| Date | May 2011 | Marks available | 1 | Reference code | 11M.3.HL.TZ2.1 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Describe | Question number | 1 | Adapted from | N/A |
Question
A study was undertaken of the evolution of two species of wasps, one the parasite of the other. The parasite queen, Vespula squamosa, kills the host queen, Vespula maculifrons, and takes over her role in the colony. Data was compiled for 13 colonies of V. squamosa and 37 colonies of V. maculifrons to analyse the genetic structure of the two species.
Each point on the graphs represents the genetic distance and geographic distance between a pair of colonies. The genetic distance indicates the number of differences in specific DNA markers between a pair of colonies. The results are shown below.
Determine the greatest genetic distance between any pair of colonies of V. squamosa.
Identify the greatest geographic distance between any pair of colonies of V. maculifrons.
Describe the relationship between the geographic distance and genetic distance in the two species.
Compare the two species in terms of genetic distance between the pairs of colonies.
Markscheme
0.26 (arbitrary units) (units not required)
123 km (accept answers in the range of 122 km and 124 km)
none / low correlation / non-significant / OWTTE;
less data/fewer results/less variation at 60/70 km distance;
both show genetic differences (between all pairs of colonies);
both have (highly) variable/wide range of genetic distance;
similar mean/average genetic distance;
V. maculifrons has a greater range than V. squamosa; (vice versa)
Examiners report
Parts (a) (i) and (ii) were intended to key the candidates in to the data and give two relatively easy marks. Most scored them, but those that did not often then scored poorly on the rest of this question.
Parts (a) (i) and (ii) were intended to key the candidates in to the data and give two relatively easy marks. Most scored them, but those that did not often then scored poorly on the rest of this question.
Part (b) was perhaps slightly misleading, given that the expected answer is that there is not clear relationship between genetic and geographic distance in the pairs of colonies.
Some candidates overcomplicated their answers to (c) by including differences in geographic distance. This was not intended and the two available marks could be scored relatively easily by giving similarities and differences between the two species in the genetic difference between pairs of colonies.
