Bozeman science: Speciation and extinction

hi it's mr. Andersen and welcome to biology essentials video number seven double o seven this video's on speciation and so it's really on just two things in other words it's how we go from one species to two and then how we go from one species to no species and so this right here is a tap with saurus it's a sauropod that was found in Brazil and you can see it right here in this phylogenetic tree and so if we trace the phylogeny of taboo asaurus what we would find is each of these points here represents a common ancestor of the dinosaurs above it but because it branches in either direction that means we're going from one species into two species and that's called speciation and we'll talk a little bit more about the mechanisms by which we can specie eight but essentially in speciation you go from one species to do an extinction is when you go from one species 20 species and so where do we find on that on here well on the side you can see we have time so we have time on the side so this is millions of years ago and so you see that some of these elend in other words niger asaurus right here ends and that means that it went extinct in other words this one species became 0 species and so in life we go from that first common ancestor of all life but we've gotten a diversity of life through speciation but remember also along with that we have a lot of extinctions in other words the survivors are surviving on the on the backs of those that don't survive and so this video is really only about two things but it'll be a little more in detail than that and so how do we get new species that's through a process called evolution or its biological evolution or change within a gene pool so there are two things kind of in play with speciation and extinction in other words when one species becomes to that species is evolving or changing or separating into two populations that are reproductively isolated and so evolution can give us diversity but as that environment changes it can force speciation and that environment can also force extinction and so there's this play between evolution and vironment and then speciation and extinction this remember creates more diversity and this actually creates less so taken to these extremes one specific type of speciation where you see incredible a rapid rate of speciation is called adaptive radiation that usually happens happens when we open up a new niche and likewise when you have a bunch of extinctions at one time we call that mass extinction and we've only had about five of those through the history of life on our planet so let's start with speciation and let me give you a real example of that and this is the three-spined stickleback three-spined stickleback in the study I'm looking at here was in Loberg lake which to kind of orient yourself here's Anchorage right here so we're in Alaska Loberg Lake is right down the road from Wasilla and so speciation occurred in the stickleback or is occurring right now in the stickleback the three-spined stickleback has three spines that go out the back but there are actually two different phenotypes or two different varieties of stickleback this would be a low armored stickleback and it's found usually in a freshwater environment but if we were to look at the stickleback the marine stickleback that spends half of its life in the ocean and then comes back to actually breed it'll have more armor on it so it'll actually have larger spikes it'll have additional spikes down here and then they have plates on the side so there are plates on the side of the stickleback that go all the way back here and so this would be what we call a fully armored stickleback and then if i get rid of the coloring that'd be a low armored stickleback okay so a natural experiment was done in 1982 so in nineteen eighty-two in loberg lake will say loberg lake looks like this almost all the sticklebacks in loberg lake were of the low armored variety in other words they were just this freshwater and so what happened in nineteen eighty-two is that they poison the lake because sticklebacks don't really have a purpose they too but they wanted to put trout and salmon back into the lake and they wanted them to grow and so they poisoned everything in the lake so they killed all the the stickleback seeeeee so there are no sticklebacks in the lake so it's a great kind of an what they found is that over the next few years fully armored sticklebacks were making their way into the lake and so they were making their way probably sue streams and out from the ocean and making their way back into the lake and so we had in here was fully armored sticklebacks and over the next few years their population started to grow eventually they started to notice hey there's fully armored sticklebacks in here and so what they found that over the next few years is is puzzling in other words the fully armored sticklebacks started to drop off their numbers started to drop off and then they started to see an increase in the low armored stickleback in other words their population started to increase to the point where if you go to Loberg like right now you're going to find almost all of the low armored sticklebacks and not many of the fully armored and so this is a kind of a cool experiment where you can actually see speciation taking place now why would you see that if you think about it for me i would think man more armor the better why wouldn't i want as much armor as i can but the predator that they were facing was one of the most scary projects in all of science if you were small so this right here is a dragonfly larvae and so dragonflies remember very beautiful but they spent a lot of their life underwater and they form it as a nymph aura or a dragonfly nymph and so or larvae and so this is one hunting this is a video from David Attenborough movie so let's watch him we feed Wow okay that's a little disturbing and so the dragonfly larvae is the major predator in loberg lake and so the low armored sticklebacks actually grow faster than the fully armored sticklebacks and so the fully armored sticklebacks were being preyed upon at a greater rate by the dragonfly larvae then the low armored sticklebacks and so we had natural selection taking place and so what we're starting to see is a change in that now eventually if fully armored and low armored sticklebacks can't interbreed then we have those as a separate species and so on that tree of life we can