BIO1A03

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I All right.

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All right, we're gonna get started. OK. Uh, I'm gonna turn this up a little bit. Can you guys hear me clearly in the back? Yeah. OK perfect uh quick announcement coming from the Mac Bio Society so there's an undergrad led uh group uh of students, um, where they get together they share resources about biology programs and get to know one another, um, so they're actually gonna have their first formal um. Uh, events, um, happening Friday, January 31st, 6 p.m. um, if you'd like to get tickets for that, the QR code is there and I've also posted this on the A2L announcements page, um, so you can get the details, um, on there as well. All right. So jumping ahead to where we left off yesterday. OK, so just to reorient yourself, so we're talking about three of the greatest unifying ideas in biology. So today we're gonna complete the Life is Cellular, um, one of the theories, um, and then hopefully we'll get through life processes information. So then on Friday we can spend the whole day talking about evolution and then for the subsequent, uh, 5 weeks we will also continue to talk about evolution. OK. So we're going to talk about two competing hypotheses when it came to self theory, um, and so, um, rather than sort of pulling the group, um, I just want you to take a brief moment, um, to jot down the definition of a hypothesis because this is gonna be something that's gonna be important um for a lot of the activities we do as well as for testing purposes so make sure you know you're familiar with the definition of a hypothesis and how it be different from a theory which we covered yesterday. Um, and the textbook, uh, chapter 1.1 will give you the definition. OK, so a hypothesis is a testable statement that explains something observed. So it is uh based oftentimes on a single observation whereas a theory would be based on a bunch of observations that are all corroborating with one another to explain something a little bit more general. So that's how they how a a theory differs from a hypothesis. An experiment, which is another definition you should know, it allows researchers to test the effect of a factor on a particular phenomenon, something that you can measure. A prediction is a measurable or observable result that must be correct if a hypothesis is valid. So students, uh, often and and actually not just students, even scientists will sometimes use hypothesis and prediction interchangeably, but we're gonna actually spend a little bit of time talking about the distinction between those and why it matters for when we go and and start thinking about experimental design and setting up our experiments. OK, so One of the simplest ways to think about the distinction between a hypothesis and a prediction is if we formulate our hypothesis in a very specific um way. So if we formulate our hypothesis as X, so X could be some explanatory or independent variable that we might be manipulating in our experiment, for example. So X affects Y and Y would be something that's um it's the response. So it's a dependent variable. Something that you can observe and measure. So X affects Y. That is the format that we're gonna use for this course when it comes to uh um stating a hypothesis. So really, really important to ensure that it's different from the prediction which would be, for example, it could be X increases or decreases or reduces um why. So it's a direction, it's implying a direction um if the hypothesis were to be true. OK, so predictions imply direction, hypotheses do not imply direction. And predictions, um, Only come about if the hypothesis itself is valid. OK, so this is something we're gonna practice a lot with, um, in the next few slides as well as on Friday. So if it's not super clear what the distinction is right now, I'm hoping that it'll be quite clear after we get some practice. OK, so the two competing hypotheses, um, one that had been around, um, for quite some time up until the mid 1800s was, was this idea of spontaneous generation. So this was the um hypothesis that organisms could arise spontaneously under particular conditions and that bacteria and fungi which they wouldn't have actually known in the 1800s exactly what those were but those are the names we'd give them now. Those that spoil foods such as milk and wine would spring to life from nonliving materials so they just sort of spontaneously arise and then give um uh rise to um additional growth or or cell proliferation. So that was the prevailing paradigm what um individuals at that time would have thought occurred. Whereas cell theory was the challenging hypothesis, where all organisms are made of cells and all cells come from pre-existing cells. So those two statements, all organisms made of cells and all cells come from pre-existing cells. Those are two testable statements. Does anyone know who came up with the original cell theory and did one of the most um famous experiments on this? Uh, yeah, I see your hand. Sorry, Pastor, yeah. And we will talk about his experiment right now. So he um was making a