This problem is from A-Level and IB, and it is not in the NEET syllabus…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
This problem is from A-Level and IB, and it is not in the NEET syllabus. In a model of a pest, the resistance allele is recessive and has a frequency . Susceptible insects on the toxin plants lose a fraction of their fitness. With no refuge, . One generation of selection gives mean fitness , and a new frequency .
- What is with no refuge?
- What is with no refuge?
- A refuge that is half of the area cuts the effective to . What is now?
Need a reminder? The key ideaShow
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , so . with no refuge.
Plan. Find the mean fitness, then the new frequency, for each value of .
Step 1. Mean fitness. .
Step 2. New frequency. The top is . So .
Step 3. With the refuge. : . The top is . So .
Answer: ; ; .
Check. The frequency rises from to without a refuge, and only to with it. The refuge slows the rise a great deal.
Watch out. This is a model. Real resistance depends on the number of genes, the dominance and the movement of the pests.
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