Hello, I’m writing a lab report our class did on fruit flies. I believe the experiment is a pretty standard one – basically, we took fruit flies – normal (wild type, dominant), mutant (ebony, recessive) and another mutant (vestigial wing, recessive).

There were three control populations for the three different types of flies, starting off with 20 pregnant female flies of each single type.

Then there was single mutant competition, where cages with a population of 10 female wild types were mixed with 10 pregnant females of each mutant type.

Lastly, there was the double mutant competition. These cages started off with 10 wild females and 10 females with both recessive mutant traits – ebony color and vestigial winged.

So, we are to write a lab report on the experiment and one question I do not quite understand. It asks, ‘can the rate of selection be explained by what happened to the pure stocks (control populations)?’

The previous question asked about whether the direction of selection can be explained by what happened to the pure stocks, but I don’t understand what the question means by the ‘rate of selection’.

What exactly is a rate of selection and how does this differ from the direction of selection? I tried googling, of course, but I am still not any more sure of the meaning of the rate of selection.

Thanks for your time.