hi everybody we're back we're doing part three right so part two we talked about scientific method so the last uh part of the chapter is to talk about darwin evolution natural selection and then that'll be it okay cool so oops let me get this to advance here we go all right so this guy charles darwin here you know as i said in the in in part one you know he's the uh a naturalist he uh his famous of course for for writing on the origin of species where he talked about natural selection and evolution right and of course he got all of his data you know this is science after all he got his data on this voyage so he took that ship the beagle and you could see you went spent a lot of time in south america and it would it would it was a scientific uh exploration so they would they would do map making they would uh you know chart waterways and stuff like that so navigation and then they also uh stopped at different places and made a lot of observations collected you know plant species animal species and they would periodically ship things back to england so he did this five-year voyage he famously spent a lot of time in the galapagos islands here off the coast of ecuador um a beautiful place if you're ever interested in sort of a a natural style of vacation seeing lots of animals and stuff like that galapagos definitely should be on your list it is an amazing place uh definitely one of the best trips i've ever taken and the animals there have like no fear of humans so you can get unbelievably close to things and it's very cool anyway so plug for the galapagos and uh but anyway so he made all these observations and you know he was one of those people who you know the idea of evolution right you know we think of evolution as species changing over time he didn't come up with that concept that is something that had already kind of existed in the in the scientific literature of his day it wasn't a widely accepted uh viewpoint the the sort of standard line that would find it you would find in the textbook of course they didn't have textbooks in those days but what you know what i mean was that all of the species were created and they couldn't change but but he had read some earlier work even his grandfather had done some writing about evolution and so he kind of had that idea floating around in his head and as he was doing these doing these observations and taking this voyage he collected a whole bunch of stuff and you know got him thinking about how uh species could change if those who are interested in sort of history of science and biology he wrote a book called the voyage of the beagle when he got back in the 1830s and it was sort of a a record of his travels and stuff and um it's it's a bit of a slog reading but it is really interesting because you could see you know he would he did this voyage in the 1830s and he didn't actually write his main book on the origin of species until 1859 is when he published it and but reading his earlier book you can sort of see the ideas kind of moving around in his head so that was that was kind of cool um his main thing was the concept of natural selection right so if species are going to change if there's going to be change in species what's driving that change and so he came up with the concept of natural selection and kind of formalized it and collected a bunch of data to sort of back up what he was saying you know as we said he was doing science and the idea of natural selection you know your textbook definition is differential reproduction under natural conditions another a summary of that is the term survival of the fittest you may have heard that right the best adapted individuals the individuals who are best adapted for their particular environments they're the ones that survive and of course if you survive you get the opportunity to reproduce and pass on your genes and the less well-adapted individuals don't survive right you know you think of like antelopes running around in the you know in the plains in east africa you know there's a lot of predators there there's lions and hyenas and stuff that want to eat those things so the alert high speed fast antelopes those are the ones that survive they survive they pass on their genes the slow not too not too alert antelopes get eaten by lions and they don't pass on their genes that's the idea right and that really was his big contribution is that showing that evolution was something that actually that you have evidence for out in nature and showing that this mechanism of natural selection drives that evolution okay okay now darwin had a couple of um a couple of problems with this idea number one was the age of the earth right in darwin's day it was accepted scientific knowledge that the earth was six thousand years old okay and that came from some monk who you know studied the bible and sort of made a timeline looking at the major characters in the old testament and came up with you know six thousand years you know in genesis god creates the earth there you go everything's there okay so having that very young earth was sort of a problem with darwin's uh with natural selection and evolution because you know species evolving and changing is not something that happens before your eyes it's something that takes time and so with earth being six thousand that just it didn't seem like enough time so one person was a colleague of his was this guy named charles lyell right here's a picture of lyle here when he was older looks like a you know a well-respected english scientist with nice sideburns right and lyell looked at fossils okay and you know you know again we'll give you the sort