Well welcome to the first lecture of our evolution class. Today we're gonna try to understand what is evolution, and why is it important. We're gonna discuss Darwin's two great ideas and then we're gonna talk about why The Tree of Life is important for society and how evolution actually saves lives. So, what is evolution and why would anybody ask that? Well actually we ask it because many scientists look at evolution in different ways. Some think that change most be a heritable change. Some people look at evolution as the origin of new species, new kinds of organisms around the world. And then finally, people look at evolution in terms of descent with modification. That is, all about the change in the phenotypes, the appearance of organisms, appearance and DNA. And so, there are many kind of varieties of how people look and study about evolution. We can think about evolution being, evolutionary science being divided into kind of three categories. First, systematists asked what are the units of nature? Systematists go out, they discover new species, they describe them, they differentiate them from other organisms. Population biologists ask, well is this a population, is this not a population? And, how do we look at assemblages of species? Then, we ask the question, a big, big question is, what has been the history of life? And so, systematic biologists are very much involved in trying to piece together the genealogical tree of life, and we'll talk about that, soon. And then, finally, and it's actually in some ways the most important aspect of studying evolution is how have the properties and why have those properties evolved over time? And those properties can be behavior, can be physiology, can be the phenotype, can be genetics. And most evolutionary biologists today study this third question. Now, Theodosius Dobzhansky was a world famous population geneticist. Years ago in the 30s, he said nothing in biology makes sense except in the light of evolution. And that's been a kind of a mantra for evolutionary biology ever since. Now Darwin, as all of you well know, took a long, long voyage on the H.M.S. Beagle. He was out almost five full years. But, the formative time of that trip was South America. So he came in to the region of Salvador, Brazil today, and that's where he saw his first rainforest. Then they moved down the coast and out onto the Pampas near Buenos Aires and that's where he saw his first rheas.. He saw two different kinds of rheas and that became very important. Then he moved down to the islands down in the south in Tierra del Fuego in the Falkland Islands, and he moved back and forth there for a number of months. And went through the Beagle Channel, which was named for the boat. And then up the coast, there he saw things like the mockingbirds, which are very different on some of the different islands. Actually, the famous Galapagos finches are so difficult to tell out in nature on a particular island, what species you're looking at, he didn't pay much attention to the Galapagos finches. But he saw so many new things and he went inland and did a lot of geology work. And that also shaped his world view and when he came back he just, like a lot of us, he set up a home office. And his home office was in this small country village called Down and it was there, very soon after the Beagle, that he started hatching all his great ideas. And two in particular provide this framework of all of biology for comparison and prediction and it makes evolutionary biology extremely important for society. But he created these notebooks and these notebooks are phenomenal. So in 1837, he's looking at building phylogenetic trees, he thinks organisms are related in a genealogy that's treelike. And therefore he said, the affinities of all beings of the same class have sometimes been represented by a great tree. I believe this simile largely reflects the truth. So even in 1837, which is 20 years before the publication of The Origin of Species, he's starting to map out what that long, long argument for those 20 years is going to be. And so it's from this tree that we can think about descent with modification. Then he had another great idea, and this came a year or so later in a notebook. One may say there is a force like 100,000 wedges trying to force every kind of adapted structure into the gaps of the economy of nature or rather forming gaps by thrusting out weaker ones. And this is his whole argument in a nutshell, about adaptation via natural selection and competition amongst organisms for economic resources, i.e,, food, nesting places, and so forth. Now this figure you see on the screen is the only figure in The Origin of Species. And Darwin put it in there because a tree is very iconic about the history of life. And its icon of evolution itself and he was trying to send a message with this tree. But he got some really cool things in here. He has things diversifying and then, going extinct. And then some going up to the next level and diversifying still up to the present. But, he was trying to do several things with this. Show that there's a branching pattern across the history of life and that there's deep time, too. It's really, really an awesome diagram to be putting in The Origin of Species, and no one was thinking in these terms. Now, phylogenetic trees are very, very powerful mechanisms to look at comparison and prediction. This is a circular tree, and we'll talk about trees in another lecture. But, on this tree are all sorts of organisms