| Date | May 2016 | Marks available | 2 | Reference code | 16M.1.SL.TZ0.2 |
| Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | Explain | Question number | 2 | Adapted from | N/A |
Question
Figure 3: A simplified diagram of the Lake Shergar area.
Figure 3
[Source: © International Baccalaureate Organization 2016]
The lake provides a water supply for the local population.
Outline why this lake may be considered an open system.
Identify two outputs from this lake.
With reference to Lake Shergar, explain what is meant by natural income.
With reference to the cattle in the area, explain how the maximum sustainable yield could be calculated.
Nitrates and phosphates from nearby farms may drain into the lake. Identify a strategy for managing this pollution at each of the following levels:
Markscheme
it exchanges matter and energy (with its surroundings).
[1 max]
water flow/river Nia
evaporation
infiltration/groundwater flow
fish/biota
water (supply for local communities)
hydropower /electricity /energy from the dam
oxygen from plants
heat
Award 1 mark for any two correct responses. No mark for only one correct response.
Accept any other reasonable suggestions.
Do not accept only ‘energy’ (as examples of matter and energy are required).
[1 max]
natural income is the annual growth/yield in natural capital /natural income is derived from natural capital;
natural income are marketable commodities produced by the lake / lake provides a yield or harvest of goods/services.
Example:
goods such as water for the village/crops/cattle
goods such as fish/water plants
services such as flood protection /power or electricity from dam.
Do not accept natural income as money/revenue for selling resources or definition of sustainable yield.
[1] for explaining natural income and [1] for providing one example.
[2 max]
it is the maximum rate that it can be exploited without depleting the stock;
for example calculating the annual gain in biomass (of the cattle/stock)/annual growth of the cattle minus death;
sustainable yield = (total biomass/energy at time t + 1) − (total biomass/energy at time t).
[2 max]
Do not credit use of same management strategy more than once.
Do not accept just ‘contour ploughing/creating barriers/filter water/legislation/change behaviour/clean up’ without explanation.
Do not accept use of natural/organic fertilizers or addition of limestone / calcium carbonate (which releases phosphates from the sediments).
[3 max]
Examiners report
The majority of candidates correctly answered this question.
Most candidates were able to clearly identify two outputs from the lake.
Responses varied widely. A common error included referring to natural income as monetary income. In some cases, no reference was made to the lake as requested.
Few candidates explained how maximum sustainable yield (MSY) could be calculated. Many candidates confused MSY with carrying capacity.
Responses varied widely with some candidates clearly identifying 3 correct strategies, however many responses lacked sufficient detail e.g. answers just stated ‘legislation’ or ‘clean up’.
