Study Fig. 7, which shows the location of the Sahara Desert. [Figure 7]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2016). The mark or mark type is shown in brackets.

1. [1] (a) (i) 5300 – 5600 kms
2. [2] (ii) close to/on and around Tropic of Cancer/23.5°N
3. North Africa;
4. Any 3 of Mauritania/Mali/Algeria/Niger/Libya/Egypt/Sudan/Chad
5. [3] (iii) Describe:
6. Hot in summer/July or Jan (Nth or Sth hemisphere);
7. cooler in winter/Jan or July (Nth or Sth hemisphere); ;
8. summer average around 30 °C-40 °C/temperature up to 50 °C;
9. winter average around 15-20 °C/temperature can go as low as 0 °C or below;
10. 250 mm of rain or less; etc.
11. High diurnal temperature range/hot during the day and cold at night;
12. Hot and dry/low rainfall/arid conditions = 1 mark
13. [4] Explain:
14. Overhead sun/high angle of sun in summer/direct sunlight;
15. Clear skies/lack of cloud cover;
16. High atmospheric pressure;
17. Descending air;
18. Little evaporation of moisture/little transpiration;
19. no condensation;
20. winds blow over large areas of land/they are mainly inland so winds are dry;
21. rain shadow effect (or description);
22. cold ocean current;
23. etc.
24. [3] (b) (i) Ideas such as:
25. steep/vertical slopes/cliffs;
26. mainly bare rock;
27. jointed rock/cracks;
28. small rocks/scree/loose deposits at base of steep slope;
29. forms 45 degree angle;
30. scattered/sparse vegetation/barren;
31. short/small/low plants/little trees;
32. shrubs/ bushes;
33. orange/red/brown/rust coloured rock;
34. layers/sedimentary;
35. etc.
36. [5] (ii) Ideas such as:
37. Seeds/plants remain dormant during long dry spells/when it doesn't rain;
38. Only flowering for a short period of time after rain;
39. Waxy leaves;
40. Narrow/spiky leaves/small leaves;
41. Tap roots/long roots;
42. Wide spreading roots;
43. Some plants/cacti store water;
44. Light colour; to reflect sunlight (dev)
45. etc.
46. [7] (c) Levels marking
47. Level 1 (1-3 marks) Statements including limited detail which describe the characteristics of mangrove swamps and/or explain why they form in some areas.
48. Level 2 (4-6 marks) More developed statements which describe the characteristics of mangrove swamps and/or explain why they form in some areas.
49. Level 3 (7 marks) Comprehensive and accurate statements which describe the characteristics of mangrove swamps and explain why they form in some areas.
50. Content Guide/for information: Mangroves swamps are areas of vegetation found along sheltered tropical coastlines and estuaries between 32°N and 38°S where there is a large area between high and low water mark. They are made up of different species of evergreen mangrove trees and other plants. Mangroves need to live in salty water as they are halophytes. They only grow in areas where the temperature remains above 20 °C and the seasonal temperature range should not exceed 5°C. The areas where they grow should be calm with no strong waves or tidal currents. Mangrove trees are able to withstand being covered twice a day by saltwater. They have specially adapted aerial and salt filtering roots and salt excreting leaves that enable them to occupy the wetlands where other plants cannot survive. They prop the tree up with their prop roots and take in oxygen at low tide with their aerial roots. Mangroves are the home to a diverse number of species including fish, birds, frogs, snakes, insects and crocodiles. Mammals also live in these areas, ranging from small animals like swamp rats and monkeys to large carnivores like tigers. (Mangroves protect coastlines from erosion by acting as a natural barrier and flood defence).
51. Characteristics: Muddy; Tidal; Trees/bushes; Tropical; Shallow; Many different species of trees/prop roots/aerial roots; Prefer a large tidal range; Prefer little undercurrent tidal action; No: Place specific reference is not needed as this is not a case study.