hello bisque 130 this is the beginning of recorded lecture 45 uh continuing on with Evolution we we got through a lot of important stuff in the last one uh but believe it or not there is more to Evolution uh that we're going to do in this lecture so let's start by talking about something called the Hardy Weinberg principle of equilibrium it's quite a wordy title here um let's look at Hardy Weinberg oh okay so this is Hardy Weinberg um it's a lot of math lucky for you and for me and for all of us if you take an upper level you know ecology evolutionary biology class you will certainly learn to do all of this it's actually not that complicated but uh for an intro class let me try to put this into uh non math terms Hardy Weinberg or the the Hardy Weinberg principle of equilibrium can be stated as the following AAL and genotype frequencies in a population will remain constant from generation to generation in other words we're not going to see changes from generation to generation in the absence of evolutionary influences let's read this again so um Al and genotype frequencies will not change over time if there are no evolutionary influences at work this is a no duh statement right so everything we talked about last time in in the previous recorded lecture was about how all these evolutionary influences you know whether it's natural selection uh or whether it's the founder effect or gene flow that evolutionary influences cause changes in a Leal and genotype frequencies from generation to generation well this is just kind of saying the opposite of that is you're not going to see changes if there aren't any of these evolutionary influences if there is no natural selection if there is no gene flow whatever another way to think about this and a much more common way to see this is that if these changes are observed and again that's where all the math comes in about counting you know population numbers in in AAL frequency stuff like that if changes are observed within po populations then that means there must be evolutionary forces at work and that's what the people analyzing these numbers then look for if if they're seeing changes in the illegal frequency in a population from generation to generation that must mean there are evolutionary influences at work and then the job is what are they what is influencing uh the evolution of these populations so yeah a very very wordy description here uh but in light of everything we talked about last time this this is kind of a no du it's just kind of stating stating the obvious if there are no forces there will be no changes if there are changes there must be forces making these changes happen quick summary there now let's look at how Evolution shapes overall populations so there are a few ways that this can happen summarized here uh but let's go through each of these one at a time to see what these graphs are looking at so let's start with something called stabilizing selection so stabilizing selection is defined in the key terms as selection that favors average phenotypes within a spectrum of existing variation so you have variation from one end of a spectrum to the other end of the spectrum the selection here is saying average is good this side of things is bad this side of things is bad whatever this phenotype is the average phenotype is best and is going to be selected for we need an example birth weight in humans so birth weight in humans it there it is a spectrum uh yeah if you pay attention to the units down here yep babies can be born you know three four pounds all the way up to 11 12 lb as it turns out the low end of this spectrum is bad uh you know low birth weight babies uh are you know more vulner more vulnerable to complications is how this is phrased and that's that's putting it pretty well um it's it's not great for babies to be born on the low end of things that is selected against um same thing with high birth weights it is also um likely more likely to cause complications as they're trying to come out or to you know the person uh that's been carrying this baby can have complications as well so the high birth weight is also bad uh it is this average that is selected for and as a population uh we have evolved to mostly give birth to babies in this sort of average Zone here these extremes still happen but this is by far the most common one because of evolution so it's it's shaped this population the average is selected for that stabilizing selection next one directional selection so this one also defined in the key terms let me read it as we look at this graph directional selection is selection that favors phenotypes at one end of the spectrum of existing variation so yeah you have an original population whatever the selection is it's saying the average isn't good but this one extreme is good one end of the spectrum is what is selected for example jaalas Cactus so yeah these things are they're related to pigs they're not the same thing as as uh as pigs they're sort of the um American uh Native version of of pig uh and yeah they like to eat cacti you know cacti have some some bristly spines on them most animals don't like to munch on them but they could chew through the spines they don't like them but they could they could eat the cactus despite the spines however if the cactus has a lot of spines it's not going to be worth it for these for these uh these javalinas they're they're going to tend to ignore cacti that have a high density of spines it's just too much of a pain to deal with and they'll go after a cacti with fewer spines so yeah there's a there's an existing variation within the cacti population of just how many spines you have if we have this selective pressure at work here um it's specifically eating the cacti that have fewer spines and Aid avoiding the ones that have more that phenotype of having a high density of spines is going to be selected for it's going to be good thing it's going to become more common uh so yeah this extreme of having a high density of spines is going to be selected for that's going to shape the population overall to have that kind of phenotype and the third one diversifying selection so again I'll read the key terms while we