| Date | November 2010 | Marks available | 3 | Reference code | 10N.3.SL.TZ0.6 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Evaluate | Question number | 6 | Adapted from | N/A |
Question
Many factors affect the distribution of animal species including weather patterns. The mosquito Anopheles is a carrier of malaria, a disease that kills one to two million people annually. The eggs of the mosquito are laid in water and they hatch out as larvae before turning into adult mosquitoes. A study was undertaken to look at the influence of weather patterns on the incidence of bites on children. Being bitten increases the risk of catching malaria.
The graphs show human biting rates (HBR) by Anopheles gambiae and Anopheles funestus and precipitation over the study period.
Evaluate the effect of increased precipitation on HBR for both species.
Markscheme
a. both species show relationship between elevated precipitation and higher HBR (e.g. between week 0 and week 8 / week 100 and week 108);
b. there is a lag between the period of precipitation and the increase in HBR;
c. sometimes elevated precipitation does not lead to peaks of HBR (e.g. week 27);
d. precipitation has a greater effect on Anopheles gambiae/A. gambiae;
Examiners report
Almost all candidates gained 1 mark for stating that both species show a relationship between elevated precipitation and higher HBR and many received a second mark, often for commenting on the lag between precipitation and increase HBR. Some were able to identify other effects as well.
