Introduction to Evolution and Natural Selection

Summary

This script delves into the misunderstood concept of evolution, clarifying that it's not a purposeful process but rather natural selection. It dispels the myth of organisms actively evolving to meet goals, using examples like the peppered moth and flu virus to illustrate how environmental pressures select advantageous traits over time, emphasizing the importance of this principle in understanding life's diversity.

Takeaways

• 🧬 Evolution is often misunderstood as a purposeful or active process, but it is actually driven by natural selection.
• 🦍 The common depiction of evolution as a progression from apes to humans is misleading; it suggests an active change rather than a passive process of natural selection.
• 🔄 Natural selection involves variation within a population, where environmental factors select for certain traits over others.
• 🦋 The peppered moth example illustrates how natural selection can lead to a change in a population's characteristics in response to environmental changes.
• 🌿 The Industrial Revolution's impact on the environment provided a clear example of how natural selection can favor certain traits, like the coloration of the peppered moth.
• 🐦 Predators play a significant role in natural selection by preferentially selecting prey with certain characteristics, affecting their survival and reproduction.
• 🤒 The flu virus is an example of natural selection in action, as it mutates and evolves to evade the human immune system.
• 💊 Antibiotic resistance in bacteria is a result of natural selection, where the overuse of antibiotics selects for bacteria that can survive their effects.
• 🛡 The immune system's response to pathogens like the flu virus is a form of natural selection, favoring the survival of those pathogens that can evade immune defenses.
• 🧬 DNA and genetic variation are at the core of natural selection, with random mutations leading to traits that may be advantageous in a given environment.
• 🌐 The concept of natural selection is fundamental to understanding life on Earth and could potentially apply to life on other planets, regardless of their biological makeup.

Q & A

What is the most misunderstood concept in science according to the speaker?

The most misunderstood concept in science, as per the speaker, is the idea of evolution.

Why does the common depiction of evolution in popular culture misrepresent the concept?

The common depiction misrepresents evolution by implying an active, intentional process, like an ape deciding to change its descendants' physical form, which is not how evolution works.

What is the correct term the speaker prefers to use instead of 'evolution'?

The speaker prefers to use the term 'natural selection' instead of 'evolution'.

What does the speaker mean by 'variation' in the context of natural selection?

Variation refers to the natural differences within a population of living organisms, such as differences in physical traits among individuals.

Can you explain the example of the peppered moth used in the script?

The peppered moth example illustrates how environmental changes can lead to natural selection favoring certain variations, like coloration that matches the environment for better camouflage.

How did the Industrial Revolution impact the color variation of the peppered moth?

The Industrial Revolution led to soot covering trees, changing their color to darker shades. This environmental change favored moths with darker coloration, which were less visible to predators, leading to a shift in the moth population's coloration.

What is the role of the immune system in the context of the flu virus and natural selection?

The immune system recognizes and attacks the flu virus. As it adapts to fight off the virus, natural selection favors virus strains that can evade the immune system's defenses, leading to the evolution of new flu strains.

Why does the misuse of antibiotics contribute to the development of antibiotic-resistant bacteria?

Misuse of antibiotics kills off susceptible bacteria, leaving behind those with random mutations that confer resistance. Without competition, these resistant bacteria can multiply, leading to the rise of 'superbugs'.

What is the significance of the flu virus example in demonstrating natural selection?

The flu virus example shows natural selection in real-time, as the virus mutates and evolves to avoid detection by the immune system, resulting in the emergence of new strains each flu season.

How does the speaker describe the process of natural selection in the context of bacteria and antibiotics?

The speaker describes it as a process where the use of antibiotics selects for bacteria that have random mutations making them resistant to the antibiotics, leading to the dominance of these resistant strains.

What is the broader implication of understanding natural selection for the study of life?

Understanding natural selection is fundamental to studying life because it is a universal process that can explain the diversity and adaptations of life forms across different environments and conditions.

