Energy Cycles Questions

Question 1

Explain the decrease in gross productivity as the woodland matures

Answer 1

Less light so reduced rate of photosynthesis

Question 2

Nitrogenase catalyses the reduction of nitrogen during nitrogen fixation. The reaction requires 16 molecules of atp for each molecule of nitrogen that is reduced,
Nitrogen gas is the usual substrate for this enzyme, name the product

Answer 2

Ammonium

Question 3

If scientists could transfer the gene that codes for nitrogenase to cereal plants, these cereal plants would be able to fix nitrogen. However, the scientists would expect these genetically engineered cereal plants to grow more slowly tan cereal plants than get their nitrogen from fertiliser. Explain why they would grow more slowly

Answer 3

ATP used for the reduction of nitrogen so less available for growth

Question 4

Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water

Answer 4

• growth of algae Which blocks light
• reduced photosynthesis so plants die
• saprobiotic organisms Aerobically respire
• less oxygen for fish to respire so aerobic organisms die