area over a given time period
kJ ha-1 year-1
Common farming practices 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 useful form (J) / total energy supplied (J) ] x 100
