energy transfer

Question 1

Define Biomass

Answer 1

• Mass of carbon (organic compounds)
• Dry mass of tissue per given area

Question 2

Suggest what you should do to ensure all water is removed from a tissue / sample.

Answer 2

• Regularly weigh and Heat (less than 100 °C)
• Until mass is constant

Question 3

ross Primary Productivity

Net Primary Production

Answer 3

• 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

Question 4

The percentage of the light energy trapped by the producers is very low. Give two reasons why.

Answer 4

• Reflected / absorbed by water vapour;
• Reflected from producers / wrong wavelength;
• Transmitted / passes between chloroplasts/ between plants / too few chloroplasts;

Question 5

The biomass of primary consumers is less than the biomass of producers. Explain why.

Answer 5

• 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;

Question 6

Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer.

Answer 6

• 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;

Question 7

Explain how the intensive rearing of domestic livestock increases net productivity

Answer 7

• 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;

Question 8

Describe the need for plants to both photosynthesise AND respire

Answer 8

• 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);

Question 9

percentage efficiency

Answer 9

energy available after transfer/ energy available before transfer X100