june 2022 biology paper 2

Question 1

equation for net productivity of consumers

Answer 1

N= I - (F+R)

Question 2

Apart from temperature and pH, give two variables the scientist would have controlled
when preparing the liquid medium cultures (2)

Answer 2

-concentration
-volume
of bacteria

Question 3

assumptions of hardy weinberg equation (2)

Answer 3

-no immigration
-no mutations

Question 4

Nitrogenase catalyses the reduction of nitrogen during nitrogen fixation. The reaction
requires 16 molecules of ATP for each molecule of nitrogen that is reduced.
When ammonia inhibits nitrogenase activity, nitrogen-fixing bacteria may benefit.
Explain how (2)

Answer 4

-less ATP used
-more ATP available for growth

Question 5

Farming cattle for humans to eat is less efficient than farming crops because of
energy transfer.
Explain why. (2)

Answer 5

-energy lost in respiration/faeces/excretion
-energy lost between trophic levels.