Outlines

00:00

🧬 Misunderstandings of Evolution

The paragraph addresses the common misconceptions about the concept of evolution, which is often misunderstood as a process of change or improvement. It clarifies that evolution is not an active, goal-oriented process but rather a result of natural selection. The speaker uses the example of the popular but incorrect depiction of human evolution from apes, emphasizing that evolution is not about a creature's desire to change but about random genetic variations that may confer survival advantages over time.

05:01

🐛 The Peppered Moth and Natural Selection

This paragraph delves into the concept of natural selection using the example of the peppered moth in England during the Industrial Revolution. It explains how the moth's coloration, which varied naturally in the population, became a significant factor for survival as the environment darkened due to soot. The darker moths, which were better camouflaged against the soot-covered trees, were less likely to be eaten by birds, thus increasing their chances of reproduction. Over time, this led to a predominance of darker moths in the population, illustrating natural selection in action without any conscious effort by the moths themselves.

10:02

🤒 The Influenza Virus and Annual Evolution

The speaker discusses the annual evolution of the influenza virus as a real-time example of natural selection. The immune system's ability to recognize and attack the virus puts pressure on the virus to mutate and change its surface proteins to evade detection. This results in the emergence of new strains of the flu virus each year, which are better at infecting hosts whose immune systems are adapted to previous strains. The paragraph highlights the dynamic nature of evolution and how it can be observed within a single human lifetime.

15:02

🛡️ Antibiotic Resistance in Bacteria

The final paragraph explores how the misuse of antibiotics can lead to the selection of antibiotic-resistant bacteria, often referred to as superbugs. It explains that in a population of bacteria, random mutations can create variations that may confer resistance to antibiotics. When antibiotics are used excessively, they kill off susceptible bacteria, leaving the resistant strains to multiply unchecked. Over time, this can lead to the dominance of resistant strains, rendering the antibiotics ineffective. The paragraph emphasizes the importance of understanding natural selection to appreciate the complexity of living systems and the potential consequences of human actions on evolution.

Keywords

💡Evolution

Evolution is a fundamental concept in biology referring to the change in heritable characteristics of biological populations over successive generations. In the video, the term is discussed as often misunderstood and misrepresented, especially in popular culture. The script clarifies that evolution is not an active, goal-oriented process but rather a natural outcome of random genetic variations being selected for or against by environmental pressures.

💡Natural Selection

Natural selection is the process by which certain heritable traits become more or less common in a population due to their effect on the survival and reproduction of individuals. The video emphasizes that natural selection, not evolution itself, is the mechanism driving change in species over time. It is illustrated through examples like the peppered moth and the flu virus, showing how environmental changes can select for traits that confer a survival advantage.

💡Variation

Variation refers to the differences in traits among individuals within a population. The script explains that variation is a key component of natural selection, as it provides the raw material for environmental factors to select from. Examples given include the variations in the peppered moth's coloration before and after the Industrial Revolution, which affected their survival rate due to predation.

💡Peppered Moth

The peppered moth is used in the script as a classic example of natural selection in action. It illustrates how a change in the environment (pollution from the Industrial Revolution) led to a change in the frequency of a particular trait (coloration) within the moth population, as the darker moths were less visible to predators against the soot-darkened trees.

💡Mutation

A mutation is a change in the DNA sequence that makes up a genome. In the context of the video, mutations are random changes that can introduce new variations into a population. The script mentions mutations in the flu virus as a way to explain how natural selection can lead to the emergence of new strains that are resistant to the human immune system's defenses.

💡Flu Virus

The flu virus is highlighted in the script as an example of rapid evolution through natural selection. The virus mutates frequently, leading to slight variations in its surface proteins. When the human immune system adapts to recognize and attack the predominant strain, a mutated strain with a different protein pattern may have a survival advantage, becoming the dominant flu virus of the next season.

💡Antibiotic Resistance

Antibiotic resistance is the ability of bacteria to withstand the effects of antibiotics, which is a significant public health concern. The script discusses how the overuse of antibiotics can lead to the selection of resistant bacteria. It explains that by killing off susceptible bacteria, the remaining resistant strains can multiply without competition, eventually becoming the dominant type in the population.

