Hi. It's Mr. Andersen and in this podcast I'm going to talk about microevolution which
is simply change in the allele frequency of a gene pool. Contrast that with macroevolution
which is large scale over a long period of time, speciation. They're essentially the
same thing. But microevolution is just at the small level. So let's look at a population
here. Let's say we have a really small population. This population just has 10 individuals. And
5 of them, we'll say this one, this one, this one, this one and this one have red hair because
they have two genes for red hair. But the other ones are not red heads. So we'll say
half the people have red hair. Half the people don't. And so that would be our population.
But if I were to take all of those genes and just kind of throw them in a pile, that would
be our gene pool. And that's what life does. We basically have a population. There is sex,
which is a shuffling of the gene pool. And we create another generation. And another
generation. And another generation. It's almost like shuffling a deck of cards over and over
and over again. Dealing out two at a time to make your population. Then we shuffle it
again at the next generation. And so microevolution is if we ever change the allele frequency.
What's the allele frequency? Well let's say red, it looks like red is recessive. And since
there are 14 red, that means our allele frequency is 14 out of 20 or 0.7. And our blue or non-red
is going to be 0.3. And so with each generation if we ever have change in the allele frequency,
then evolution has occurred. Microevolution. And there are only 5 things that cause microevolution.
And that's why my hand was on the first slide. Because if you can remember all 5 of those
things, you can remember, or all 5 of your fingers you can remember the 5 causes of evolution.
And so basically look at you're hand for just a second. This one has a massive ring on it.
But we're going to go through each of those. And so the first thing that can cause change
in the allele frequency is going to be small sample size. So on your hand that would be
your small finger. And so let's say that this is our population. Original population. Again
we have 10 individuals. So we have 20 total genes. But let's say those are randomized
for the next group. So through sex we get a shuffling of those genes. And so in our
second generation, just due to chance, the allele frequency is going to change. Or it's
going to drift away from its original allele frequency. And so as we watch these being
selected, time after time after time, the original population is used to create the
second generation. But it's the allele frequency here that sets up the third. Which eventually
sets up the fourth. Which eventually sets up the fifth. And I'm not going to wait for
this animation to finish. But basically you can see that the allele frequency is starting
to drift away, just due to random chance. In other words if you flip 1,000 coins, are
about half of them going to be heads and half of them tails? Yeah. But if you flip 5 coins
or 6 coins are half of them going to be heads or tails. No. Because chance takes over. And
so let me show you a computer simulation of that. Let's say we do alleles here and then
we do it over time. Just using a computer simulation with an n of 20. So 20 individuals.
You can see the allele frequency started at 0.5 and 0.5 but it drifts away. If in this
computer simulation we move the number to 200 or to 2000 then those alleles stay at
about the same rate. And so as long as the population is large and not small, then microevolution
shouldn't occur. Should stay and the specific same one. Next thing that can cause microevolution
is non-random mating. They way I remember that is this finger right here is your ring
finger. It's got a ring on it. And that stands for a mate. And so basically if we have non-random
mating that can cause microevolution. Example, let's talk about humans. This is Charles II.
So basically if you look at this pedigree, there's weird stuff going on. So right here
we have a niece marrying an uncle or having kids with an uncle. And see, we see that occur
here. And so we have inbreeding. So we've got people who are choosing mates based on
their last name or that they're in the same family. They have royal blood. But that also
kind of keeps the money in the family. And so this is now non-random mating. And so evolution
occurs. Microevolution occurs. And these people develop what's called the Hamburg chin, that
almost made it tough to eat. Or let's talk about blue eyes. So blue eyes in humans showed
up. It's a mutation. But a lot of people find blue eyes attractive. So they're choosing
a mate based on the color of their eyes. And so the color of all human's eyes went from
just one person having blue eyes to I think in the U.S. something like 10 percent of the
population has blue eyes. And so it's a much higher rate. So microevolution has occurred
because we have non-random mating. You're choosing a mate based on their appearance.
If we go to the third finger. So your middle finger. The M in your middle finger should
remind you of the word mutation. And so mutations can cause microevolution as well. And so this
is DNA. Remember DNA makes RNA makes proteins make you. And so if we get a change in the
letter, that causes a change in the protein. So this would be a mutation that causes the
hemoglobin protein to mutate. And it causes sickle cell anemia. So people whose blood
cells have this sickle shape appearance. Now remember that gave them advantage if you live
in an area where there's a lot of malaria. But that mutation, since it's a new allele
is going to change the allele frequency as well. The fourth one, so our pointer finger,
the pointer finger should remind you that some individuals can leave a population. And
some of them can come into a population. And we call that gene flow. And so if you have
individuals leaving a population or new individuals coming in that's clearly going to change the
allele frequency as well. And so a great graph here. This is looking at mitochondrial DNA
in humans in different places on our planet. And so we can see that all humans originated
in Africa. And then we had a migration that went to Australia. A second migration that
created the people in Asia. And eventually the Middle East and then spread into Europe
as the Ice Age started to move back. But as those populations, if there wasn't connectivity
between them, that's definitely going to change the allele frequency. And that's one reason
that we see humans having different appearances depending on where they exist on our planet.
And so again the pointer finger means leaving or coming in. And so what is the fifth thing
that can cause microevolution? What is the thumb? Well thinking back to, you know, the
Romans you either survive or you die. Death or life. And so you should think about what's
called natural selection. And so nature is basically looking at the way you are. And
it's voting thumbs up, you survive. Or thumb's down, you die. An example, this is the tuberculosis
bacteria. And so if we treat that with an antibiotic we're going to kill all of the
bacteria that aren't susceptible to, that ARE susceptible to the antibiotic. And so
over time those bacteria are going to gain antibiotic resistance. And so they're doing
that by nature selecting or killing some of them, thumb's down. And then ones that survive
are then able to pass those genes on. So again, there are five things that can cause microevolution.
Can you remember the five? They are small sample size. Non-random mating. Mutation.
Gene flow or emigration or immigration. And then natural selection. And if you've got
all of those, thumbs up to you.