Natural Selection

Natural Selection


Hello. It’s Mr. Andersen and
welcome to Biology Essentials – video 1. This is on natural selection so I’ve included a
picture here of Charles Darwin. Most people think that Charles Darwin is famous because
he somehow invented evolution. That’s not totally accurate. Why Charles Darwin is famous
is that he’s the first scientist that really gave us the mechanism that explains how evolution,
especially adaptation can occur. And so if you are trying to learn biology the best place
to start is with Charles Darwin and a better understanding of natural selection. Before
we can talk about natural selection, however, we should define what evolution is. And so
in this class in evolution, evolution is simply going to be changes, biological evolution
is any changes to the gene pool. So a gene pool is a combination of all the genes in
a population or we call those different varieties alleles in a population. And so according
to scientists the gene pool should remain at equilibrium. In other words, the frequency
of the different alleles will never change unless you violate one of these five constraints
of Hardy-Weinberg Equilibrium. And it happens all the time, so evolution is constantly occurring
and it can occur if you have a small population, non-random mating, mutations, migration. So
these five things can cause evolution but we are going to talk about those later. Today
I want to talk about selection. Because selection is when you live or die, it’s called differential
reproduction success, when you live or die based on the appearance that you have. In
other words you’re made the way you are and as the environment changes you’re selected.
Either you have high fitness and you’re able to survive and pass your genes on or you have
low fitness and you die. And if you have enough fitness over time, that can eventually lead
to adaptions in a population. So the smallest unit that can actually evolve is a population
and it’s simply changes in the gene pool. Why do we start with natural selection? Well
of these five things here, it’s the only one that can lead to adaptation or organisms that
are better adapted to their environment. And so let me give you an example of that. Let’s
say you have a bacterial infection. Let’s say you are infected by a number of bacteria,
let’s call them seven and you decide to treat the bacteria. So let’s say you take some antibiotics,
penicillin for example. And they have different varieties of resistance to that antibiotic.
And so when you take the antibiotic on day one it destroys or lysis or pops all of these
bacteria, those that have low resistance. So these ones are selected, in other words
the ones that have a high resistance are selected for. The ones that have a low resistance are
actually going to die. These ones then will reproduce through binary fission and we’re
going to have a new population of organisms that have a better resistance to antibiotics.
Now there are two ways that we can actually get variety in a population. The only was
we can get new novel characteristics in other words like the ability to be resistant to
antibiotics is through mutation. Everything that’s been added to the first strand of DNA
in that first living thing has been added through a mistake or a change in the DNA and
that’s called a mutation. The other thing that can actually create variety is reproduction.
And so in bacteria they use asexual reproduction but they have mechanisms by which they can
change those mutations or vary those mutations or pass them on. In us its just sex and sex
is going to take those mutations and then in our offspring create a variety of different
types. And so this is just theoretically how natural selection occurs. But let me give
you maybe the most famous example of how natural selection occurs in the wild. And right here
is a picture of a peppered moth. A peppered moth has two different varieties, it has the
dark phenotype or physical characteristic and the light phenotype. Now we know this
about moths, that the light phenotype is actually homozygous recessive (dd). In other words
that is a recessive trait. And the dark appearance you can be either homozygous dominant (DD)
or you can be heterozygous dominant (Dd) for that and you’re going to have the dark appearance.
And so if you look at this wood right here where it appears today you can see that this
one, the light phenotype or the light physical characteristic is camouflaged. In other words
it fits in. If you are a bird flying over and you are looking for moths to eat you’re
not going to see that light appearance. You’re going to see that dark appearance and you
are going to go eat that moth. And so you are going to select that dark appearance.
You are going to kill that dark appearance and its genes are going to die with it. And
so at this point the light moth is going to have a higher fitness. It’s more likely to
survive, reproduce and pass its genes on generation after generation. So natural selection has
created this appearance. Now why would we even have the dark moth. Well maybe they can
fit in on some of these dark splotches or maybe they can help them and that’s actually
what happened. And so in the Industrial Revolution in the 1800s coal powered plants started to