stare at this graph diversifying selection is selection that favors two or more distinct phenotypes within a spectrum of existing variation most commonly what this means is that there are two correct answers usually the two ends of the spectrum the average Is Not Great there's more than one right answer either extreme is good let's look at an example of this this is a black bellied fire Finch but there are many birds that experience this there's a spectrum of variation in just how big their beaks are as it turns out small beaks are pretty good at you know picking up small seeds uh big beaks are you know they're not great at handling small seeds but big beaks are great at cracking open tough larger seeds if there was a a middle beak uh the middle beak would be bad at both the middle beak would be a little too clumsy to to pick up and handle these small seeds but a mediumsized beak would not be strong enough to crack open the larger seeds that's going to be selected against these two extremes uh again two correct answers here uh are are both going to be selected for um that's what diversifying selection is two or more distinct phenotypes uh that are favored so again all all three of these just examples of how populations have specific shapes with regards to phenotypes in the population as a result of the selective pressures that are on them now so far all the evolution that we've talked about has been very small you know changes in you know beak size to accommodate the food in the environment or you know coat color in those squirrels in the recorded lecture last time uh but we have a term for this when we're talking about smaller changes the term for this is microevolution which if I can read the key terms micro evolution is changes in a population's genetic structure so it's not always very dramatic it's not always even anything that you can see sometimes it's just a genotype of things uh but yeah micro evolution is just changes in the genetic frequency the term macroevolution refers to larger scale changes the key term's definition of macro evolution is broader scale evolutionary changes that scientists see over paleontological time the thing that I want to emphasize is that both micro Evolution and macro Evolution are the same thing in that they are both Evolution these are both changes in genetic makeup of populations over time the only difference between microevolution ution and macro evolution is one of how long it takes how big of these changes we're talking about it's uh a sense of time so here is analogy time uh this is erosion you you got a drain pipe down here looks like it's hitting this concrete and over over a couple of years it's wearing down this concrete so you can see sort of the Pebbles underneath it this is due to erosion um the Grand Canyon is also due to erosion uh the only difference between this erosion and this erosion is you know this took maybe a decade this took millions of years um and so well this took many years um and so yeah we don't call this micro erosion and macro erosion they're both examples of the same phenomenon in the same way that yeah we have microevolution and macroevolution these are technically separate terms but really they're everything that we've talked about so far their natural selection and genetic drift and and gene flow these two terms just are used to refer to you know are we looking at small time scale changes or are we looking at how changes happen going back a really long period of time so we've kind of talked about macro Evolution so far in these recorded lectures uh we're going to turn our attention now to the bigger picture of things bigger changes so as we go into this we're going to be looking at speciation and new species and creating like really new things not just slightly different colored squirrels so before we head into that I think we need to Define what a species actually is and this is actually trickier than it seems uh there are many different ways to Define what a species is uh I'm going with the following one so the definition that I'm using for this class is a species is a group of populations that are capable of interbreeding and producing fertile offspring so interbreeding is sort of part of the definition this does not work at all when you're talking about bacteria or things that don't breed but for practical purposes this is a pretty good one so if they could breed and have good Offspring together uh viable Offspring together we consider them the same species if they can't different species example dog specifically poodle dog specifically Cocker Spaniel dog cocka poo uh and yeah looks very different than the parents these two parents look very different from one another uh but despite their phenotypic differences these two can have fertile viable Offspring together we consider them the same species dog here's another example donkey horse they got a lot of similarities but they they are pretty different in many ways uh they actually can have Offspring together producing something called a mule but the mule is not fertile it's considered a hybrid uh it can't have offspring of its own and so donkey and horse they can have Offspring but not fertile viable Offspring therefore donkey and horse are considered to be different species from one another and third example bald eagle African Fish Eagle very similar Lifestyles very similar diet very similar coloration in the body and the wings um they can't have Offspring together at all despite their similar physical appearances uh these are not the same species at all so this again there are other ways to Define species but based on you know having Offspring together that's a convenient way to define this so now we're looking into speciation forming new species yeah speciation is the process of the formation of a new species something different something new so in order for this to happen populations of the same species need to change need to evolve until they're so different from one another they can no longer interbreed again if we're using interbreeding to Define what a species is and what a different species is that's we we get new stuff uh by um evolving separate populations until they're so