Hello students this is Plants and animals of southern California still. Okay and now I want to give you kind of my next little episode in our developing dialogue about natural selection and adaptation. So this one you might think of as the extended phenotype. There's this book written by Richard Dawkins and if you're just dying to hear more about this over winter break then this is a great book, it's a really fun book and it'll make you think about things in a much more surprising and profound way. But anyway I'll give you the gist of the book, the extended phenotype. So let's just think about you know kind of our normal adaptations like you might think that these desert plants are living in a very arid spot and so if you had variation among individuals in the population for how waxy the outer surface of the leaf is then that would have pluses and minuses. The waxy surface would keep water in but it would also slow down photosynthesis and in a dessert environment individuals that had more of a waxy surface and so they lost less water then they would leave more offspring, they would survive more and leave more offspring and so the genes that make for a waxy surface would spread the population. So that's the same old story that we're always telling. Okay now let's consider a trait that's not the waxy surface of the leaf, it's so obviously part of the plant. Now let's consider the spider web of a spider and the spider web of a spider of course is made by the physiology of the spider making spider web material but also by the behavior of the spider where the spider is waving a web and if you had a population of spiders and in that population of spiders there was variation for how tightly woven it was, whereby those spiders that put their lines in the weaving closer together, they caught more flies and they were able to make more babies, then the genes for the behavior of making the spider web more tightly woven those would rise up in frequency in the population and so you can see that even though the spider web is made of a material that's not exactly part of the spider, still the ornate adaptations that are so wondrous in spider webs, the beauty of spider webs, the complexity, that is an extended phenotype of the spider, like clearly that belongs to the spider and we would attribute that adaptation to the spider. Okay so now we'll go a little bit father, add a little bit something different. So if you go out to places where there's a lot of water, not in the desert but in the mountains, then you might find beaver dams and where the stream is flowing in a kind of flat place the beavers have cut up a bunch of branches and they dammed up the water so that there's a pond in the back and using that pond they can then move vegetation, float vegetation around, they can go off to one side of the pond and gnaw down one branch and then drag it, float it through the pond over to where they're living and then they can gnaw on the inner bark of that branch. And so the beaver dam and the pond, that's an adaptation and it's an adaptation of the beavers. Even though it's kind of this inanimate thing right? It's this thing that's you wouldn't necessarily think of as being alive but its part of the extended phenotype of the beaver. Like it's because of natural selection on genes in beavers that you get beaver dams and beaver ponds. So we've just taken one little step farther out from the spider web and understanding how the long stretch of genes extends to this extended phenotype which makes for all of the ornate adaptations that natural selection results from. Okay so now we can go take it just one more step and consider these galls, the galls on these junipers and the galls on these junipers you might at first like before you took this class you might go up to a gall on a juniper and think oh this is part of the plant because it has cells that have cell walls and stuff like that and you know it kind of looks like it's part of the plant but if we're trying to attribute to which organisms genome does this ornate structure belong it's not really to the plants genome, it's not really to the plants genotype. It's the extended phenotype of the midge that is making for the gall because how did this thing come to be adapted? It came to be adapted because in the long lineage of midges that did this type of thing there were midges that varied in what kinds of chemicals they secreted from their bodies and there were some midges that secreted chemicals that were a little bit that happened to be a little bit like plant hormones and there were other midges that just you know secreted the normal saliva and pea and whatever you know that they make. And so what we must imagine that in the ancestors and the history of the midges there was a time before they were really gall formers, when the population varied in this way and those midges that secreted chemicals that made the plant react, those midges survived better and reproduced better and passed on their genes including the genes that made the plants react and that spread throughout the population and there were additional mutations that occurred and those additional mutations made the chemicals even more like plant hormones and those spread throughout the population because they made the galls even better for the midges. And so we have these very elaborate cool gulls that are often specific to the interaction of the organisms involved and they're highly complex things that you don't think could have just you know arose as a cancerous you know like reaction with no adaptation. So you look at them because they're wondrous and you think oh this is the hand of natural selection and it's the hand of natural selection on the genes and the insects that are making the galls. So the galls are the extended phenotype of the midgets, not so much of the plants. Although you might say it's a little bit of the plants right? Because the midge galls probably have a little bit of a negative effect on the plants right? And so that would affect the fitness of the plants and so you could imagine, I don't know if it's the case with junipers and midges on junipers but you could imagine in other parasite situations that the host would have been under natural selection to become less reactive to the parasite and then the parasite would be under natural selection to send a stronger signal to the host and so there could be this kind of coadaptation between the genomes of the host and the parasite and so in that case you might say that the outgrowth, the thing that made it the way it is belongs to both of them. So there is some possibility for that type of thing in the extended phenotype. Alright, that's all that I have to say about that.