End of paper questions

Question 1

In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how

Answer 1

1 Light (energy) excites/raises energy level of electrons in chlorophyll;
2 Electrons pass down electron transfer chain;
3 (Electrons) reduce carriers/passage involves redox reactions;
4 Electron transfer chain / role of chain associated with chloroplast membranes / in thylakoids / grana;
Example such as chemiosmosis;
5 Energy released / carriers at decreasing energy levels;
6 ATP generated from ADP and phosphate/Pi / phosphorylation of ATP;

Question 2

Energy is transferred through an ecosystem.

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

Answer 2

1 Some light energy fails to strike/is reflected/not of appropriate wavelength;

2 Efficiency of photosynthesis in plants is low/approximately 2% efficient;

3 Respiratory loss / excretion / faeces / not eaten;

4 Loss as heat;

5 Efficiency of transfer to consumers greater than transfer to producers/approximately 10%;

6 Efficiency lower in older animals/herbivores/ primary consumers/warm blooded animals/homoiotherms;

7 Carnivores use more of their food than herbivores;

Question 3

Explain how the intensive rearing of domestic livestock increases net productivity.

Answer 3

1 Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production;

2 Fed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition;

3 Movement restricted so less respiratory loss / less energy used;
4 Kept inside/heating/shelter / confined so less heat loss / no predators;

5 Genetically selected for high productivity;