different they can't interbreed anymore there are two mechanisms for making new species one of these is called allopatric speciation let me read the key terms definition as we look at this figure allopatric speciation is defined as speciation that occurs via Geographic separation so during alpat speciation we have starting population something happens some sort of physical separation occurs maybe this is you know a volcanic eruption splits the island in two and now they can't cross from one side of the island to the other or maybe a giant earthquake you know rips open a Chasm here and you know these small little lizards can't jump from one side to the other whatever it is there is some Geographic barrier that separates these two populations and at this point these are the same species they're two separate populations but if you were to grab one individual from this side and move it over here they would be able to have fertile viable Offspring that's what that's why they're both green that's what that is meant to indicate but if you leave them geographically separated for long enough for a long enough time and they're not they're not doing gene flow they're not exchanging ideas they're not exchanging genetic information with one another if you allow them to be isolated for long enough they are going to accumulate differences they're going to experience genetic drift differently they're going to get mutations differently and so these differences can accumulate so that over a long enough period of time they have become different species uh they they've just changed from one another they've drifted apart by so much to where even if you removed the barrier or if you grabbed one of these lizards and plopped it over here they would be different enough to where they could no longer interbreed and we would consider them to be different species uh to to summarize that yep there's a geographic separation that means there's reproductive isolation no gene flow they are separated from one another and again this could be due to a physical change in the environment again some sort of geographical or you know geological thing changing the world around them or and I'll show you an example of this in just a second this can be due to dispersal of members to a new area but again when this happens there's reproductive isolation they've been physically separated from one another and yeah these two populations they're they're just doing all that coin flipping especially mutations are random genetic drift is random they're doing these random things independently of one another it's going to lead to differences that over a long enough period of time is going to result in speciation example time so let's look at a one of these um one of these geographical one of these physical changes in the environment so uh the Caribbean and the Pacific Ocean used to flow freely into one another until about three and a half million years ago due to tectonic plate movement the ithmus of Panama arose and separated these two bodies of water this is not a very long strip of land but I mean it's it's more land than a than a fish can cross uh and so this effectively cut off these two bodies of water from one another the fish on this side and the fish on this side are not experiencing gene flow they're not exchanging information and so they're going through all their mutations and genetic drift and stuff independently of one another and again this is three and a half million years ago that's a long time to do random coin flips and mutations and stuff like that if you look at the fish on either side of this ithmus today you've got uh you know a species of pork fish on one side a species of pork fish on the other side they look fairly similar they're both you know medium-sized fish uh but yeah they're genetic differences if you look at their genomes and if you try to mate them with one another they have been isolated for long enough enough they're no longer reproductively compatible with one another we consider these to be different species and again it occurred because of this physical separation uh this physical change in the environment um another physical change in the environment is actually my example from up here uh the Grand Canyon so it took a long time to form but once it has formed uh this is a pretty effective physical barrier between the critters on one side and the critters on the other the birds don't care you get the same species of bird on either side of the canyon but for you know these ground squirrels uh again they look pretty similar to the eye but if you look at the genotypic differences and if you try to you know have Offspring between these two uh yeah they they've experienced so much drift and so many coin flips separately from one another uh these are different species uh from one another on the South Side versus the north side and I did you know make mention this could be physical change in the environment allopatric speciation can also be due to dispersal of members to a new area so here's an example of that you've got the Mexican spotted owl and the northern spotted owl so I mean I I guess maybe there was a there was a rough year down here for these populations of Mexican spotted owls and and they were so desperate they just flew everywhere they could trying to find a new home and new resources and and new you know forests and uh and prey and you any of those owls that flew out here didn't make it any of the owls that flew out here couldn't make it but some of those owls flew over here to the West Coast and found a nice place to live they started a new population they started to spread up the West Coast um they're separated enough from the Mexican spotted owl to where again there's no gene flow they're not hopping back and forth on the weekends to exchange genetic information they are separated from one another I guess this would also be an example of the founder effect if we wanted to to analyze that but uh the important thing here is that they've been these two populations have been uh reproductively isolated for a very very long time and they've experienced again this these Gene U genetic drift and mutations separately from one