Microevolution

Summary

In this educational podcast, Mr. Andersen delves into the concept of microevolution, which involves changes in allele frequency within a gene pool. He contrasts it with macroevolution, emphasizing the small-scale, short-term nature of microevolution. The discussion covers five key factors causing microevolution: small sample size, non-random mating, mutation, gene flow, and natural selection. Each factor is illustrated with examples, from genetic drift in small populations to the evolution of antibiotic resistance in bacteria, providing a clear and engaging explanation of evolutionary processes.

Takeaways

• 🧬 Microevolution refers to changes in the allele frequency within a gene pool, as opposed to macroevolution which involves large scale changes over a long period of time leading to speciation.
• 🔄 The process of microevolution involves the shuffling of genes through sexual reproduction, creating new generations and potentially altering allele frequencies.
• 🔢 Allele frequency is calculated by the number of specific alleles divided by the total number of alleles in the gene pool, and changes in this frequency indicate microevolution.
• 👶 Small sample size in a population can lead to random changes in allele frequency due to the influence of chance, as seen in the analogy of flipping a small number of coins.
• 💍 Non-random mating, such as inbreeding or mate selection based on certain traits, can cause microevolution by altering allele frequencies in a population.
• 🧬 Mutations are a source of microevolution as they introduce new alleles that can change the gene pool's composition, such as the example of sickle cell anemia.
• 🌐 Gene flow, which includes the movement of individuals into or out of a population, can lead to changes in allele frequency and contribute to microevolution.
• 🌍 The script uses mitochondrial DNA as an example to illustrate how gene flow has shaped human populations and their allele frequencies across different geographical regions.
• 👍 Natural selection is a driving force of microevolution, where advantageous traits are selected for, leading to changes in allele frequency over time.
• 💊 Antibiotic resistance in bacteria is cited as an example of natural selection, where non-resistant bacteria are eliminated, and resistant ones pass on their genes.
• 🤝 The five main causes of microevolution are small sample size, non-random mating, mutation, gene flow, and natural selection, which can be remembered by associating them with the five fingers on a hand.

Q & A

What is the main topic of Mr. Andersen's podcast?

The main topic of Mr. Andersen's podcast is microevolution, which is the change in the allele frequency of a gene pool.

How does microevolution differ from macroevolution?

Microevolution refers to small-scale changes in allele frequency within a gene pool, whereas macroevolution involves large-scale changes over long periods of time, often leading to speciation.

What is the concept of a gene pool?

A gene pool is the complete set of all the genes in all the members of a population, which is shuffled through sexual reproduction to create new generations.

How does Mr. Andersen illustrate the concept of allele frequency?

Mr. Andersen uses the example of a small population with 10 individuals, half of whom have red hair due to having two genes for red hair, to explain allele frequency as the proportion of a particular allele in the gene pool.

What is the allele frequency for red hair in Mr. Andersen's example?

In the example, the allele frequency for red hair is 14 out of 20, or 0.7, assuming red hair is recessive.

What are the five factors that can cause microevolution, as mentioned in the podcast?

The five factors that can cause microevolution are small sample size, non-random mating, mutation, gene flow, and natural selection.

How does small sample size affect allele frequency?

Small sample size can lead to random changes in allele frequency due to the element of chance, as illustrated by the example of flipping a small number of coins versus a large number.

What is non-random mating and how can it cause microevolution?

Non-random mating occurs when individuals choose mates based on certain criteria, such as family ties or physical traits, which can lead to changes in allele frequency over time.

Can you provide an example of how mutation can cause microevolution?

A mutation that causes sickle cell anemia is an example where a change in the DNA sequence leads to a change in the hemoglobin protein, which can affect the allele frequency if the mutation provides a survival advantage in certain environments.

What is gene flow and how does it impact microevolution?

Gene flow refers to the movement of individuals or their genes into or out of a population, which can change the allele frequency by introducing new genetic variations or removing existing ones.

How does natural selection contribute to microevolution?

Natural selection contributes to microevolution by favoring individuals with certain traits that enhance survival and reproduction, thereby increasing the frequency of those traits' alleles in the gene pool.

Outlines

00:00

🧬 Microevolution and Gene Pool Dynamics

Mr. Andersen introduces the concept of microevolution, which is the change in allele frequency within a gene pool. He contrasts it with macroevolution, which involves large-scale changes over time leading to speciation. Using a small population example with red-haired individuals, he illustrates how the gene pool is shuffled through sexual reproduction, creating new generations. The essence of microevolution is the alteration of allele frequency, which can be measured and observed over generations. The video emphasizes five key factors that cause microevolution, hinting at a mnemonic device related to the human hand to remember them.

05:01

🔍 Causes of Microevolution: A Detailed Overview

This paragraph delves into the five main causes of microevolution. The first cause is small sample size, which leads to random genetic drift due to the chance variation in allele frequencies in small populations. The second is non-random mating, exemplified by historical cases of inbreeding and mate selection based on traits like eye color, which can lead to increased allele frequencies for certain characteristics. The third cause is mutation, where changes in DNA can result in new alleles, such as the mutation causing sickle cell anemia, which also conferred resistance to malaria. The fourth cause is gene flow, which involves the movement of individuals into or out of a population, altering allele frequencies and contributing to human diversity. Lastly, natural selection is the fifth cause, where environmental pressures favor certain traits, leading to their increased prevalence in the population, as demonstrated by antibiotic resistance in tuberculosis bacteria.

