Chapter 13: Energy and Ecosystems

Question 1

Changes in ecosystems can lead to speciation. A high concentration of copper in soil is toxic to most plants. In some areas where the soil is pollutes with copper, populations of grasses are found to be growing. These population of grass belong to a species also found growing on unpolluted soils.
It has been suggested that a new species of grass may evolve on soil that has been polluted with copper. Explain how this new species might evolve. [5 marks]

Answer 1

1. variation
2. mutation
3. some plants have allele to survive in high concentration of copper
4. reproductive success / adapted organisms reproduce
5. increase in frequency of allele
6. no interbreeding (ie, reproductive isolation)

Question 2

Explain how the decay of dead plants results in reduced oxygen concentration and increased nitrate production [6 marks]

Answer 2

1. bacteria/fungi feed on dead matter saprobiotically
2. respiration uses up oxygen
3. converts proteins to amino acids
4. then to ammonium compounds
5. nitrifying bacteria convert ammonium compounds
6. via nitrates

Question 3

Much of indonesia is covered with forest. Large areas of forest have been cleared and planted with oil-palm trees to be used in the production of fuel.
In these forests, nitrogen in dead leaves is made available to growing plants by the action of bacteria. Describe the role of bacteria in making the nitrogen in dead leaves available to growing plants. [5 marks]

Answer 3

1. saprobionts
2. digest/break down proteins proteins
3. extracellular digestion
4. ammonia is produced
5. ammonia converted to nitrite to nitrate
6. nitrifying
7. oxidation

Question 4

Explain how farming practices increase the productivity of agricultural crops [5 marks]

Answer 4

1. fertilizers are added to soil
2. nitrogen for proteins
3. selective breeding/genetic modification
4. ploughing/aeration allows nitrification
5. benefit of crop rotation in terms of soil nutrients

Question 5

Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants [5 marks]

Answer 5

1. protein into ammmonium
2. by saprobionts
3. ammonium into nitrite
4. nitrite into nitrate
5. by nitrifying bacteria
6. nitrogen to ammonia
7. by nitrogen-fixing bacteria

Question 6

After harvesting, the remains of crop plants are often ploughed into the soil. Explain how microorganisms in the soil produce a source of nitrates from these remains [5 marks]

Answer 6

1. protein into ammonium
2. by saprobionts
3. ammonium to nitrite
4. nitrite to nitrate
5. by nitrifying bacteria