another they've accumulated enough differences now they're different species Northern spotted owl Mexican spotted owl that's alip Patrick speciation so that was my example dispersal to a new area the important thing is there's a physical separation there's productive isolation this is in stark contrast to the other example of species the other mechanism of speciation called sympatric speciation let me read the key term's definition as we stare at this sympatric speciation is defined as speciation that occurs in the same Geographic space so there is no physical barrier there is no reproductive isolation you just have a single location and within that a new species arises so how does this happen well we need to take a bit of a step back and look at selective pressures once again remember selective pressures were any force that chooses who lives and who dies what's good and what's not good what is going to cause you to survive and reproduce or not survive and reproduce food sources are a very common example of a selective pressure you need to get food in order to survive you need to survive in order to reproduce but the thing about food is that there are usually lots of different foods out there and there are lots of different adaptations that help you get those different food sources so there this is an example of there not being one correct answer there are multiple different adaptations that can arise to make use of these many different food sources that are available so here's an example these are cichlids uh fish that exist within Lake Victoria but a couple of other lakes in the world as well and uh yeah from from a single sort of ancestral fish that that colonized these Lakes uh we see speciation going in a lot of different dire directions again they're all in the same area together no geographic isolation but here is a fish that makes its living scraping algae off of rocks uh it's not glamorous but hey it gets the job done the adaptations that make this fish good at getting this food are very special you know it needs Jaws for scraping it needs tough teeth for raking up that algae its whole body is sh and you know where where it's able to to uh you know how fast it needs to go doesn't need to go very fast it's it's just eating algae uh all its entire body has adapted to this lifestyle of this food source but if you look at a different cichlid like the snail eater that's a very different type of food it needs strong Jaws to crack open the shells of these snails so its body is going to be different um planked in eaters they don't need Jaws at all they just need to move move around constantly and filter out Plank and from the water um Fish Eaters need to be very fast and agile to hunt down fish that they can eat and you know all these other ones as well again there's no correct answer about how to cck liid these are all correct answers and selective pressure is pushing the fish in all of these different directions so you get a bunch of different fish all within the same area because because they're all going after different ways of living and again these differences it's not just in their jaws it's it could be you know in what time of day they're active and you know the the size of their their eyes to to spot the prey that they need or you know being able to spot algae don't need to be very bright to to spot algae all these differences will accumulate as they get better and better and better at going after very specific food sources until they are no longer inter a to interbreed with one another and speciation um another example of this real quick uh we see finches colonizing islands in the galpagos same sort of Story one ancestral Finch came here from the mainland there is not one correct way to Finch and uh yeah you get all these different species of Finch arising in the same geographic area going after different food sources you know going after small insects going after large nuts going after Cactus uh you know going after um let's see some of these are going after stripping bark from trees and grabbing insects underneath there uh yeah lots of different life Lifestyles um and lots of different birds s Patrick speciation can lead to something called adaptive radiation so adaptive radiation is to from the key terms speciation where one species radiates to form several other species and actually you know this this uh slide here that said stpatrick speciation this is also an example of adaptive radiation this was one ancestral Finch coming to these islands and over many many many years selective pressure pushing its descendants in all of these different directions again kind of looks like you know spokes on a tire r mediating out this one ancestor having many different descendants that evolved in in very different directions that's what adaptive radiation is and that happens uh often enough with s Patrick speciation especially when there are many many many different correct answers uh for how to live and yet at the end of the day despite all the differences and you know their their beak size and you know what time of day they're active and all that stuff they're they're all just still Birds they're they're all sort of medium small-sized birds and at the end of the day despite all these you know differences in these millions of years there's they're still very similar fish they's still very similar ground squirrels if we want to see big changes dramatic changes this is you know this is enough to cause speciation but if you want to see really big very different species we got to go back really far in time because these changes are going to take a very long time to happen if we want to look back millions and millions of years into the past to see how Evolution has played out we need to start looking at fossils so the key terms has defined fossil as the preserved remains Impressions or traces of a dead organism from a past geological age so remains uh obviously bones uh are remains and that's what most people think of when they think of fossils but you know the definition says remains Impressions or traces so yeah this could be uh you know Footprints or this could be you know the impression of a leaf we've got