A wildlife unit is considering release of male mosquitoes altered so that their female offspring cannot survive to adulthood. Fig. 1 shows the release cage ...
Question 1 Report
A wildlife unit is considering release of male mosquitoes altered so that their female offspring cannot survive to adulthood. Fig. 1 shows the release cage and mosquito trap used to monitor the local population. Table 1 shows mean numbers of adult female mosquitoes caught each week in areas 1 km from the release site and 15 km away. Both areas had similar temperature and rainfall.
Table 1
| Week | Females caught near release site | Females caught 15 km away |
|---|---|---|
| 0 | 84 | 81 |
| 4 | 39 | 79 |
| 8 | 18 | 76 |
(a) Describe the change in female mosquito numbers near the release site. [2]
(b) Use Table 1 to suggest whether the altered males affected the population. [2]
(c) Describe how the unit could check that the same trapping method was used in both areas. [3]
(d) Suggest why releasing only male mosquitoes is important. [3]
Answer Details
(a) Near the release site, female mosquito numbers decreased from 84 in week 0 to 18 in week 8.
\[84-18=66\]
This is a decrease of 66 mosquitoes over 8 weeks. [2]
(b) Female numbers fell strongly near the release site, but stayed similar 15 km away, changing only from 81 to 76. Since temperature and rainfall were similar in both areas, this comparison suggests that release of altered males caused the local decrease. [2]
(c) Use identical traps in both areas and leave them in place for the same length of time. Use the same number of traps and sample on the same dates. These controls make differences in catches less likely to be due to different methods. [3]
(d) Male mosquitoes do not bite humans. Female mosquitoes bite and may transmit disease. Released males can mate with females and pass on the altered gene, while avoiding the added disease risk that would come from releasing biting females. [3]
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