Energy Transfers Flashcards
Define biomass (2)
- Mass of carbon
- Dry mass of tissue per given area
Suggest what you should do to ensure all water is removed from a tissue / sample. (2)
- Regularly weigh and heat
- Until mass is constant
Define Gross Primary Productivity (1)
- Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
Define Net Primary Production (2)
- 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
The percentage of the light energy trapped by the producers is very low. Give two reasons why. (2)
- Reflected / absorbed by water vapour
- Wrong wavelength
- Transmitted / passes between chloroplasts
In natural ecosystems, most of the light falling on producers is not used in photosynthesis. Suggest two reasons why (2)
- Light is reflected
- Light is wrong wavelength
- Light misses chlorophyll
- CO2 concentration or temperature is a limiting factor
The biomass of primary consumers is less than the biomass of producers. Explain why. (4)
- Loss of energy
- In respiration
- In excretion
- To decomposers
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer. (6)
- Some light energy is reflected
- Efficiency of photosynthesis in plants is low
- Approximately 2% efficient
- Respiratory loss / excretion
- Loss as heat
- Efficiency of transfer to consumers greater than transfer to producers
- Efficiency lower in primary consumers
- Carnivores use more of their food than herbivores
Explain how the intensive rearing of domestic livestock increases net productivity (5)
- Slaughtered while young so more energy transferred to biomass
- Fed on controlled diet so higher proportion of (digested) food absorbed
- Movement restricted so less respiratory loss / less energy used
- Kept inside so less heat loss / no predators
- Genetically selected for high productivity
Describe the need for plants to both photosynthesise AND respire (6)
- 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. (6)
- High concentration of carbon dioxide linked with night/darkness
- No photosynthesis in dark
- (In dark) plants respire
- In light, plants use more carbon dioxide than they produce
- Decrease in carbon dioxide concentration with height
- At ground level fewer leaves/less photosynthesising tissue
Name 2 saprobionts (2)
- Bacteria
- Fungi
How can you calculate net primary production? (1)
NPP = GPP - R
How can you calculate the net production of consumers? (1)
N = I - (F + R)