lots of plant fossils that are just sort of the impressions of the of the plant leaves that have been preserved it could be Ms this is uh what's called a coite also known as fossilized poop uh which can give us some important information about organisms we have all these preserved remains from a very long time ago are very important for looking at stuff and and and what the world was like and and the species that existed a very very very long time ago uh importantly the term fossil record refers to all the fossils that have been discovered today so when we talk about the fossil record we're just looking at all of the information that we have available to us now all the different you know Footprints and feather Impressions and bones and poop and all the stuff that we found so far all that is part of the fossil record importantly this is rare fossilization for something to die and for it to be preserved for its bones or its remains or whatever to be oberved in a way that can be dug up and analyzed millions of years later is an extremely rare event most organisms that have lived and died on this planet have not been fossilized The Remains have been broken down by decomposers other organisms and there's no trace of them ever existing at all so the fossil record is cool we've got a lot of very interesting important information about you know stuff that existed at some point but doesn't exist now but we do not have everything we will never have everything uh unless we invent a time machine I guess but I mean uh this this is a limited way of looking into the past because it doesn't happen very often if we're trying to analyze the fossil record and sort of piece something together and get a picture of what the past looked like this is kind of like putting together a jigsaw puzzle and you don't have all the pieces um well again we'll never have all the pieces most things have not been fossilized that doesn't stop us from doing this it just means that this is a very challenging exercise to do when you don't have when you don't have all the pieces you could still get a good sense of what the picture is you could still make some connections uh but yeah it's important to to understand that this is a rare event we're not going to capture everything now one of the things that helps us when we're trying to put together this sort of incomplete puzzle is we can figure out how old fossils are so we know the way you know Evolution works it's ancestors you know passing their genetic information on to their descendants and because we can know how old fossils are that really helps us in sort of ordering what pieces are at the top and what pieces are at the bottom that that helps us putting this to put this fossil together um I won't go into the different ways in which fossils can be dated uh deeper fossils are older than more surface level fossils they're more sophisticated ways to measure uh trapped uh radioactive isotopes within rocks and fossils to calculate how long ago those things were alive and walking around but I'm just going to suffice it to say that fossils can be analyzed to know how old they are that helps us to put them in order now the whole point of looking at these was to connect the past to the present to look at stuff that you know based on these bones and other things that we've dug up existed a long time ago and connect those things to organisms that are alive today so here's my statement examining fossils of closely related species can reveal evolutionary histories of modern living organisms and this is kind of the goal we know what we have today how did we get here so I'm going to walk through an example of The evolutionary history of a modern living organism starting with this thing artists Recreation based on fossils this is a very very distant ancestor to the modern whale and that is that's a bold statement because this thing does not look like a whale at all but evolution is about small changes so let's let's walk through this this this Indo highas obviously walking around on four legs um it is similar to Modern toothed whales like Oracle whales based on its jaw based on its teeth I I won't bore you with the details but uh the way these teeth are arranged is uh pretty unique for a maml and it closely resembles that of you dolphins and Oracle whales and modern modern toothed whales so that's sort of the initial connection of like huh this this thing looks kind of whale like but obviously it's missing some important whale features how do we get from here to whale well if you look closely at its bone structure and bone density uh you will see that it probably spent a lot of time in the water um organisms with high bone density like to to lurk around in the water and spend time in water it helps them walk around and not Float On The Water unintentionally so we can infer this thing you know could probably swim and spent a lot of time in the water it's not that weird there are organisms alive today that have similar bone structure and live a similar life now we can draw a line from Indo highas to pakicetus this is a huge difference this is a massive leap these things are very different from one another what you have to always remember evolution is small it is about small phenotypic changes little changes in bone structure or foot structure or skull structure Indo highas did not directly evolve into pakicetus there were many small changes in between these two but as I've said we don't have all those we don't have all those intermediates we don't have every single jigsaw puzzle piece in this puzzle so again I'm drawing a line from this to this there's 's a lot in between we just don't have everything that is in between so why are we drawing a line from this to this well we know that Indo highas is older and pacus is more recent and despite their differences there are a lot of similarities especially in the skull and in the tooth structure so it's thought that pacus is a descendant of this Indo highest so what changes have we accumulated now well for one it looks like it spent even more time in water based on its legs it was probably a very good swimmer but could absolutely still walk around on land another big