💡Bacteria

Bacteria are single-celled microorganisms that can cause infections. In the video, bacteria are used to explain the concept of antibiotic resistance. The script points out that random mutations in bacteria can lead to some individuals being unaffected by antibiotics, and when these are the only ones left to reproduce, they pass on their resistance to future generations.

💡Superbug

A superbug is a term used to describe bacteria that have become resistant to multiple antibiotics, making infections they cause difficult to treat. The script uses the term to illustrate the potential consequence of natural selection when antibiotics are used excessively, allowing resistant bacteria to thrive and dominate.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. The script briefly mentions DNA in the context of mutations and its role in heredity, which is central to the process of evolution and natural selection.

Highlights

Evolution is a misunderstood concept, often associated with the idea of change and progress, but not an active or intentional process.

The common misconception is that evolution is a linear process from apes to humans, implying an 'upright' posture is superior.

Evolution is not about an organism's desire or intent to change, but rather a natural process without active direction.

The concept of 'natural selection' is preferred, emphasizing the role of environmental factors in selecting for certain traits.

Variation within a population is key to natural selection; it's the basis for environmental factors to select certain traits over others.

The peppered moth example illustrates how industrial pollution selected for moths with darker coloration, making them less visible to predators.

Natural selection does not imply design or intent by the organisms; it's a result of random variation and environmental pressures.

The flu virus demonstrates natural selection in real time, as it mutates to evade the human immune system.

Antibiotic resistance in bacteria is a modern example of natural selection, where misuse of antibiotics selects for resistant strains.

The development of 'superbugs' is a consequence of natural selection, not a designed response by the bacteria.

Evolution and natural selection are observable in real-time processes, contrary to the belief that they only occur over vast periods.

The concept of natural selection is fundamental to understanding living systems and can be applied universally, even in hypothetical extraterrestrial biology.

Biology, at its core, relies on the understanding of natural selection, which is essential even in the absence of other familiar biological concepts.

The transcript emphasizes the importance of distinguishing between the everyday misconceptions and the scientific reality of evolution.

The lecture aims to clarify the scientific concept of evolution and dispel myths surrounding its process and implications.

Natural selection is presented as a powerful and observable mechanism that shapes the diversity of life on Earth.

Transcripts

I think what is probably the most misunderstood concept in

all of science, and as we all know is now turning into one

of the most contentious concepts, maybe not in

science, but in our popular culture, and that's the idea

of evolution.

Whenever we hear this word, I mean, even if we don't hear it

in the biological context, we imagine that something is

changing, it is evolving.

And so when people use the word evolution in our everyday

context, they think of this notion of change, that-- this

is going to test my drawing ability-- but you

see an ape bent over.

We've all seen this picture at the natural museum, and he's

walking hunchback like that, and his head's bent down and--

oh, I'm doing my best. That's the ape.

Maybe he's also wearing a hat.

And then they show this picture where he slowly,

slowly becomes more and more upright, and eventually, he

turns into some dude, who's just walking on his way to

work, also just as happy, and now he's

walking completely upright.

And it's some kind of implication that walking

upright is better than not walking upright,

et cetera, et cetera.

Oh, he doesn't have a tail anymore.

Let me eliminate that.

This guy does have a tail.

Let me do it in an appropriate width.

This guy has a tail, so you're going to have to excuse my

drawings skills, but we've all seen this.

If you've ever gone to a natural history museum, and

they'll just make more and more upright apes, and

eventually you get to a human being, and it's this idea that

the apes somehow changed into a human being.

And I've seen this in multiple contexts, even inside of

biology classes and even the scientific community.

They'll say, oh, the ape evolved into the human or the

ape evolved into the pre-human, the guy that almost

stood upright, the guy that was a little bit hunchback, so

he looked a little bit like an ape and a little bit like a

human and so on and so forth.

