For this example, it says, in each situation below, identify what type of selection is being discussed, then predict how the average phenotype in the population will change as a result of this selection. If you do not expect the population to change, write no change. Alright. So let's dive right in. A says, in a population of ginkgo trees, trees that are very short do not get adequate sunlight.
Well, trees that are very tall are subject to more wind damage. Medium height trees have the highest fitness. Well, what type of selection does that sound like? To me, it sounds like stabilizing selection. And in stabilizing selection, how would you expect the average phenotype in this population to change over time?
Well, I'm going to say no change. Right? That's the idea of stabilizing selection. The average phenotype is stabilized because it has the highest fitness and it's the extremes of the population that are removed. Alright.
B says then, in a population of oysters, light-colored oysters can camouflage on shallow rocks, while dark oysters can camouflage against dark shadows. Medium-colored oysters are easily caught as prey. Well, what type of selection does that sound like? I'm going to say disruptive. Right here, the average phenotype is bad, and it's the extremes that are better.
So what's the change to the population that we expect to see? I'm going to say this is going to increase that phenotypic variation. Right? So here I expect to see more dark oysters, more light oysters, and fewer of those medium or average oysters. Alright.
Our next one, c, well, it says over the course of many generations, servals, a medium-sized wildcat native to sub-Saharan Africa, have evolved from having normal-sized ears to having large ears optimized for hunting. Alright. So what type of selection does it sound like happens there? I'm going to call that directional. And what's the change that we see to that average phenotype?
Now I'm going to say big ears. Having big ears is something I know about. Alright. So these cats are getting bigger ears over time. That's a directional change in terms of that phenotype.
It's changing in a very clear way, and so we call that directional selection. Alright. We'll practice this more, and practice problems come up. Give them a try.