difference that we see in pacus is the movement of its eyes towards the back top of its head again we see this in the world today we see this in alligators and crocodiles based on its skull structure this probably lived the same lifestyle as a crocodile or alligator an ambush Predator that spends a lot of time in the water mostly submerged you know looking to jump out and grab something with little eyes peeking out of the water and again there are enough similarities where we can draw a line from Indo highas uh to to pacus what comes next well again in the fossil record the next thing is something called ambulocetus many small changes between pacus and ambulocetus we just don't see all of those this is just the next one that is available to us in the fossil record so what's different in ambulocetus well based on how its limbs are articulated it looks like it spent almost all of its time in the water doing a whole lot of swimming kicking its legs swimming around kind of like a modern otter um you also see evidence man paleontologists real really look real closely at bones uh there's also evidence in the skull of a fat pad which AIDS in hearing while underwater so yeah this thing probably spent almost all of its time underwater and had pretty terrible Mobility on land and again we can infer that this is a descendant of pacus based Mo mostly on the tooth structure in its jaw the next thing that we find in the fossil record is something called Remington acus um yeah this thing was fully aquatic uh even worse on land uh based on the Isotopes they find in its bones it looked lived in saltwater so we're in the ocean now and based on the the bones in its back and its spine it probably didn't kick its arms and legs like an otter it probably arched its back like a modern whale um next in the fossil record we have rocus uh we're starting to see smaller limbs that look more like flippers we're starting to see a nostril that's making its way further back in the skull spoiler alert that's going to become a blo hole before too long and you know I'm not going to bore you with all the rest but we see you know flukes start to appear we see flippers as hind legs are reduced and and the rest again I won't go through every single one of these but there's a very robust fossil record to get to the modern toothed whale from something that doesn't look like a whale at all we get there by small changes and you know looking at the things that are similar from one to the next and and tracking these differences as they occur and again this takes an incredibly long amount of time this takes millions and millions of years of small changes accumulating to see these big differences um here's another example just to go away from Wales we could do the same kind of exercise looking at the Modern horse uh and again this shows the time scale here this is like 60 million years uh to get to this hierra etherium to you know modern horse yep it's getting bigger the tooth structure is changing the one I want to focus on is how the the limbs change uh you know from walking on its fingers kind of like a dog or a cat to bearing all of its weight on a single finger like a hoof and as this happens the side fingers start to grow smaller and smaller as they prove to be useless uh as it's you know just standing on one toe you don't need fingers on either side of it until we get to the modern horse which only has the one finger that it's walking on the the hoof it's lost those other fingers completely and again we see these gradual changes by examining this fossil record as always tons of of individuals in between this one and this one we're just working with what we've got we know which ones are older we know which ones are more modern we could place together things like this tracking evolutionary history and one one more real quick uh cuz it's not just mammals it's not just animals we can do this stuff with plants too looking at the impressions of these plants um you know preserved in rocks uh you know we could put together an evolutionary history for how we got to Modern flowering plants from much much more primitive plants and you know the evolutionary Innovations the sort of things that they built up along the way all of this is emphasizing this statement by looking at fossils of closely related species we can see the evolutionary history of modern living organisms how we got from this stuff that we dug up to stuff that is alive today and if we look closely at all of this stuff this can account for all the diversity of life on Earth again mammals plants insects all this kind of stuff uh if you take bisque 132 with me we're going to look at stuff like this uh looking at the you know the origin the evolution of all these different groups of animals we're going to look at stuff like this looking at UK carotic supergroups very exciting I know we're going to look at stuff like this which is actually all life on the entire planet is the the you are here star with animals but no we're we're going to look at this stuff if you take bis 132 because following these evolutionary histories is something we can do for everything to look at all life on Earth and I just I want to close this by emphasizing these are always small changes this is just microevolution but taken over a very long period of time everything that we talked about in the last recorded lecture earlier within this chapter about Al frequencies changing it's that it's that same stuff adaptations and selective pressure it's those same things just applied over an incredibly long period of time we don't have all the fossils we'll never have all the fossils but we could put together pictures based on what we have to try to understand how we got to where we are today from stuff that is not around today but had to have existed at some point because you know we've got fossils and and hoofprints and poop and and stuff like that available for it so okay this is where I close out lecture 4 five uh this is the end of the Evolution chapter uh and this is the the cut off for exam number four so exam number four is going to end after this it's going to include all of the Evolution chapter um yeah this is the end of 4 five