And I want to be very clear here.

Even though this process did happen, that you did have

creatures that over time accumulated changes that maybe

their ancestors might have looked more like this, and

eventually they looked more like this, there was no active

process going on called evolution.

It's not like the ape said, gee, I would like my kids to

look more like this dude, so somehow, I'm going to get my

DNA to get enough changes to look more like this.

And it's not like the DNA knew.

The DNA didn't say, hey, it is better to be walking than to

be kind of hunchbacked like an ape.

And so therefore, I'm going to try to somehow spontaneously

change into this dude.

That's not what evolution is.

It's not like-- you know, some people imagine that maybe

there was a tree.

There's a tree, and on that tree, there's a bunch of good

fruit at the top of the tree.

Maybe they're apples.

And then maybe you have some type of cow-like creature, or

maybe it's some type of horse-like creature that says,

gee, I would like to get to those apples, and that just

because they want to get there, maybe the next

generation-- they keep trying to raise their neck, and then

after generation after generation, their necks get

longer and longer, and eventually

they turn into giraffes.

That is not what evolution is and that's not what it

implies, although sometimes the everyday notion of the

word seems to make us think that way.

What evolution is-- and actually, this is the word

that I prefer to use-- it's natural selection.

Let me write that word down.

Natural selection.

And literally, what it means is that in any population of

living organisms, you're going to have some variation, and

this is an important keyword here.

Variation just means, look, there's just some change.

If you look at the kids in your

school, you'll see variation.

Some people are tall, some people are short, some people

have blond hair, some people have black hair,

so on and so forth.

There's always variation.

And what natural selection is is this process that sometimes

environmental factors will select for certain variation.

Some variations might not matter at all, but some

variations matter a lot.

One example that's given in every biology book, but it

really is interesting is-- I believe they're called the

peppered moth.

And this was in pre-Industrial Revolution England that these

moths-- some of the moths were-- let me see if I can

draw a moth.

I think you get the idea.

Let me draw a couple of them.

Let me draw a few peppered moths.

A couple of peppered moths there.

Let me draw one more.

So most peppered moths, there was just this variation.

Some of them were-- I guess we could call them more peppered

than others.

So some of them might look like this.

You know, they had-- let me do other colors.

Let me do a white.

So it had spots like that.

Some of them might have looked more like that.

And, of course, they had some black spots on them.

And then some of them might have been-- just

barely have any spots.

You just have this natural variation.

Like you'd see in any population of animals, you'll

see some variation in colors.

Now, they were all happy, probably for thousands of

years, just this natural variation.

It was a non-important trait for these peppered moths.

But then, all of a sudden, the Industrial Revolution happens

in England, and all this soot gets released from all of

these factories that are running these steam engines

powered by coal.

And so, all of a sudden, a lot of the things that once were

grey or white, for example, maybe some tree trunks.

Let me draw some tree trunks.

Maybe there were some tree trunks that used

to look like this.

You know, maybe it looked like a-- maybe it kept a-- maybe

some tree trunks used to look something like this, and a

peppered moth would be pretty OK.

Maybe there are some tree trunks that were pretty dark.

But all of a sudden, the Industrial Revolution happens.

Everything gets covered with soot from the coal being

burned, and then all of a sudden, all the

trees look like this.

They're just completely pitch black or they're a lot darker

than they were before.

Now, all of a sudden, you've had a major change to these

moths' environment, and you have to think what is going to

select for these moths?

Well, one thing that might get these moths are birds and the

ability of the birds to see the moths.

So all of a sudden, if the environment became a lot

blacker than it was before, you can guess

what's going to happen.

The birds are going to see this dude a lot easier than

they're going to see this dude, because this dude on a

black background, he's going to be a lot harder to see.

And it's not like the birds won't catch this guy.

They'll catch all of them, but they're going to catch this

guy a lot more frequently.

So you can imagine what happens.

If the birds start catching these guys before they can

reproduce, or maybe while they're reproducing, what's

going to happen?

