QUESTION 22 (5 marks)
a) Compare the role of pioneer species in primary and secondary succession.
[3 marks]
Similarity:
Difference:
Significance:
b) Describe two ways climax communities differ from pioneer communities.
[2 marks]
QCAA guide · typeset solution
QCAA sample response and mark allocation
22a) | Similarity: All pioneer species play a key role in making an area habitable for other species. Difference: Because primary succession occurs in areas that lack habitable soils, primary pioneers must establish the soil, whereas secondary pioneers do not. Significance: Because of this, primary pioneer species tend to be lichens, algae and fungi, which have high tolerance to extreme conditions, whereas secondary pioneer species tend to be grasses that germinate rapidly. | • identifies a similarity [1 mark] • identifies a difference [1 mark] • identifies the significance [1 mark] |
22b) | Climax communities contain a higher proportion of K-strategists than pioneer communities. Climax communities are also greater in biomass. | • describes one difference [1 mark] • describes a second difference [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
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