Energy & Ecosystems (A Level Only)

9.A farmer wants to increase the net production of livestock. Which practice would best achieve this by reducing respiratory loss?

10.Which of the following is a valid way in which farmers can simplify food webs to increase crop yield?

11.The net primary productivity of a wheat crop is 112 500 kJ m⁻² yr⁻¹. The net productivity of insect pests feeding on the wheat is 10 000 kJ m⁻² yr⁻¹. What is the percentage efficiency of energy transfer from wheat to insects?

12.A calorimeter is used to estimate the energy stored in a dried plant sample. Which of the following is a limitation of this simple calorimeter?

13.Which of the following are ways in which plants use the sugars produced during photosynthesis? (select all that apply)

14.Which of the following statements about gross primary production (GPP) and net primary production (NPP) are correct? (select all that apply)

15.Biomass is a measure of the number of organisms present in an area.

16.Gross primary production is a rate and therefore its units include time.

17.Net primary production represents the energy available to consumers in an ecosystem.

18.The net production of consumers is also known as secondary production.

19.Match each term with its correct definition.

20.Place the steps of using a simple calorimeter to estimate the energy stored in a dried plant sample in the correct order.

21.Which of the following explains why net primary production does not represent the total plant biomass formed per year during photosynthesis?

22.Which of the following are organic compounds that living organisms need in order to respire and build their tissues? (select all that apply)

23.Which of the following statements about the fate of the sugars made during photosynthesis are correct? (select all that apply)

24.Match each biological molecule made from photosynthetic sugars with its function in the plant.

25.In aquatic ecosystems, which form of carbon do plants use to produce organic molecules?

26.The mass of carbon present in an organism or tissue sample is taken to be 50 % of the dry mass.

27.Place the steps for determining the dry mass of a plant sample using a crucible, oven and digital balance in the correct order.

28.A student uses a simple calorimeter to estimate the energy stored in a dried plant sample. The mass of water is 20 g, the temperature change is 10 °C and the mass of the sample is 0.5 g. Using Energy transferred per gram = (mass of water × temperature change × 4.2) ÷ mass of sample, what is the energy transferred per gram of the sample?

29.Which of the following units could correctly express primary productivity in an aquatic environment? (select all that apply)

30.Which of the following are valid ways in which a farmer could reduce respiratory loss in livestock to increase net production? (select all that apply)

31.A patch of rainforest covering an area of 1 km² is estimated to contain 1500 kg of biomass. What is the gross primary production of this rainforest patch in g m⁻²?

32.The biomass of aquatic algae in a tank contains a total of 5440 J of chemical energy. The tank has a volume of 4 m³. What is the gross primary production of the algae, with appropriate units?

33.The total biomass of grass growing in a 200 m² field is found to be 1000 kg. What is the gross primary production of the grass field?

34.The total solar energy received by an area of heather is 6 × 10⁵ kJ m⁻² yr⁻¹. The gross primary productivity of the heather is 4.25 × 10³ kJ m⁻² yr⁻¹. What percentage of the solar energy is converted into chemical energy by photosynthesis?

35.In a grassland ecosystem the net productivity of rabbits is 2400 kJ m⁻² yr⁻¹. The rabbits ingest 18 900 kJ m⁻² of grass per year. What is the total energy loss (F + R) of the rabbits?

36.A wheat farmer introduced toads to control insect pests. The toads ingested 10 000 kJ m⁻² yr⁻¹ of energy from the pests, lost 2000 kJ m⁻² yr⁻¹ in faeces and urine, and lost a further 7000 kJ m⁻² yr⁻¹ during respiration. What is the percentage efficiency of energy transfer from the insects to the toads?

37.A wheat farmer's crops are eaten by insect pests. The net primary productivity of the wheat is 112 500 kJ m⁻² yr⁻¹ and the net productivity of the insect pests is 10 000 kJ m⁻² yr⁻¹. What is the percentage efficiency of energy transfer from the wheat to the insects?

38.A farmer estimates that 3600 m² of farmland is required to sustain one sheep. The productivity of the grass is 19 248 kJ m⁻² yr⁻¹. Which calculation gives the energy available in the grass per year for one sheep?

39.A student measures the dry mass of plant material from two woodland sites. Which statement best explains why dry mass, rather than wet mass, should be used to compare the plant yield of the two sites?