push coal dust out into the environment and so the environment started to get darker.
In other words as that coal dust started to accumulate on the trees the trees got darker
and darker and darker. When they got darker these moths that were light in appearance,
now they started to pop out and those are the ones that were going to be preyed on by
the birds themselves. And so what happened was a change in the gene pool and natural
selection or evolution occurred. So let’s look at some actual numbers. In 1848, 98%
of the individuals were light in appearance and only 2% were the dark. And so we an actually
figure out what the gene pool frequencies were. And so over here I have 100 genes and
all of them are light right now. So let’s figure out how many of them were light. And
so right here to understand this you have to have an understanding of Hardy-Weinberg
equilibrium. And so here’s our famous equation. If you don’t know this you should probably
look at the video on Hardy-Weinberg Equilibrium. P squared stands for the individuals that
are homozygous dominant. 2pq stands for the individuals that are heterozygous and q squared
tells us what individuals are, the frequency of the individuals that are homozygous recessive.
And so we can actually use this whenever we are doing these problems. We usually start
with the recessive and we can figure out the allele frequency. And so 98% of the individuals
we know that they are little d little d. That they’re light in appearance. And so I can
set q squared equal to 0.98. I can take the square root of both of those, and I’ve done
this earlier so I know that q is roughly .99. In other words q tells us the allele frequency.
And so that means that back in the day, in 1848, 99 out of 100 were of the light allele
frequency and only 1 out 100 were of the dark frequency. And so that’s a simple Hardy Weinberg
problem. Now let’s see what happens over the next fifty years. Well if we check back in
the next 50 years we find that the population has changed quite a bit or it has evolved
quite a bit. And so it’s almost reverse. So now we have 5% of those that are the light
appearance because they are being prey on birds. And 95% of those are on the dark appearance.
Let’s see what happened to the actual allele frequency. And so we know that q squared at
this point is not 0.98 it is .05. And so if I take the square root of that, q now equals
roughly 0.22. In other words the gene pool has changed. The gene pool has changed dramatically.
We used to have 99% or 0.99 as our q value but now it is only 0.22. And so we still have
a lot of those dark around. We still have a lot of those light around but it’s changed
over time. And the reason it’s changed over time is due to selection. In other words the
environment changed and when the environment changed then they adapted, or the population
adapted. What can that lead to? Well it eventually can lead to something called an adaptation.
So an adaptation, if we talk about an adaptation, is the best example or the best word for that
is a process. We tend to think lots of times that an adaptation has to be a physical characteristic,
but it could be your behavior that you have. And so what is an adaptation? It is a process
that is selected for. In other words let me give you an example of that. In the Rift Valley,
it is a great place to study evolution right now, in the Rift Valley we have these lakes
and the lakes are inhabited by a type of fish called a cichlid. What’s unique about a cichlid
is that they have this jaw out here that we can see. It’s not quite that big, but the
have another jaw back here. It’s called a pharyngeal jaw. And what that allows them
to do is to use that for different processes for feeding, for feeding on different foods
and by doing that they are able to, they are able to exploit a number of different niches
in that environment. And so what we have seen is an explosion of cichlid populations in
these lakes in Africa. It started with just probablyone or a few different types of cichlids
and they have adapted to fill all of these different roles. And so they’re perfectly
adapted for that environment. How did they become perfectly adapted? It’s just through
a process of natural selection. As that environment starts to change, and they are starting to
change, as we get invasive species or fish that weren’t there to begin with, then we’re
going to have pressure, change in the environment and those species are going to have to adapt.
And so this is how we get species. It’s just evolution taken to its extreme where we get
macro evolution or big changes so species can’t interbreed anymore. And so that’s a
lot, but we’re just getting started. And so what’s natural selection? Natural selection,
if I could give you one example, the best definition for what natural selection is,
natural selection is simply differential reproductive success. In other words, we’re each made a
little bit different. If that allows us to survive and pass those genes on, we have high
fitness, that eventually can lead to adaptations. But again there’s no goal towards this perfection.
It’s simply random changes that are selected by the environment. And that’s why Charles
Darwin is famous. So thanks.

