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Date November 2013 Marks available 1 Reference code 13N.3.SL.TZ0.21
Level Standard level Paper Paper 3 Time zone TZ0
Command term State Question number 21 Adapted from N/A

Question

\[D = \frac{{N(N - 1)}}{{\sum {n(n - 1)} }}\]

State what \(N\) and \(n\) stand for in this formula.

 

\(N\):

 

\(n\):

[1]
b.i.

Discuss three reasons for the conservation of biodiversity in rainforests.

[3]
b.ii.

Markscheme

\(\left. {\begin{array}{*{20}{l}} {N:}&{{\text{total number of organisms of all species found/in population;}}} \\ {n:}&{{\text{number of organisms of a particular species;}}} \end{array}} \right\}\) (both needed)

b.i.

ethical: life should be respected / cultural importance for (local human indigenous) population / (human indigenous) population’s ability to live sustainably within ecosystem might be affected / richness for future generations;

ecological: native species might be replaced by alien species / extinction of one species can lead to the extinction of many others / interdependency of species may be disrupted/negative effects on food chains /soil erosion/floods occur with deforestation / rainforests act as a carbon sink which helps reduce global warming;

economic: medicines or materials not found yet / genes of wild species need to be preserved / ecotourism improves local economy/encourages local conservation / plant sources of pharmaceuticals lost if species extinct / crops may be improved with alleles from wild plants;

aesthetic: loss of beauty of wild / inspiration for artists;

(Words in italics alone are not worth marks)

b.ii.

Examiners report

Candidates had a difficult time stating precisely what N and n stand for in the Simpson Diversity Index.

b.i.

This question on reasons for conserving rainforests has been answered frequently and candidates were often able to get the full 3 marks for giving a reason that was ethical, ecological, economic or aesthetic in nature.

b.ii.

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.4 Conservation of biodiversity
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