00:01
For this question, we're looking at the process of natural selection and looking at how the gene frequencies inside of the population start to change based on the introduction of some sort of stress.
00:13
So the beginning part of this is there's going to have to be some sort of change in the environment or some sort of stress factor.
00:23
This could be anything from a certain limitation of nutrients.
00:27
It could be an environmental change where there's something more dangerous in the environment, such as, say, an active volcano, or the amount of wind or rain increases.
00:40
Or you could have the introduction of a new predator.
00:44
There are many examples of this, but some sort of stress has to be introduced.
00:49
From there, based on this stress, you're going to cause the death of normal organisms that have not been able to adjust to these sort of stee.
00:59
Stimuli or stress.
01:01
So you're going to have the death of the normal or the unmutated population.
01:09
This is because you're going to have the increased survival of those with that advantageous mutation later.
01:20
We measure it in this way because you figure the death of the normal is going to occur typically in earlier stages.
01:27
If the nutrients inside the environment is not sufficient enough for the normal population, you're going to get these organisms dying out in an early age before they're able to reproduce.
01:42
Whereas for the survival of those with that advantageous mutation, they're going to survive first and live to that age where they're going to reproduce and allow for the heritability of this advantageous trait onto its offspring.
02:00
So here in number four, you're going to see a change in the genotype frequencies of the population first.
02:08
This is because you're going to spread that different trait or that mutation across the population.
02:16
And for five, you're finally going to see that change in the phenotype.
02:21
As this becomes more common, and you have those with that genotype starting to breed and reproduce with one another.
02:28
And you're going to get more homozygous dog.
02:31
For that phenotypic trait.
02:33
So you're going to get a greater expression of the phenotype afterwards, since your genotype can also come in that heterozygous and could possibly not be displayed.
02:44
So one way to sort of depict this, if it can be confusing how this works, is you're going to have those two populations...