100 thoughts on “Natural Selection

  1. I am unsure about the mutations. This seems to all depend on mutations, which are apparently somewhat random. I'll check and see if there is also a video that explains the mutations in more detail. Meanwhile, if anyone can shed some light on this for me. I am asking out of curiosity only. So the replied don't have to be geared to studying or testing. I just want to know.

  2. So good of you to do this, even after having to re-do so much of your work. It is unfortunate that the publisher didn't want to share any images. Students and schools still have to buy textbooks, so these videos that include a few of their images are no likely to compete with them. Perhaps the publishers could make great videos, and put them online with ads so they still profit from their product. Anyway, thanks for all the videos.

  3. 'wait, daddy…i dont get it…. if… if… *innocence* if the birdies play nice with the moths…what happens to all dem little white moths? Do they go visit the same farm that sparky and grampa Joe went to?'
    'uhm…yeah…'

  4. Thank you very much. I wish all teachers were like you. I never understood natural selection in high school and now in in my 3rd year in college and just now, I know what it is thanks to you. God bless you

  5. Im in Australia and all of this (and more) is taught in first – second level University. Is this what American Senior students in High School learn?

  6. Basically, but we do go further into it in university. Still, the basics like this I remember learning in biology, but not to this depth. That could be my science teachers fault. Good news for you is that you will still be learning or re-learning this in university 🙂

  7. Also, the curriculum for biology I think, is a little different in each state. I did high school (op) biology in qld then moved to vic for uni (doing first year bio) and the things I learned/did are different to vce bio here. But you're right, uni does go into more details than high school.

  8. But genes (i.e. micro) are instructions for how animals grow (i.e. macro). Genetic mutation can arise a variety of ways including Gene Duplication and copying errors, damage to existing DNA, inherited mutation. Genes can also become dormant or active. But Gene Duplication, for example, demonstrates that new genes (new information) is created through mutation.

  9. how can the fuck anyone take this shit , what the fuck is wrong with you poeple , we have more then a fucking 100 bilion kilometre of dna on our body , it almost 300 time to go to the sun and back of information , just to make you , can't you see that we are double , , we have 2 eyes ,2 ears 2 of 5 fingers , 2 legs , you know what is mutation ,is the fucking information get lost or changed (we have to have iformations to get the mutation) you know what is 100 bilion kilomitr of dna ,it must have a fucking 500000 of good mutation per year for evryeone of this living spiecies to apear in this period of time , and it have to hapen in double , beceaus your 2 eyes eash have it's own dna , do you know what is the chance to have only 1 good mutation it 10^120 , do you know what it means , it means impossibul just for one mutation , and you are talking to me about a firefly , this firefly didn't came with new information , it's call mixing , how the fuck can a random processe give you a 150 migapixl camera , and twice , the good mutation to make you survive , go and shave your eyebrows and see if it's gonna kill you or efect your life , i know girls that don't have a hear there , and you knwo what is the fonction of theme , it's that big , and can't you see that a fucking amazing machin ,this is like to see that someone is realy believe that this univers is only 6000 year old 

  10. achraf844 nobody cares what u think keep it to ur self. Its funny cause u spent time  in ur life writng like 20 comments after saying this sucks.

  11. Evolution has no "proof," because it's a fraud. And the atheist/evolutionist philosophy is LESS than worthless. What does the atheist/evolutionist have to crow about? NOTHING! They have nothing to offer society or self whatsoever, because their philosophy claims they are an evolved animal living a meaningless "non-purpose life" – headed to a meaningless and worthless "dead end" grave RAPIDLY forgotten.

    Anybody can see the atheist/evolutionist philosophy offers people nothing but dung. Dung for their past, dung for their current life and nothing but dung for their future. The Bible describes the philosophy of atheism/evolution here: “The fool hath said in his heart, there is no God.” – Psalms 53:1

    I’m here to set the lost free. You must realize the “good news” that Jesus loves you…I must ask you, "what else SHOULD God do to "show" himself to you? Because it's not "faith" on your part for him to personally appear to you and do a few miracles. Surely you've heard "The Gospel" by this time in your life? Did you not hear it? And apparently, you made the decision to reject the gospel. Because without a savior to save you from the sin curse you received from Adam, you're end will be far beyond sad. I hope anyone that is lost reads this and changes their mind.

    By the way, I'm a retired 53 yr old happily married Doctor that's loved the Lord for 40 yrs.