This guy, the darker dudes, are going to reproduce a lot

more often, and all of a sudden, you're going to have a

lot more moths that look like this.

You're going to have a lot more of these dudes.

So what happened here?

Was there any design or was there any active change by any

of the moths?

Did any of the moths-- I mean, it looks like a really smart

thing to do to become black, right?

Your surroundings became black, and you wait a couple

of generations of these moths, and now all of a sudden, the

moths are black.

And you might say, wow, those moths are geniuses.

They all somehow decided to evolve into black moths in

order to hide from the birds more easily.

But that's not what happened.

You had a lot of variation in your peppered moth population.

And what happened was that when everything turned darker

and darker, these dudes right here-- and dudettes-- had a

lot less success in reproducing.

These guys just reproduced more and more and more, and

these guys got eaten up before they were able to reproduce or

maybe while they were reproducing so that they

couldn't produce as many offspring, and then this trait

just became dominant.

And then the peppered moth just became-- you can kind of

view it as a black moth.

Now, you might say, OK, Sal.

That's one example.

I need more.

This is natural selection.

It's purported to apply to everything.

It purports to explain why we evolved from basic bacteria or

maybe even self-replicating RNA, which I will talk about

more in the future.

I need more evidence of this.

I need to see it in real time.

And the best example of this is really the flu.

And I'll do other videos in the future on what viruses are

and how they replicate.

Viruses are actually fascinating, because it's not

even clear that they're alive.

They're literally just little buckets of DNA and sometimes

RNA, which we'll learn is genetic information, and

they're just contained in these little protein

containers that are these neat geometrical shapes, and that's

all they are.

They're not like regular living organisms that actively

move and that actively have metabolisms and all that.

What they do is they take that little DNA, and they inject it

into other things that can process it, and then they use

that DNA to produce more viruses.

But anyway, we can do a whole series of videos on viruses,

but the flu is a virus.

And what happens every year is you have a certain type a

virus, and they have some variation.

I'll just make the variation by how many dots they have.

And they infect-- let's say it's a human flu.

They infect humans, and slowly our immune systems, which we

can make a whole set of videos on as well, start to recognize

the virus and are able to attack them before they can do

a lot of damage.

So now you can imagine what happens if, let's say, that

this is the current flu.

Let me do all of them.

They all have these little two dots and that's how-- and

we'll talk in the future what these dots are and how they

can be recognized.

But let's say that's how our immune system recognizes them.

They start realizing, oh, any time I get this little green

dude with two dots on it's, that's not a good thing to

have around so I'm going to attack it in some way and

destroy it before he infects my DNA and all the rest. And

so you have a very strong natural selection once immune

systems learn what this virus is-- and we'll talk more about

what learning means for an immune system-- that they'll

start attacking these guys, right?

But flu, you can kind of think of them as being tricky, but

they're not really tricky.

They're not sentient objects, but what they do do is they

constantly change.

So what you have is, in any flu population, you're always

having a little bit of change.

So maybe the great majority of them have those two dots, but

maybe every now and then, one of them has one dot, one of

them has three dots, and maybe that's just a random mutation.

This just randomly happened.

Maybe this is one in every-- I'll make up a number: One in

every million of these viruses have this only one dot instead

of two dots.

But what's going to happen as soon as the human immune

system gets used to attacking the virus

with the two red dots?

Well, then this guy isn't going to have to compete with

the other virus capsules for infecting people.

He's going to have people's DNA all to himself.

And so he or she, or whatever you want to call this virus,

is then going to be more successful.

So by next year's flu season when people start sneezing and

are able to spread it on doorknobs and whatever else

again, this guy's going to be the new flu virus.

So when you see this process of every year there's a new

flu virus, that is evolution and natural

selection in real time.

It is happening.

It isn't this thing that only happens over eons and eons of

time, although most of the kind of the substantial things

that we see in our lives or even ourselves are based on

these things that happened over eons and eons of time,

but it happens on a yearly basis.

Another example is if you think about

antibiotics and bacteria.