go from one branch to two now again taking to its extreme we can have what's called adaptive radiation and so once you have a new environment where species can take off and there's no predators you get a huge amount of diversity and so when we talk about evolution we have a tendency to fixate on the Galapagos Islands and neglect the Hawaiian Islands and so there's a great picture right here of the Hawaiian Islands um but what we found is that it was hard for a lot of species to get to the islands mammals weren't going to make it but birds could make it easily and so the honey creeper is an example of a bird that just went crazy on the on the Hawaiian Islands and so we think the ancestor of modern day honey creepers was a bird that looked like this it was somewhat similar to a Finch but once it arrived on the island it was a founding population you got this huge diversity of all these honey creepers you can see their beaks are each of them adapted probably to a different flower and so we had adaptive radiation so we had this noon it show up this new environment and they exploited excuse me of this new environment show up and they all exploited all these different niches and so you had this great diversity of of honey creepers now a lot of these are pictures and not actual photographs and the reason why is that human showed up and with humans than we had predators that showed up and they started to make a lot of those species go away and so extinction started to show up as well what's another famous adaptive radiation while I can think of a couple on one would be the arrival of mammals and so once the dinosaurs went extinct and mammals were able to grab a foothold they adaptively radiated to fill a bunch of different niches that were once filled by dinosaurs or adaptive radiation we could also see in the Galapagos as they move from island to island like the beak of the finch which is just one population on the Galapagos now this flip side of this podcast is the idea of extinction I love this quote right here it's the idea that ninety-nine point nine percent of all species that have ever existed are now extinct and so these are some species that are rock the quagga the Great Auk the stylus scene or the Tasmanian wolf these are all species that have gone extinct just in the last few hundred years um and and they did that as a result a lot of these as a result of human pressure this would be a golden toad that went extinct in the 1980s and so if we look on this tree of life each of these branch points here would be an area of speciation but each of these endpoints would be an area of extinction in other words that that once you have that last organism died of that species then you can't pass that on those jeans on anymore and so we would say it's extinct now the things that are alive today are called extend but if we look through the history of life we find sometimes that there are massive extinctions extinctions that go across all all right scientists have identified five different mass extinctions over time and they're labeled here with these yellow triangles this would be the Ordovician silurian extinction this would be the late devonian this is the permian-triassic extinction this would be the Triassic Jurassic extinction and then this right here would be the Cretaceous tertiary extinction and so what makes a mass extinction it's a it's an extinction where the this the the rate of extinction is just dramatic and so we also have other extinction events here within this um this one a couple of interesting ones that you maybe know about this right here would be the permian-triassic extinction this one is known as the Great dying and so of all the extinctions this is the biggest one during the great dying something like seventy percent of all land species and ninety-six percent of all marine species went extinct and there are a number of different causes of that probably the one extinction that almost everybody's familiar with is the Katie Orr Cretaceous Triassic extinction or tertiary extinction and so that's that the one where the dinosaurs actually went away and so with all of these extinctions scientists are trying to piece together what actually causes it and so a lot of these are suspects in other words the great dying formed at the same time when Pangaea actually formed and so scientists think that that had something to do with it but it could have also been volcanoes it could have also been oceans losing their oxygen and so these are all the different types of characteristics that could have led to mass extinction and so scientists are kind of piecing those together and figuring out which one of those caused each of these different extinctions the one that I want to talk more about specifically is the KT KT extinction or the Cretaceous tertiary extinction and the evidence there is pretty good this is where dinosaurs go away it's probably not super super accurate to say that there's a lineage of dinosaurs that continues today and those are called birds and so Birds a it's a it's a lineage of dinosaurs that continue today but most of the dinosaurs actually disappear at that time and so the point in the fossil record where they disappear is sometimes referred to as the Cretaceous or the KT boundary and and if we look below that we find dinosaurs and if we live a look above that we find no dinosaurs in the fossil record now you've probably learned that there was a giant asteroid that hit around that time and we think that it hit in the Gulf of Mexico we've actually isolated where that that crater is but what evidence would we have to show that this actually exists why isn't it something else like climate change for example well one piece of evidence is that down here we have dinosaurs above here we have no dinosaurs but we also have a level of iridium that goes around the planet so a thin layer of iridium that's found along this KT boundary iridium is really rare on our planet it's not very common but in asteroids it's incredibly common and so that's one piece of evidence that suggests that this asteroid input Pat could have led to the the disappearance of the dinosaurs so that's an extinction and so again to summarize we've got speciation where we make new species extinctions where we get rid of those and they're big at some times and their rates are really high it sometimes and really low at other times and mostly that has to do with changes in the environment and so I hope that's helpful