  12. Be careful with the use of Hardy-Weinberg when a population is under selection!  The equation is ONLY USEFUL when the population is actually AT EQUILIBRIUM (not so in the example of the peppered moths).  Thus, the calculation of allele frequencies by taking the square root of the homozygous recessive frequency is wrong.

  13. Natural selection works. But there is no proof for entirely new species. Evolution is more or less bunk.

  14. Biologists define evolution as descent with modification and it's the foundation of modern biology. Natural selection is one of the mechanisms of biological evolution, along with mutation, migration, and genetic drift. It's more than a hypothesis, because it's been tested and confirmed millions of times. It's a scientific theory, meaning an explanation of evidence, as well as a fact of biology.

  15. Thank you so much for making these videos!!!!! They are so helpful and you can truly see the results on the AP!!! Your videos saved me right before the test and I am literally recommending them to everyone I know! Thanks again!!!!!!!!!!

  16. evolution by natural selection is not only valid for the differentiation  of species,, but also for other fields, like economy and technology. for example, capitalism will be replaced sooner or later by other more adaptable economy…

  17. So natural selection is pretty much "Fight or Flight"?
    But why would I want to fight when I can fly?
    And if I chose to fight, what if I win?
    Is there a positive in either situation, therefore Natural Selection is almost meaningless?
    Do I sound intelligent, when I'm the one asking the questions?
    I'm actually just rambling. Fight me.

  18. 'Intelligent design' teaching BANNED – A court in the US has ruled against the teaching of "intelligent design" alongside Darwin's theory of evolution. A group of parents in the Pennsylvania town of Dover had taken the school board to court for demanding biology classes not teach evolution as fact. The authorities wanted to introduce the idea that Earth's life was too complicated to have evolved on its own. Judge John Jones ruled the school board had violated the constitutional ban on teaching religion in public schools.
    The 11 parents who brought the case argued that teaching intelligent design (ID) was effectively teaching creationism, which is banned. The separation of church and state is enshrined in the US constitution. The school board argued they had sought to improve science education by exposing pupils to alternatives to Charles Darwin's theory of evolution. But Judge Jones said he had determined that ID was not science and "cannot uncouple itself from its creationist, and thus religious, antecedents". In a 139-page written ruling, the judge said: "Our conclusion today is that it is unconstitutional to teach ID as an alternative to evolution in a public school science classroom." He accused school board members of disguising their true motives for introducing the ID policy.
    "We find that the secular purposes claimed by the board amount to a pretext for the board's real purpose, which was to promote religion in the public school classroom," he said.
    He banned any future implementation of the policy in Dover schools. The case, the first of its kind, sets an important precedent in a country where several states have adopted the teaching of ID, reports the BBC's James Coomerasamy in Washington.
    Ironically, he adds, it is a somewhat academic ruling in the Dover area since parents there voted last month to replace the school board members who brought in the policy.
    That move provoked US TV evangelist Pat Robertson to warn the town was invoking the wrath of God.
    A lawyer for the parents said the ruling was a "real vindication" for those families who challenged the school board.
    Judge John Jones: "We find that the secular purposes claimed by the board amount to a pretext for the board's real purpose, which was to promote religion". Source: "BBC NEWS"

  19. My teacher is obsessed with you. He kinda copies your appearance and all he does to teach us most of the time is have us watch your videos ._.

  20. This is all very fascinating, but I have a question. I do agree evolution is occurring… just in case someone thought I wasn't.

    Onto the question then. What would happen to the population of moths if there's only homozygous dominant or homozygous recessive alleles left in the gene pool? I mean, these species have been able to evolve because none of the alleles dissappeared and that's quite plain to see. The allele was reduced to a very small percentage yes, but it didn't completely dissappear. So my question is, if one only has purebreds in a given population, and if they only produce offspring with the same allele from generation to generation, what would happen when the environment is fully and completely changed in favour of the lost allele? How will the lost allele be regained through mutation and natural selection if mutations are random mistakes that occur during meiosis or mitosis? Also, what's the point if all sorts of mutations occur, except the one that we actually want? Wouldn't that be more detrimental to the organism? Has such an experiment been conducted yet? Because I'm extremely curious to know these things…

  21. "Either you have high fitness and you're able to survive and pass your genes on…. or you have low fitness and you die"
    WHAT A SAVAGE

  22. The example of the moth obviously shows how something might survive, but not how it arrived in the first place. It started with moths and ended with moths, nothing new was formed.

