QUESTION 57 (6 marks)
Site A is a newly exposed rock surface after a glacier retreats. Site B is a burnt grassland where soil, roots and a seed bank remain.
a) Identify the succession type at each site and justify each choice. [4 marks]
b) Explain why early recolonisation is likely to be faster at B, with other conditions similar. [2 marks]
Practice marking scheme
Answer
a) A: primary, because established soil is absent. B: secondary, because soil remains. b) Existing soil and surviving seeds/roots provide resources and sources for regrowth.
Working
Primary succession begins on a substrate without established soil. Secondary succession follows disturbance where soil remains. At B, organisms do not first have to establish a soil layer, and surviving seeds or roots can regenerate. Thus initial establishment may be faster than on bare rock, although actual rates also depend on environmental conditions.
Marking criteria
- Identifies A as primary succession. [1 mark]
- Justifies A by absence of established soil. [1 mark]
- Identifies B as secondary succession. [1 mark]
- Justifies B by persistence of soil. [1 mark]
- Links existing soil to easier establishment. [1 mark]
- Links surviving seed bank/roots to rapid regrowth. [1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusCompare your working with the guide above.