During a long-term drought, both male and female large...

During a long-term drought, both male and female large ground finches developed larger and larger beaks over several generations. What type of selection is this an example of? sexual directional stabilizing disruptive

Transcript

00:01 During a long -term drought, both male and female large ground finches developed larger and larger beaks.

00:07 What type of selection is this? sexual, directional, stabilising, or disruptive.

00:14 Okay, so let's start by ruling out sexual selection.

00:17 Sexual selection is where individuals with particular traits get to mate, not because of environmental pressures, but because of pressures from other individuals.

00:28 So, for example, in peacocks, a big peacock tail is not adaptive to the environment, but because it is so preferential to female peacocks, it has evolved anyway.

00:41 So that's sexual selection.

00:43 But this is because of a drought, so this isn't sexual selection, this is just regular, natural selection.

00:49 The other three options are types of selection, which i will show.

00:54 So we're going to have this population.

00:57 Here's beak size, nice polygenic traits, lots of genes involved, so it's got continuous variation.

01:06 And then let's apply these different selections.

01:09 Starting with d.

01:10 Disruptive selection.

01:12 Disruptive is where the average value is selected against, and the extreme values are selected for.

01:20 So it's not good to be average, it's good to be somewhere on the extreme.

01:24 So what this does is you end up with a bimodial results.

01:32 Less of the average, more of the extremes.

01:35 This isn't what we're seeing here, because the beaks have just got larger and larger...

Question

During a long-term drought, both male and female large ground finches developed larger and larger beaks over several generations. What type of selection is this an example of? sexual directional stabilizing disruptive

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