Keywords

💡Microevolution

Microevolution refers to small-scale changes in the allele frequency of a gene pool over a short period of time. It is a fundamental concept in the video, illustrating how genetic traits can evolve within a population. For example, Mr. Andersen discusses how a small population of 10 individuals with varying hair colors can exhibit changes in allele frequency, representing microevolution in action.

💡Macroevolution

Macroevolution is the large-scale evolutionary changes that occur over long periods, leading to speciation. It is contrasted with microevolution in the script, highlighting the difference in scale and time. Macroevolution involves significant genetic changes that result in the formation of new species, whereas microevolution deals with smaller, more immediate genetic shifts within a population.

💡Allele Frequency

Allele frequency is the proportion of a particular allele in a population's gene pool. It is a key measure in understanding genetic changes over time. In the script, Mr. Andersen uses the example of red hair, explaining that if 14 out of 20 alleles are for red hair, the allele frequency is 0.7. Changes in allele frequency are indicative of microevolution.

💡Gene Pool

The gene pool is the total set of all alleles in a population. It is the reservoir from which new generations are formed through sexual reproduction. The script describes how the gene pool is shuffled with each generation, akin to shuffling a deck of cards, which can lead to changes in allele frequency and thus microevolution.

💡Small Sample Size

Small sample size is one of the five factors that can cause microevolution, as mentioned in the script. It refers to the impact of random chance on the genetic makeup of a population when the number of individuals is small. This can lead to significant shifts in allele frequency, as seen in the script's example where the allele frequency drifts away from its original state due to random chance.

💡Non-random Mating

Non-random mating is another factor that can drive microevolution. It involves individuals choosing mates based on specific traits, leading to changes in allele frequency. The script provides examples such as inbreeding in royal families or mate selection based on eye color, both of which can result in increased prevalence of certain traits within a population.

💡Mutation

Mutation is a change in the DNA sequence that can introduce new alleles into a population. It is a critical factor in microevolution, as it can lead to the development of new traits. The script mentions sickle cell anemia as an example of a mutation that affects the hemoglobin protein, demonstrating how mutations can alter allele frequencies and contribute to evolutionary changes.

💡Gene Flow

Gene flow is the movement of genetic material from one population to another, either through migration or the introduction of new individuals. It is one of the factors that can cause microevolution, as it can significantly alter a population's gene pool. The script uses the example of human migration patterns, showing how gene flow can lead to different allele frequencies in different geographical regions.

💡Natural Selection

Natural selection is the process by which certain traits become more or less common in a population due to their impact on survival and reproduction. It is a major driver of microevolution, as it can lead to changes in allele frequency. The script illustrates this with the example of tuberculosis bacteria developing antibiotic resistance, showing how natural selection can favor certain alleles over others.

💡Inbreeding

Inbreeding is a form of non-random mating where closely related individuals reproduce. It is mentioned in the script as a way that can lead to microevolution, particularly in the context of royal families. Inbreeding can result in the concentration of certain genetic traits within a population, potentially leading to the development of unique characteristics or health issues.

💡Sickle Cell Anemia

Sickle cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene. It is used in the script as an example of how a mutation can lead to microevolution. Individuals with sickle cell anemia have a genetic advantage in areas where malaria is prevalent, demonstrating how mutations can influence allele frequencies and contribute to evolutionary processes.

Highlights

Microevolution is defined as a change in the allele frequency of a gene pool.

Macroevolution is contrasted with microevolution, referring to large scale changes over long periods leading to speciation.

A small population of 10 individuals with half having red hair is used as an example to illustrate gene pools.

Sex is described as a shuffling mechanism of the gene pool, creating new generations.

Allele frequency is calculated as the number of alleles for a trait divided by the total number of alleles.

Microevolution occurs with any change in allele frequency from one generation to the next.

There are five main causes of microevolution, symbolized by the five fingers on a hand.

Small sample size can lead to allele frequency changes due to random chance in small populations.

A computer simulation demonstrates allele frequency drift in populations of 20 versus 2000 individuals.

Non-random mating, symbolized by a ring finger, can cause microevolution, as seen in historical royal families.

Attraction to certain physical traits like blue eyes can lead to increased allele frequency for those traits.

Mutations, represented by the middle finger, are a source of microevolution, as they introduce new alleles.

Gene flow, indicated by the pointer finger, involves individuals moving in or out of a population, affecting allele frequency.

Natural selection, symbolized by the thumb, is the process where nature selects for survival based on traits.

The development of antibiotic resistance in tuberculosis bacteria is an example of natural selection.

A mnemonic using the hand is provided to remember the five causes of microevolution.

The importance of understanding allele frequency changes for the study of microevolution is emphasized.

Transcripts

Hi. It's Mr. Andersen and in this podcast I'm going to talk about microevolution which

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.