| Date | May 2017 | Marks available | 4 | Reference code | 17M.3.SL.TZ1.16 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Discuss | Question number | 16 | Adapted from | N/A |
Question
Freshwater invertebrates were sampled by students at three sites along a river in central France. The animals were identified and counted. The diversity of each site can be compared using Simpson’s reciprocal index.
Simpson’s reciprocal index is given by the following formula:
Calculate the diversity of site C. Working should be shown.
Site A has a higher Simpson’s reciprocal index than Site B showing that its diversity is higher.
Explain the reason that ecologists consider Site A to have a higher diversity than Site B, despite both sites having six different species present.
Discuss the advantages and disadvantages of in situ conservation methods.
Markscheme
a. 
b. = 3.56 «allow 3.55»
a. the species in Site A are more evenly represented than site B
b. site B has a large number of one species «but very few in the other 5»
c. Simpson’s reciprocal index is a measure of species evenness as well as species richness
Advantages:
a. conservation in the natural habitat / ecosystem
b. the species will have all the resources that it is adapted to
c. the species will continue to evolve in their environment / can maintain genetic diversity
d. the species have more space so a bigger breeding populations can be kept
e. it is cheaper to keep an organism in its natural habitat
f. established food webs/ species interactions can be maintained
Disadvantages:
g. it is difficult to control illegal exploitation «eg poaching»/harder to monitor populations
h. the area may need restoring / may be required for other purposes
i. alien species are difficult to control
j. species close to extinction are harder to conserve
k. management/protection may represent a significant cost
