Paper 2

• Give the location of the receptors that detect a decrease in blood pressure

  Aorta
• Give three reasons for the low efficiency of energy transfer from secondary consumers to tertiary consumers in an ecosystem.

  1. Heat (loss) from respiration;
  2. (Food) not digested OR Not all eaten;
  3. Excretion;
• Genetic fingerprinting using STRs requires amplification of the of the STRs using the polymerase chain reaction (PCR). The short base sequences either side of a specific STR are known.

  Explain the importance of knowing these base sequences in PCR.

  1. (For) primers;
  2. (To produce) a complementary base sequence;
• Describe how the mark-release-recapture method could be used to determine the

  population of A. aegypti at the start of the investigation.

  1. Capture/collect/sample, mark and release;
  2. Leave time for mosquitoes/Aedes to disperse before second sampling/collection;
  3. (Population =) number in first sample x number in second sample divided by number of marked in second sample/number recaptured;
• The biomass of a plant represents its dry mass/ mass of carbon.
• Farming cattle for humans to eat is less efficient than farming crops because of energy transfer.

  Explain why.

  1. Energy lost between trophic levels;
  2. Energy lost via respiration/excretion/faeces;
• Give two reasons why transmission across a cholinergic synapse is unidirectional.

  1. (Only) the presynaptic knob has neurotransmitter;
  2. (Only) the postsynaptic membrane has receptors;
• ADH causes the addition of channel proteins (aquaporins) into the membrane of the collecting duct in the kidneys.