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what is a stronger selection pressure?

I don't get what a stronger selection pressure is? I saw it on one my biology papers and I didn't understand what they meant .
question : suggest why 20% of the female foxes were used for breeding but only 5 % of the male foxes
answer report :"but very few candidates realised that a stronger selection pressure could
therefore be exerted by choosing fewer males"

paper :January 2012
F215 Control, Genomes & Environment Q6
Original post by Sadilla
I don't get what a stronger selection pressure is? I saw it on one my biology papers and I didn't understand what they meant .
question : suggest why 20% of the female foxes were used for breeding but only 5 % of the male foxes
answer report :"but very few candidates realised that a stronger selection pressure could
therefore be exerted by choosing fewer males"

paper :January 2012
F215 Control, Genomes & Environment Q6

The more selective you can be with your breeding population, the closer you can get to your desired characteristic. Whilst they might be stuck with having to use as many as the top 20% of females, becasue females can only produce one litter each, they can go for the top 5% of the males because each male can sire several litters.

Obviously, the top 5% will be tamer on average than the top 20% (and still more tame than the average of the top 50% and so on). This means by breeding from these males only, you will be ratcheting up the selection pressure to drive the population towards tameness. Hope that's clear.
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Sadilla
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Original post by OxFossil
The more selective you can be with your breeding population, the closer you can get to your desired characteristic. Whilst they might be stuck with having to use as many as the top 20% of females, becasue females can only produce one litter each, they can go for the top 5% of the males because each male can sire several litters.

Obviously, the top 5% will be tamer on average than the top 20% (and still more tame than the average of the top 50% and so on). This means by breeding from these males only, you will be ratcheting up the selection pressure to drive the population towards tameness. Hope that's clear.

WOW thank you makes so much sense now :smile:

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