called model organisms and they are used extensively in medical science and in basic biology, molecular biology, developmental biology. So they include things like the mustard plant, a fungus Saccharomyces, Caenorhabditis, the round worm. The famous, famous fruit fly Drosophila, various arthropods and insects and vertebrates and then bacteria. And here we are, right here, this tiny little sprig on the tree of life. Now, why is this kind of thing important?. Well, we study all these organisms because we think they help human health. The systems the bio chemical systems, the developmental systems, share similarities with those of us. Now if that's the case, it can only be the case because of shared descent with modification. So we study round worms and we study Arabidopsis and bacteria because they tell us something about ourselves, and they also help us design drugs and find ways to thwart disease. So, Descent with Modification is an incredibly important idea. He didn't develop it and all the grand things that we have today but it's the basis for all comparative biology. And it enables us to reconstruct phylogenetic trees and talk about similarity across those trees. And if you can do that, then you have the ability to make predictions. So something that happens in a fruit fly, may be very, very important for human health. And we can make those predictions and we can test them. But then a tree of life, as I will show you just in a few slides, can help us discover new lifeforms that have major, major importance for all of us. Now I'm gonna give you just some examples of why this is really important for all of us. In the late 2000s, 2007, a series of Yale undergraduate students took a trip to Peru for field work and they were collecting endophytes. These are small microorganisms inside plants. And they were taking these endophytes and culturing them, when they got back to the lab up in Yale, to find out what are the biochemical properties of these endophytes. And they found out that 74% of those endophytes were bioactive. And here's an example of what they found. So there's a fungus. Tiny, tiny little fungus that lives inside plants and it's called Gliocladium. And Gliocladium is really cool because it's also can be nicknamed a myco-diesel. Myco for fungus, diesel for diesel fuel. Because that little tiny fungus generates chemicals that are found in our normal diesel fuel. And they also yield antibiotics, anticancer drugs and a host of other by-products of all of their metabolism. Another really good example, here's how the tree of life helps us save lives, and this is one of the very first trees ever used to show where disease organisms come from and what they're related to. So, West Nile Virus erupted in New York City. It killed a number of people who were older and their immune systems were compromised. And it broke out in birds. And it killed a ton of birds. At our zoos and elsewhere. And no one knew what this was. This was an emerging disease. But what they did, is they sequenced some of its DNA. And then they built a phylogenetic tree. And they found out that the New York version, a variation of this virus was related to things in Israel, in Africa, in Italy, and down in East Africa. Then they began to understand its ideology and where it came from. And, that had broken out in Europe and elsewhere. And so they were able to identify it and then we followed this. It's all across the country now and it's a pathway all the way across the country. It has been tracked by phylogenetic trees and using DNA analysis. Okay, so here's a really cool example. In Yellowstone National Park are these very large hot springs. And in these hot springs are lots and lots of different kinds of bacteria and actually the color, the yellow color around it are microbial mats of one kind or another. And these hot springs have been explored by microbiologists that wanna discover new kinds of bacteria. And in order to do that they take samples and they build phylogenetic trees, and that way they can identify the kinds of bacteria and whether they're new. So on this illustration on the right, all those in red are new bacteria. Now this is important because in this hot springs was found some years ago a bacterium that is involved in what we call the Polymerase Chain Reaction. So it's the way we amplify and duplicate DNA for analysis, basic science analysis and lots and lots of clinical analysis. And that is important because that polymerase inside that bacterium operates at very, very high temperature. So we can replicate the DNA of any organisms using this bacterial nuclease time and time and time again, millions and millions of times. So that one little bacterium found in Yellowstone National Park has generated billions of dollars of economic activity over tons and tons of different kinds of bio-tech companies. So, there's take home messages. First, Darwin had these two really great ideas, descent with modification and adaptation via natural selection. We talked a little bit about descent with modification and we'll look at that more in upcoming lecture on phylogenetic trees. And then we'll also explore more adaptation via natural selection. But a good take home point here is that all of this work Is very important is saving people's lives. Evolution saves people's lives. That is not just an arcane science. We use evolution in our daily lives in many, many ways. I've given you some examples already, and we'll see many more examples in subsequent lectures.
