QUESTION 8 (6 marks)
The table shows data from a transect study along a sand dune.
Zone | ||||
A | B | C | D | |
Distance from sea (m) | 0–100 | >100–150 | >150–250 | >250–300 |
Age of dune (years) | 0–50 | >50–100 | >100–125 | >125–150 |
pH of soil | 8.4 | 7.4 | 6.9 | 6.0 |
Organic matter in soil (%) | 1 | 2.5 | 5 | 30 |
Number of grass species | 2 | 4 | 6 | 2 |
Number of tree species | 0 | 1 | 3 | 8 |
a) Contrast species richness in zones A and D. Refer to data in your response.
[2 marks]
b) Infer how organic matter affects the pH of soil. Justify your response.
[2 marks]
c) Predict which zone would have the highest proportion of K-selected species. Explain your reasoning.
[2 marks]
QCAA guide · typeset solution
QCAA sample response and mark allocation
8a) | Species richness is five times higher in zone D than zone A. Zone A has two different species, whereas zone D has 10. | • identifies species richness is higher in zone D [1 mark] • provides appropriate data [1 mark] |
8b) | As organic matter increased from 1% to 30%, the pH decreased from 8.4 to 6. This suggests that organic matter lowers soil pH. | • infers that organic matter lowers soil pH [1 mark] • justifies response using data [1 mark] |
8c) | Zone D. Zone D is the oldest dune and has the highest species richness. This suggests it may be further along in succession. The number of K-selected species tends to increase as succession progresses. | • predicts zone D [1 mark] • provides appropriate reasoning [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
Compare your working with the guide above.