| Date | November 2019 | Marks available | 1 | Reference code | 19N.1.SL.TZ0.1 |
| Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | State | Question number | 1 | Adapted from | N/A |
Question
Figure 4(a): Average net primary productivity (kJ m–2 a–1) of selected world biomes
[Source: graphic used with the permission of Integrated Access STEM Sites, LLC]
Figure 5(b): Water-surface temperature variation across the Large Ocean Management Area
[Source: Fisheries and Oceans Canada. Reproduced with the permission of
© Her Majesty the Queen in Right of Canada, 2019]
Using Figure 4(a), identify an ecosystem that has an average net primary productivity above 30 000 kJ m–2 a–1.
Suggest one reason for the zonation seen in Figure 5(b).
Estuaries are one of the most productive ecosystems in the world, but only account for 3 % of global productivity.
State one reason why this occurs.
Outline why estuaries are highly productive ecosystems.
Markscheme
estuary/tropical rainforest.
depth of water / shallow water is warmer / shallow water is easier to warm up / deep water is cooler;
position in relation to land / distance from land;
latitude / distance from equator / northern areas are cooler / southern areas are warmer;
cold ocean currents (Labrador) coming down from the north and warm ocean currents (Gulf Stream) coming up from the south.
Do not accept ‘climate change / global warming / variation in climate / salinity /temperature’.
there are few major estuaries in the world;
they do not cover much of the Earth’s surface;
estuaries have quite a small surface area;
they represent a small proportion of the world’s ecosystems.
mix of saline and fresh water so different habitats, therefore more biodiversity, (therefore more productivity);
zonation/range of temperature/salinity results in greater habitat diversity (therefore higher productivity);
shallow water, so warmer and receive more light and therefore more productive (primary productivity);
tides/river systems/upwellings bring in nutrients that give rise to phytoplankton blooms/primary productivity;
mineral/nutrient run-off from surrounding agricultural land / nutrient run-off from surrounding watershed into the estuary;
water levels rise and fall, exposing mud flats, which are a food source for shore birds (secondary productivity);
migratory birds and whales stop here to feed, temporarily raising the secondary productivity.
Do not accept only ‘high biodiversity’.
Do not accept only ‘large/complex food webs’.