  23. Just want to leave a huge thank you. I attribute the 5 I got on the Biology AP exam solely to these videos. I watched them through taking notes, then again two more times. Studied the material in the videos and then took some practice tests. What I learned in highschool biology AP focused heavily on the body systems which were not highlighted during the AP test, and pretty much nothing else. Honestly these videos are the best resource out there for the AP exam. Can't say thank you enough.

  24. Pepper moth is a fraud. They don't even live on trucks and only active at night, when color and birds are not relevant. They glued them to this trunk. This is science?

  25. There had always been dark and light Peppered Moths before the Industrial Revolution. Let's see, the dark moths are still he same species as the light moths, just like black and white dogs are both the same species. So, .really, they are an example of evolution NOT happening! Or if that is not true, what are they "evolving" into that is not a moth? And btw even if the dark Peppered Moths had turned into a different species, that would still not support evolutionism.
    .
    We are told over and over and over that a new species shows evolution. Nope. Speciation (the creation of new species) does not support evolution as it is an example of stasis and stasis is the exact opposite of evolution. For ex. over 200,000 species of beetles are all still beetles. There are thousands upon thousands of species of birds, bees, lizards, trees, bacteria, trees, yeast, flowers, whatever. If a new species develops within any groups at all, you can bet your bottom science dollar that it will still be just a beetle, bee, bacteria, tree, fish, or whatever.
    .
    We are supposed to fill in the blanks here with…faith…and think, "Well! If a new species develops then things just keep evolving and evolving from there on." But the next step above a species, in the animal or plant kingdom, is a family. (A genus is just a grouping of similar species together). We aren't seeing any new families (much less any new order, class, phylum or kingdom) forming. Anywhere. Ever. According to Darwin's so called Tree of Life and peer reviewed evolutionary literature, new Families have evolved. Over and over and over.
    .
    However, nature operates today as it did in the past. In the real world, with trillions of life forms around us, we never see anything developing above the level of a new species. Those life forms out there have purportedly had eons and eons of ancestors preceding them which should be revealing at least one example of a part this family "transitioning" to be a part that of another family. Again, we see stasis.
    .
    We only see "transitions" to those higher levels in the purely theoretical, unverifiable, ancient past, in the realm of evolutionary literature, and never in any life around us. If there is no evidence for transitions from one family to another – and please p(zrovide data if you know of any such evidence in the observable and not theoretical realm – then there is no evidence for evolution. And that's just for starters on how evolutionism defies real science.
    .
    Kindly don't say some fossil provides the evidence. It is easy to point to a pile of petrified bones and make up stories about how its invsible and evidence free descendants turned into some other life form. But if you insist, use a fossil. Name it. Then tell how you know it even had a descendant, much less one significantly different from it, much less one that crossed the family barrier. Name the family it is transitioning out of and the one it is transitioning into.
    .
    You are not a goo through the zoo update. You have a Heavenly Father Who made you in HIS image and likeness. He loves you and wants you to know Him, and to love Him, too. If you are an atheist and evolution believer, if you are anyone at all, He wants you to be His child. Forever. I know I found that out myself when I was an atheist and evolution believer who had never looked outside the box.

  26. I have a question about the peppered moths.  It was stated that most moths were white and only a few were black and that smoke caused dirty trees to favor the black moths.  It was then stated that the black moths prevailed and that was evolution.  We call that evolution but how can there be a change if the black moth already existed?  What are we saying changed? Is it the number of moths?  I always thought the evolution was white moths turning into black moths but the black moths already existed.  What am I missing?

  27. nature selection…and then someone crash into the most beautiful strong animal in the world then it's gone for ever!

  28. I passed my AP Bio test because of Bozeman and Jesus 😂 I had no idea what was going on most of the year, until the end when I fasted and binged this playlist 💀 I'm in college now ✌️

  29. Hi remmember I am a student from when you came to our class 3white mr. Kurtz remember me I am the student who asked you

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