Bacteria are these little cells that move around, and

we'll talk more about them.

They actually are definitely living.

They have metabolisms and whatever else.

And this is just a nice note.

When people talk about infections, it could either be

a viral infection, which are these things that go and

infect your DNA and then use your cell mechanisms to

reproduce, or it could be a bacterial infection, which are

literally little cells that move around and they release

toxins that make you sick and whatever else.

So bacteria, these are what antibiotics kill.

Actually, I don't think there's a hyphen.

They attack bacteria.

They kill them.

If you know a couple of doctors or whatever and you

say, hey, I'm sick.

I think I have a bacterial infection.

Give me some antibiotics.

A responsible doctor says no, I won't give you antibiotics

just willy-nilly, because what happens is, the more

antibiotics you use, you're more likely to create

versions-- and I want to be very careful about the word

create, because you're not actively creating them.

But let's say-- and let me finish my sentence.

You're very likely to help select for

antibiotic-resistant bacterias.

Now, how does that work?

Let's say that these are all bacteria and you have

gazillions of them, right?

Every now and then, you get one that's

slightly different, right?

Now in a population of bacteria, these all will make

you equally sick, and this is just some random difference in

the bacteria.

Maybe on its DNA some slight different changes happened,

but whatever happened, these all are a kind of bacteria.

You don't want to get a lot of them in your system.

Your immune system can attack them and fight them off, but

if you get a lot of them, then they might kill you or make

you sick or whatever else.

Now, if everyone just starts using antibiotics when they're

not sick or when they don't really need to in a

life-or-death situation, you might have an antibiotic that

is really good at killing the green bacteria.

But what happens if you all of a sudden kill a

lot the green bacteria?

Well, now the blue bacteria have the whole ecosystem that

before it was competing with all these green dudes to get

at all the good stuff inside of your body, but now he's all

alone, and now he can replicate willy-nilly.

So now he's going to replicate willy-nilly, and obviously--

once again, it wasn't like there was any design, there

was any intelligent process here that said look, this

bacteria should-- some bacteria said, oh, I'm going

to be little bit smarter and design myself to resist this

antibiotic threat.

No!

There's just these random changes that happen, and

mutations and viruses and bacteria happen frequently and

these random changes that happen, and this might be a

one in one billion change, right?

But all of a sudden, if you start killing off all of the

people it's competing with, this guy can start replicating

really fast and then become the dominant bacteria.

And then all of a sudden, that antibiotic that you had

developed very carefully to destroy the green dudes is

useless, and you have this superbug.

You might have heard the word superbug.

That's what a superbug is.

It's not like it designed itself somehow.

It's just that we got very good at killing its

competition, and so we allowed it to take over, and we can't

kill it, because all of the drugs were just good at

killing its competition.

These bacteria just keep mutating and keep mutating,

and if we use these antibiotics a little bit too

heavily, we'll always be selecting for the things that

won't be affected by the antibiotics.

Well, anyway, I think I've spoken long enough, but this

is a fascinating, fascinating topic.

And I really wanted to make this my very first video or

lecture if you will, on biology, because if you really

went to-- you know, biology is the study of life, and we can

talk about what life is, whether

viruses are living, whatnot.

But if you really want to study living systems, you

really can't make any assumptions other

than natural selection.

We could go to another planet where the creatures don't have

DNA, or maybe they have some other type of hereditary

information stored in their cells, or they replicate some

other way, or they're not even carbon based.

Maybe they're silicon based.

And if we went to that type of a planet in order study the

biology on that planet, everything else we know about

biology, about viruses and DNA, would be useless.

But if we do understand this one concept, this one concept

of natural selection, that your environment will select,

and it's not-- you know, there's no

active process here.

It's just random stuff happened and they randomly

select for random changes.

And over large swaths of time, and these are unimaginably

large swaths of time, those changes essentially

accumulate, and they might accumulate into fairly, fairly

significant things.

We'll talk more about this in another video.

See you soon.