hypothesis that would state cells arise from cells and cells do not arise by spontaneous generation. So it's sort of rejecting the idea that cells could just arise spontaneously from non-living material. OK, so here's a bit of a challenging question. It's OK if you um don't get it on your own. How could you rephrase Louis Pastor's hypothesis into uh into an XXY type of statement? So in this case it could be X is required for Y. So take a few moments here. You can you can chit chat amongst yourself for a minute or so just to see if you can try to rephrase this in the specific formula that I've given you for a hypothesis. All right. Hopefully you have a few ideas. Is there anyone who's willing to give uh a guess to or or their response of what you came up with? Yep. How many cells grow out of it. So X is the presence of pre-existing cells. Why is how many cells are gonna grow from that. Awesome. Did anyone else get something different? Or some variation of that. OK, awesome. Well, you nailed it so presence of preexisting cells um could lead to cell growth. Now it's totally fine if you said um cell proliferation or um further cells would arise from that, whatever sort of variation you put on that. But basically the important thing here is that we have our X, something that we could manipulate for example, and then why something we're measuring something observable. And then putting it into our formula for a hypothesis, then we can actually start to think about well how would we go about testing that hypothesis. So the hypothesis was stated would be the presence of pre-existing cells is required for self growth. The null hypothesis, so it's how you know that your uh hypothesis is formulated correctly is because you could often just put is not in front of the effects or is required um and then it makes sense and it's not implying a direction. So the null hypothesis would be the presence of pre-existing cells is not required for cell growth. The predictions that come out of this would be, so outcomes if the hypothesis were valid would be that cell growth will only be observed if preexisting cells already existed. Cell growth will be observed regardless, whereas the null hypothesis would state that cell growth will be observed regardless of whether preexisting cells. Already existed so this would if anything actually I would change the predictions to outcomes because these are the different outcomes that could possibly happen from the experiments um and one of them would support the hypothesis that you you um sell uh presence is required to get further cell proliferation. OK, so So we are thinking about how to formulate a hypothesis, thinking through the outcomes of an experiment that would allow us to validate that hypothesis or not. But what about going and testing that experiment? Yeah, I, I see it in there.

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Characters between these type of pieces in the prediction because I don't.

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Yeah, so in this case, the, the prediction is not implying direction, but it is providing an outcome. So cell growth will only be observed if preexisting cells already existed. So it's stating an outcome of the hypothesis that, so the testable statement that the presence of pre-existing cells is required for Cell growth. If that was valid, then cell growth will only be seen if there were cells, um, there. So it's an implying uh uh outcome of the experiment, whereas the null hypothesis is the second statement. So cell growth will be observed regardless of whether preexisting uh cells already existed. No worries. Again, when we get into more examples of this, um, in some instances predictions will imply direction but not in all cases and in this case, a prediction is just the valid um outcome of the supported hypothesis. OK, so what Louis Pasteur did was a fairly elegant experiment where he took two types of flasks, a straight neck and a swan neck flask. And so you can kind of see if you can see my cursor here. So in one case, we have this sort of um little bit coming off of the flask opening and this one is just straight. Um, he added broth to both that had um been sterilized. So boiling kills all the microbes, therefore sterilizing both. So they are treated both the exact same way. But then in one of them he he he's just allowing those to kind of sit um and um. You know, for, uh, either dust particles or whatever to um interact with the flask. So in one case, dust particles carrying microbes could enter the straight neck flask, but not the swan neck flask because they would actually get caught in the opening. So those cells that are just in the environment would not be able to um get into the broth. So basically the swan neck is excluding the presence of pre-existing cells, whereas the straight neck is not. Um, at the end of the experiment, um, it, he found that in one condition that the broth remained clear and sterile, so no microbes appeared. In the other, uh, flask, broth became cloudy because of the growth of microbes. OK, so based on the results from this experiment, would the null hypothesis be