40.The total dry biomass of a 1 m² patch of gorse was measured each year for 20 years. The biomass rose from 200 g at year 0 to 1400 g at year 20. What is the mean yearly increase in biomass?

41.Name the process by which plants convert light energy into chemical energy stored in biomass.

42.Give the term for the chemical energy stored in plant biomass after respiratory losses have been taken into account.

43.A patch of woodland contains caterpillars that ingest 2000 kJ m⁻² of chemical energy from oak leaves. They lose 1200 kJ m⁻² in faeces and urine and a further 600 kJ m⁻² through respiration. Calculate the net production of the caterpillars in kJ m⁻².

44.The wheat crop in a farmer's field has a gross primary productivity of 10 000 kJ m⁻² yr⁻¹ and loses 5500 kJ m⁻² yr⁻¹ as heat from respiration. Calculate the net primary productivity of the wheat crop in kJ m⁻² yr⁻¹.

45.An area of grass measuring 50 m² was mown and the total mass of grass cuttings was 45 kg. Calculate the gross primary production of the area of grass mowed in g m⁻².

46.Complete the sentence about the net production of consumers.

47.Name the two products of photosynthesis that are used as respiratory substrates and to build plant biomass.

48.Calculate the energy lost as heat from respiration by one square metre of grass in one year, in kJ m⁻² yr⁻¹.

49.A sunflower oil company recorded the primary production of its crop each year for five years: 150, 200, 175, 150 and 225 kJ ha⁻¹. Calculate the average primary productivity of the sunflower crop over the five-year period, in kJ ha⁻¹ yr⁻¹.

50.Complete the sentence about the equation for the net production of consumers.

51.The grass in an ecosystem has a gross primary production of 20 000 kJ m⁻² yr⁻¹ and a net primary production of 12 000 kJ m⁻² yr⁻¹. Calculate the energy lost as heat from respiration by one square metre of this grass in one year, in kJ m⁻² yr⁻¹.

52.The deer in a food chain ingests 17 874 kJ m⁻² yr⁻¹ of food. The net production of the deer is 2426 kJ m⁻² yr⁻¹. Calculate the total energy loss (F + R) of the deer, in kJ m⁻² yr⁻¹.

53.Describe how the dry mass of an organism would be calculated.

54.Explain why energy is lost in the form of faeces and urine by consumers.

55.Explain why the efficiency of energy transfer between trophic levels is never 100%.

56.Explain why it is rare to find a natural food web with more than five trophic levels.

57.In a food chain, the net production of the deer is less than the net primary production of the grass. Explain why.

58.A patch of woodland contains caterpillars that ingest 2000 kJ m⁻² of chemical energy from oak leaves. They lose 1200 kJ m⁻² in faeces and urine and a further 600 kJ m⁻² through respiration. Calculate the net production of the caterpillars in kJ m⁻².

59.The wheat crop in a farmer's field has a gross primary productivity of 10 000 kJ m⁻² yr⁻¹ and loses 5500 kJ m⁻² yr⁻¹ as heat from respiration. Calculate the net primary productivity of the wheat crop in kJ m⁻² yr⁻¹.

60.An area of grass measuring 50 m² was mown and the total mass of grass cuttings was 45 kg. Calculate the gross primary production of the area of grass mowed in g m⁻².

61.Calculate the energy lost as heat from respiration by one square metre of grass in one year, in kJ m⁻² yr⁻¹.

62.A sunflower oil company recorded the primary production of its crop each year for five years: 150, 200, 175, 150 and 225 kJ ha⁻¹. Calculate the average primary productivity of the sunflower crop over the five-year period, in kJ ha⁻¹ yr⁻¹.

63.The grass in an ecosystem has a gross primary production of 20 000 kJ m⁻² yr⁻¹ and a net primary production of 12 000 kJ m⁻² yr⁻¹. Calculate the energy lost as heat from respiration by one square metre of this grass in one year, in kJ m⁻² yr⁻¹.

64.The deer in a food chain ingests 17 874 kJ m⁻² yr⁻¹ of food. The net production of the deer is 2426 kJ m⁻² yr⁻¹. Calculate the total energy loss (F + R) of the deer, in kJ m⁻² yr⁻¹.