| 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.
\(N\):
\(n\):
Discuss three reasons for the conservation of biodiversity in rainforests.
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)
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)
Examiners report
Candidates had a difficult time stating precisely what N and n stand for in the Simpson Diversity Index.
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.
