Okay, so now we're going to talk about artificial selection. And the reason we're going to talk about this is because this is actually an applicable reason to use the calculations we talked about before, heritability. So, what is artificial selection? That's the process of choosing specific individuals for some type of phenotypic breeding purpose. For instance, if a farmer like a dairy farmer, who produces cows for milk, wanted to increase the milk production of their cows, they would try to make specific individuals in order to increase that milk production. But before they start mating these cows, right, that's a huge undertaking to make these cows for bigger or for more milk production. They want to make sure that it's actually going to work. And so geneticists can actually tell you, you know, is this likely to increase milk production? And how they do that is they use Narrow Sense Heritability to predict the impact of breeding. Now, why Narrow Sense Heritability? Well, because Narrow Sense Heritability is measuring the likelihood that a trait is actually attributed to genetics and not inheritance. And it's also the ability because narrow sense heritability measures additive, right, then that is measuring the ability to inherit this dominant or recessive allele that's really going to impact the production of milk. So the higher the h2 value, so because h2 is a measure between 0 and 1 so that's going to be the closer to 1. So if you calculate this ht value, the closer to 1, then, the more likely that the breeder will observe a change. The more likely that that's going to result in potentially milk production. So there are 2 formulas. The first we talked about before, and that's just the Narrow Sense Heritability Formula. Right. This is what we talked about previously, but and sometimes you know this information. It's like on a test or quiz setting, you might be actually given this information, But if you're a breeder, you probably don't already just have the amount, additive variance that's contributed to the production of milk. Right? Like, you most likely don't have that. So there's a second formula that you can use to calculate narrow sense heritability, and that actually is this one. And it's r over s. And so, r is the mean of the offspring, so how much milk in volume the offspring produces versus the overall mean of the population that you started with, divided by the mean of the parent, so how much the mother produced essentially, versus the overall mean. So you do have to do at least one mating to get this. Right? And this is called the selection response, and the selection differential. And so, sometimes on I don't know which one you'll be given. Right? Like, if you're asked to do this on a test or quiz, you could be given this, or you could be given the means and asked to solve it this way. But essentially, the question would be, how likely is it that this trait could be inherited or that a breeder could select for this trait in the population. Either way, what you're looking for is an ht value close to 1. The closer to 1 it is, the more likely that it can be inherited. So if we go back to these numbers, which we talked about before. Right? We have body fat, had an h2 value of 0.18 and, we had body length as an h2 value of 0.11. I think this is right. Now, which of the following two traits will respond best to a selection by a breeder? Right? So it's the higher h2 value. So in this case, it would be this one, which would be body fat, because it's closer to 1. But really, to be honest with you, both of these are very low. Right? So you would need much higher h2 values before a breeder is like, okay, I will try to actually select for this trait. So make sure you understand this formula and this one and how you use that to determine whether or not a breeder, you know, whether or not that trait can be inherited or not for artificial selection purposes.
So with that, let's now turn the page.
