energy transfers and nutrient cycles Flashcards
ENERGY TRANSFERS
ENERGY TRANSFERS
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
Gross Primary Productivity
Net Primary Production
- Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
- 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;
In natural ecosystems, most of the light falling on is not used in photosynthesis.
Suggest two reasons why.
- (Light is) reflected;
Light is not absorbed on its own is not enough. - (Light is) wrong wavelength;
Accept frequency for wavelength.
Accept reference to absorbing specified wavelengths/frequencies. - (Light) misses chlorophyll/ chloroplasts/ photosynthetic tissue;
- CO2 concentration or temperature is a limiting factor
The biomass of primary consumers is less than the biomass of producers. Explain why.
- Loss of energy/heat / use of energy / less energy to be passed on;
- In respiration;
- In excreta / excretion / urine / carbon dioxide;
Inedible parts / indigestible parts / egesta / 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 / confined 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;
NUTRIENT CYCLE
NUTRIENT CYCLE
Explain what is meant by the term carbon sink.
- Takes up / locks up / stores carbon / carbon dioxide (for a long time) / eq ;
- Named example e.g. peat / coal / limestone / trees / fossil fuel / chalk / shells ;
Explain what is meant by the term global warming.
- Increase in {temperature of earth’s surface / mean global temperature / eq};
- Carbon dioxide is a greenhouse gas / due to an increase in greenhouse gases ;
- (Which) {trap / reflect back} {heat / long wave / infra red} (in the atmosphere) ;
- Reference to an {increased / enhanced} greenhouse effect ;
- Reference to valid {effect / consequence} e.g. melting ice caps, flooding, climate change ;
Describe the role of saprobionts in the nitrogen cycle.
- (use enzymes to) decompose proteins / DNA / RNA / urea;
- Producing / releasing ammonia / ammonium ions;
