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Current time:0:00Total duration:10:37

Video transcript

you may have heard of things like man is evolved from apes or maybe something like birds are evolved from dinosaurs but what exactly is this evolution and what causes it to happen well in this video we're gonna learn exactly what this evolution is by taking a much simpler example so evolution can be defined in many ways I like to think of it as change it's a change in something called the gene frequency gene frequency and we'll talk about what this is in a second off a population of a population or or generations or generations okay so a lot of fancy words over here right so to make sense of this statement let me tell you a story of beetles and crows so imagine there are some red beetles on a bush who like to eat these leaves and there are some crows over there which like to eat these beetles and so as this crows eat the beetles up their number decreases but these beetles reproduce and that keeps the population in balance so everything is fine and great until one fine day a green colored beetle is born and it's a little difficult to see so here is that green beetle all right now you may be wondering hey how come suddenly a green beetle gets born this can happen due to something called mutation mutation is where the genes that are being passed along from the parents to kids undergo some changes because of these changes some new traits are found in the kids so maybe the gene that is responsible for color underwent some change and because of that the the new kid got green colored these mutations happen all the time a realistic example is blue color of the eye that we see in humans that is also mutation so that happens all the time and if you're wondering why green color it's purely random so just to make this point clear let's say for some other parents different mutation causes that skin to become blue in color okay so mutations are random and that's important now let's see how this affects our population you see the green color beetles have an advantage they are very hard to see and I'm pretty sure you can see that okay so the crows also find them very hard to see which means their chances of getting eaten is less so they have a higher chance of survival compared to the red beetles and the blue beetles maybe and therefore more importantly they have a higher chances of reproduction and making more copies of themselves so as time passes what do you think happens see right now the green beetles are minority most of the beetles are red in color right but as time passes what do you think happens well because green beetles have a higher chances of reproducing compared to their red color cousins or blue color cousins we might expect their number to increase and that's exactly what happens as time passes by you will find that the red beetles start decreasing in number because they can be eaten very easily they can be spotted very easily but the green beetles cannot be spotted that easily and so they start increasing in number maybe the blue beetles also start getting eaten and before they have a chance of passing their DNA maybe they could completely wiped out that's totally possible because they were minority had no advantage and so they are completely gone and after few years or maybe many years we might find that all the red beaters are gone and only the green beetles have survived so let's think about what happened initially the red colored beetles were more in number which means they're the gene that is responsible for red color that was more frequently seen in every generation that was more frequently being passed on right so we can say initially or earlier these genes the genes responsible for red color had a higher frequency okay that's the meaning of gene frequency gene frequency means which genes do you more frequently see in every generation which gets more fast along so that was very nice to begin with because they were majority in number and the green and blue were very minority in number but as years passed and this can take many discs and then the amount of time it takes depends on a lot of stuff it can take few years or it can take a lot of years it can take hundreds of years so anyways after many generations what do we see now we now see that it's the green color beetles they have become the majority which means the genes responsible for green color that is now more frequently seen that is more frequently being passed long so now the green color genes they have a higher frequency okay in this population the red colors are gone they have become ancient you don't even see them anymore anymore only green color we passed on so this means can we see that there has been a change in the gene frequency that we see that's what we mean by change in the gene frequency right earlier rose-red now it has become green so there's a change in the gene frequency of the population of our beetles over generations right in other words in other words evolution has taken place so this is evolution from here to here this is evolution and so why did this happen what caused this evolution well two things one the mutation caused some changes in the traits that's one thing allowing different colored beetles to be formed second one particular variant the green color one had an advantage meaning they had a higher chance of survival and so higher chance of reproduction because of which their numbers started increasing and so this process in which the genes or the traits which have an add one and because of which they can start being passed along more and more and started increasing in number this process is what we call natural selection and it's called so because this happened naturally you see the moment you have an advantage naturally you will end up creating more copies of yourself and start increasing in number so what you're seeing over here is evolution by natural selection of course there are other ways in which evolution can happen as well which we'll talk about in other videos anyways natural selection is one of the major reasons why evolution happens and this idea of natural selection was first proposed by a man called Charles Darwin and because of its contribution today we call him the father of evolutionary biology okay now before we wind up let's look at some of the important features of evolution one important thing you can see is that evolution only makes sense over a population it's wrong to say that an individual beetle evolved that makes no sense it's the population of the beetles that has evolved secondly which is the most important point I should think that in evolution the nature forces you to change and adapt to the surrounding is that correct is the nature forcing these beetles to change no you see the changes are happening randomly due to mutation that has nothing to do with their environment that would have happened regardless of what environment these beetles were in okay so the changes happen randomly but the nature helps in selecting which of those changes should get transferred you know should get passed along in the future generation and should increase in number that's what natural selection is so Nature doesn't force you to change changes happen randomly but nature helps you in selecting which one grows in number now this might make you think hey the green variant is superior the blue areand was useless again that would be wrong way to think about it the green was superior only in this situation but let me show you a differ scenario what if as time passed on even the bushes started changing its color what if the bushes changed slowly to blue color now I know this might sound ridiculous I'm making this up but I'm trying to say that you know and Worman can keep changing and so think about it what if the bushes had changed its color then the green wouldn't be selected because they would lose that at one they wouldn't have any advantage now I'm pretty sure you would understand that it would be the blue that gets selected and so now the beetles will evolve into blue color so you see all those random variations were important these variations help prepare the species for our ever-changing environment and so if you have lots of variations you have lots of options for it to be selected and adapted to the environment that's of evolution works and so variations may not be very useful for individual organisms individual organisms might suffer because of the variation but for the species as a whole variations are super important it's because of these random variations natural selection can kick in and a species can adapt to various changes in environment so that's pretty much it let's quickly see if we can go ahead and recall what we learned so can you recall what is evolution what is natural selection who is called the father of evolutionary biology what causes variations and finally why variations are important for a species if you have troubles answering these questions no worries you can always go back and 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