of textbook definition fossils remains or imprints of a living organism right so here's some pictures of some fossils this is a thing called a trilobite these things lived in oceans uh around 300 million years ago you can buy trilobites today i mean i have a char here's a trilobite that i purchased on ebay right you know you can see a little head there cute looking thing okay uh here's another fossil i have this is a megalodon sharks tooth another ebay purchase right you can pick up these you can find these that are much much much bigger but of course the larger and more impressive the tooth the more expensive it costs you know this was twenty dollars a really big nice pretty megalodon tooth could cost you five six hundred dollars right so this was fine for me okay so obviously this uh this this shark's tooth is not currently alive megalodons went extinct about two million years ago but you know this was a tooth and looks like a shark's tooth and you probably can't see it but you know there's serrations on it like a regular shark's tooth i mean it's it's definitely a tooth right so this is remains of a living organism okay um so he looked at fossils and what lyell was able to kind of show you know he did this is a picture of a cliff face in in the southwestern united states arizona somewhere in there he looked at cliffs in england but they were different colors but they were similar in construction where you have these layers of rock and as you would expect the oldest layer of rock is down here the youngest layers of rock are up here and lyell was able to by looking at all the fossils you find in these different layers was able to kind of reconstruct the life history of an area and he was able to show that you had these periods of stability where the fossils wouldn't change then you would have these periods of upheaval where things would you know some fossil forms would disappear other new ones would appear and he kind of was able to sort of create this sort of life history of the area and it couldn't really give you exact dates of things but lyell kind of had the sense that the earth can't just be six thousand years old it must be a lot older you know there's no way that all of the evidence that he's been accumulating and he looked at hundreds of fossils i mean you know didn't just look at a couple of things this is another fossilized things they're called ammonites you can also buy these on ebay by the way um you know by looking at this and he found similar evidence and whatever you would find these rock layers you know he was able to you know sort of show that there's been a lot of change you know there's been a lot of you know long periods of stability and these periods of instability and you know there's been a lot going on and there's no way that that could have all happened in 6 000 years you know lyle kind of thought maybe the earth is i don't know 20 or 30 million years old at least something like that again he didn't have a method of actually generating a date right now you can actually do that today we'll talk about radiometric dating in chapter two and the earth turns out and this wasn't figured out probably until the 1950s it turns out the earth is much older than even lyell thought the earth is you know he was saying something like 20 to 30 million the earth is four and a half billion years old it's extremely old in fact much older than anybody really thought it was i have another piece of show-and-tell here that relates to the age of the earth if you're a science nerd you end up purchasing strange things on ebay right these are meteorites right so this stuff here these are meteorites all right i'll hold one up to the camera okay so this chunk of metal is this was flying around in a large piece flying around in space uh it was formed when the earth was formed right these things here are four and a half billion years old all right and it was this big blob of metal and it was floating around in space and it hit the earth and hit argentina about 20 000 years ago it hit pretty hard because it blew up into tons of pieces and you know these then you can find different chunks of this stuff and you could you know pick these up on ebay for 20 to 30 bucks and you have you can have yourself a little collection of meteorites that you know are going to sit in your desk drawer and you're not going to do anything with it although you know unless you're a nerd you think they're cool okay you can tell this isn't just a chunk of regular iron because the meteoric iron has a specific content it's mostly iron nickel with some other trace elements and you don't find that specific set of trace elements in just any iron that you would find on the surface so this isn't just melted cast iron or something like that this is actually a chunk of a meteorite right and you know you got to test it and certify it and all that stuff so this is you know this is what the earth is made up this is what our solar system was made up back when the planets were forming all right cool so lyell kind of helped ease charles darwin's mind in terms of the age of the earth right another big influence on darwin was this guy here thomas malthus right and malthus wrote about population growth and basically what he wrote was that as populations grow assuming these are biologically reproducing things so the greater the population size the faster the population growth right the easier example of that is think of like bacteria right now bacteria really simple because they reproduce in a very simple way we'll talk about in a later chapter but if you have one bacteria and then it's going to become two