Energy Transfers Flashcards
Define biomass.
- Mass of carbon (organic compounds)
- Dry mass of tissue per given area
Suggest what you should do to ensure all water is removed from a tissue sample.
- Regularly weigh and Heat (less than 100 °C)
- Until mass is constant.
What is Gross Primary Productivity?
Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis).
What is Net Primary Production?
- Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account. NPP=GPP-R.
- NPP is available for new plant growth and reproduction OR available for other trophic levels in the ecosystem, such as herbivores and saprobionts.
- kJ ha–1 year–1 OR kJ km–2 year–1 OR kJ km–3 year–1
The percentage of the light energy trapped by the producers is very low. Give two reasons why.
- Reflected/absorbed by water vapour
- Reflected from producers/wrong wavelength
- Transmitted/passes between chloroplasts/between plants/too few chloroplasts
The biomass of primary consumers is less than the biomass of producers. Explain why.
- Loss of energy/heat/less energy to be passed on
- In respiration
- In excretion/urine/carbon dioxide
- Inedible parts/indigestible parts/egestion/to decomposers
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer.
- Some light energy fails to strike/is reflected/not of appropriate wavelength
- Efficiency of photosynthesis in plants is low/approximately
- 2% efficient
- Respiratory loss/excretion/faeces/not eaten
- Loss as heat
- Efficiency of transfer to consumers greater than transfer to producers/approximately 10%
- Efficiency lower in older animals/herbivores/primary consumers/warm blooded animals
- Carnivores use more of their food than herbivores
Explain how the intensive rearing of domestic livestock increases net productivity.
- Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production
- Fed on concentrate/controlled diet/controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces/valid reason for addition
- Movement restricted so less respiratory loss/less energy used
- Kept inside/heating/shelter so less heat loss/no predators
- Genetically selected for high productivity
Describe the need for plants to both photosynthesise AND respire.
- In the dark no ATP production in photosynthesis
- Some tissues unable to photosynthesise/produce ATP
- ATP cannot be moved from cell to cell/stored
- Plant uses more ATP than produced in photosynthesis
- ATP for active transport
- ATP for synthesis (of named substance)
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur.
- High concentration of carbon dioxide linked with night/darkness
- No photosynthesis in dark/night/light required for photosynthesis/light-dependent reaction
- (In dark) plants (and other organisms) respire
- In light net uptake of carbon dioxide by plants/plants use more carbon dioxide than they produce/rate of photosynthesis greater than rate of respiration
- Decrease in carbon dioxide concentration with height
- At ground level fewer leaves/less photosynthesising tissue/more animals/less light