Life History and r/K Selection

by Jason Amores Sumpter
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the traits and characteristics in a life table that will affect an organism's ability to survive and reproduce. But that organisms life history. Now this are these traits will result from natural selection toe optimize fitness, and this is going to require trade offs between reproduction and survival. So we're gonna look at some different reproductive strategies right now. In the first two, I want to talk about our Cemal parody and Itera parody. Now, symbol parody is like, what, for example, salmon do where they have many offspring once right before they die. And you can see this strategy of Cemal parody in this chart behind me here, I don't want you Thio, you know, worry too much about what's going on this chart. It's actually like an economics analysis. Eso It's kind of beyond what you know, the scope of what we're trying to dio. All I want you to see is that in this chart, the reproductive effort the organism puts forth is going to maximize the offspring it produces and minimize the offspring for gone. Those You know it, uh, those that would come at a cost of speak. Now, with Itera parody, we have a reproductive strategy, where an organism has offspring multiple times throughout its life. For example, what humans dio And here again, we're going to see that in this strategy, the organism is going to maximize the number of offspring produces and minimize its costs to have, you know, an optimal reproductive effort. Now, another way that people look at reproductive strategies is R K selection theory, and this is basically looking at the traits of an organism. Is a trade off between quantity of offspring and quality of offspring. So with K selection, which again is what you see in humans or, for example, whales right behind me, the organism will invest more heavily and fewer offspring. That way, each offspring is a higher probability of surviving to adulthood, so it's a greater investment in fewer things. But you you know you have a higher chance of getting those offspring to adulthood. Now, these species tend to live close to the carrying capacity of their environments, and they tend to live in mawr predictable environment. So these aren't gonna be environments that have crazy fluctuations and all that. Now the offspring of these organisms require extensive parental care and usually take longer to mature to adulthood, you know, think about how long a human parent raises their offspring, you know, years and years and years, and it takes humans a long time to reach adulthood. Now these organisms, generally speaking or larger and also tend to live longer. But these air just trends. Of course, there's always exceptions now with our selection. You know, like you see with this mouse right here, the organism will produce many offspring, but there's a low probability of surviving to adulthood, so these species basically invest in greater numbers of offspring and tend not to invest is heavily in each individual offspring. Uh, the species tend to live in less stable environments, which is why the ability to reproduce quickly is important. And in fact, you know mice, for example, can have offspring multiple times in a year. So these species have high fecundity, and a short generation time doesn't take long for one of these, a little kind of yucky to be honest. Little yucky mice grow up to be a new adult mouse, and, uh, uh, sorry. So the offspring mature quickly, and the offspring reach adulthood and can then have their own offsprings of short generation time. Uh, so they also do that quickly. Now, organisms that use our selection just a trend again tend to be smaller and have shorter life spans. So here, with that survivorship curve we were looking at before, hopefully you realize that humans are going to be case organisms that use case selection in these frogs or organisms that use our selection. So with that, let's go ahead and flip the page.