bacteria then it's going to become four bacteria then it's going to be eight and then 16 and 32 64 128 256 it's going to double every generation right so as you get more bacteria each time the population doubles so it's you know it's 500 then it's a thousand then it's 2 000 then you know later on then it's a million then it goes from a million to two million right so the bigger the population the faster the rate of increase and for those you remember from your math class this is called geometric progression right and so the population as the population gets large its rate starts getting super high okay so populations grow geometrically but populations need resources whether you're bacteria or ducks or people or oak trees it doesn't really matter you need resources whether it's nutrients or sunlight or cheeseburgers or whatever the way you get more resources is by spreading out right so resources grow in a linear fashion and populations grow in a geometric fashion and so the idea is is that if every individual reproduces your population would quickly outs would you know would run out of resources right and everything populations would crash and but why doesn't that happen but it happens because you know this assumption of geometric growth is based on the fact of everybody reproducing natural selection gives you a mechanism to show that well not everybody reproduces only the best adapted individuals reproduce so you can kind of stop this sort of overshooting of the population okay now there was a ton of influences on darwin i mean you can literally read you know big giant thick books about darwin and stuff like that i mean evolutionary biology is an entire spending whole career doing evolutionary biology okay so these were some things that kind of you know the data that he had collected over that five-year voyage the influences of malthus the influences of lyle the influences of other things he kind of put together you know this idea he knew it would be kind of a controversial idea so he didn't really publish it and then you know he published it in the late in 1859 is when he put out his book the origin of species kind of summarizing all the data he had and all of these influences together it was a big big thing he became a super famous scientist uh there were big scientific debates about evolution now evolution still is can be controversial for some people but in science it's pretty much it's a completely objective accepted scientific fact there was tons and tons and tons of evidence to show how it works and then detailed evidence and all that stuff i mean we're going to do just just a quick intro here you could literally spend a lifetime studying it okay so darwin publishes this book in 1859 and then darwin of course like everybody ends up dying and uh and you know he died in 1889 not that it's important that you know the date of his death after darwin though the you know biology still continued and there are a lot of you know after darwin a lot more lines of evidence showed up right the whole concept of genetics and dna and genes and how they're passed on and how they control things all of that was came out after darwin we're going to talk about excuse me we're going to talk about gregor mendel um in in a later chapter talk about the genetics father of genetics we'll talk about that stuff in chapter 12. and then you know you can continue go on and on and on you know we'll talk more about it in later chapters then if you take biology two you'll spend a lot of time talking about it okay now we'll talk about a few things here one thing that was happening in the time of darwin was this this idea of what's called comparative anatomy right so you look at these things humans cats bats porpoises and horses these things live in totally different environments and they have different adaptations and if you look at these sets of four limbs here you can see a human limb a cat's limb a bird's limb sorry a bat not a bird a porpoise and a horse they're built for different things but the underlying structures are similar you have the upper bone is one large bone followed by a pair of thinner forearm bones and then you have all these multiple finger bones right so in you know humans we have a hand the cat is turned into a paw with these claws in a bat the wing of a bat is basically just outstretched fingers with a membrane between them the flippers in a porpoise or a dolphin and then of course you have in the horse you've modified the foot especially to allow you to run okay and you can you can figure out evolutionary relationships by examining the the anatomy that underlies the the different species that you're looking at the last thing the book talks about in this chapter is to talk a little bit about molecular biology right here we're looking at the products of the genes themselves the products of the genes the bones the anatomy the structure whereas here you're looking at the actual genes right so you can look at either like differences in proteins or differences in actual genes and you can figure out relationships by looking at genes it takes obviously more technology than was available in the days of darwin right this particular example looking at variations in a hebrew and a hemoglobin protein whereas you can you could do that or you could also just look at directly the genes themselves and look at variances in gene sequences and reconstruct these phylogenys again you'll talk about this in in biology too and spend a lot a lot of time explaining it okay so that's the end of part three that's the end of chapter one so i'll see you guys in chapter two all right see ya