Year Mean wing length (mm) Before storms 9.1 After storms 11.4 The table records the average wing length of an insect population before and after a series o...
Question 1 Report
| Year | Mean wing length (mm) |
|---|---|
| Before storms | 9.1 |
| After storms | 11.4 |
The table records the average wing length of an insect population before and after a series of storms that blow weak fliers away. Which conclusion is best supported?
Answer Details
The storms act as a selection pressure that removes weak fliers, which tend to be the shorter-winged insects. Longer-winged insects fly more strongly, so more of them survive and reproduce and pass on their alleles for longer wings, which is why the mean wing length rises from 9.1 mm to 11.4 mm. The best-supported conclusion is therefore that insects with longer wings survived and reproduced, so the mean rose. Insects do not grow longer wings because they need them, the storms do not create a mutation for longer wings, and wind cannot stretch the wings of individual insects. The population mean shifts because selection changes which alleles are passed on, not because individuals change during their lives.
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