rejected? Why or why not? So who would say that the null hypothesis would be rejected based on the results of this experiment, just with a show of hands. OK, and who would say that it would not be rejected. In other words, that the hypothesis is invalid. Mm, OK. So I think in this case it was pretty clear that the presence of pre-existing cells, which would have been found in the straight net class, so the microbes would have colonized and then you got further growth which is shown by the cloudy color. So often the cloudiness of broth indicates how many cells have proliferated, so that's something you could measure. Um, and in this case it was only in that condition in which preexisting cells had been present in which that cell growth had been observed so it's, it's validating or supporting the hypothesis. Also just a side note, we'd never prove hypotheses we either have support for them or not, um, and in this case though, we would be able to reject our null hypothesis. Which was stated previously in the previous slide that cell growth would be observed regardless of whether preexisting cells already existed. So in other words, it's pretty conclusive evidence that the uh presence of cells were required for that cell growth to be seen, which, uh, suggests that his hypothesis is well supported. And of course, nowadays we have yet to do an experiment where this has not been shown over and over again. So it's fairly robust experiment. Any questions on that before we go through a quick recap? Yep. Hm. That's a good question, um. Because there's no like. I think the the more evidence you have for something, especially when it's, you know, collected independently for example by different research researchers there we can build a consensus um and then maybe that could be could could be accepted as fact, um, but in some instances it's really hard to sort of delineate like how many experiments do we need in order to say that something is a fact or not but we could say that a hypothesis is is really well supported or um. Has been around for quite some time and we haven't been able to reject it but the goal is always in science to be able to falsify um uh uh a experiment or a test but um in this case um it's it seems to be you know now that we also understand the mechanism of that which. Also corroborates why he got the outcome that he did. It all kind of pieces together that this is sort of accepted as fact now. Does that answer your question? So yeah, not a very straightforward answer, but, um, impressing upon you that when we call something a fact, there's no like specific criteria we're using for that. OK, so really quick, uh, recap here, uh, what does it mean to say that something is alive? There is no single well accepted definition of life. Instead, we can identify common characteristics that most organisms share, but nonetheless, there's always gonna be exceptions to those rules. So we could consider some organisms living even if they didn't have one of the three, characteristics, for example. And then what we're introducing now is three of the most influential unifying ideas in biology cell theory, chromosome theory of inheritance, and theory of evolution. And that we spend a bit of time talking about life emerging from cells. So cell theory identified the fundamental structural unit common to all life. OK, so we're going to get into chromosome theory of inheritance again. I'm being quite brief on this topic because a lot of it should be reviewed from, uh, potentially a course that you've already done, um, but I'm trying to kind of take you from there to evolution so you can kind of see the connection between them. So we're asking the question how is hereditary information transmitted from one generation to the next? So the chromosome theory of inheritance was proposed in 1902 by Walter Sutton and Theodore Bovary. One thing I want to point out is that I won't be testing you on dates or names, so don't spend too much time completely memorizing this, but nonetheless, I still think it's really important to think. About how the ideas that I'm presenting in class when they came to be um and how long they've been around for because that actually gives us a lot of information about how robust some of these hypotheses are um so again don't memorize the the names and dates but nonetheless I'm gonna include them because I think they're still important for you to know. Um, hereditary or genetic information is encoded in genes, so that would be a definition that you would want to be familiar with. Genes are units located on chromosomes and in the 1950s, um, it was discovered that chromosomes are molecules of uh deoxyribonucleic acid or DNA. Um, and DNA is the hereditary material. So actually before we even knew anything about the molecular makeup of DNA, um, hereditary material was sort of thought of, um, almost as like a philosophical theory about how things are transmitted, how information is transmitted, but nonetheless, in the 1950s is only when we actually understood the mechanism of that and that's not that long ago. So genes are segments of DNA that code for sell products, um, and I'm going through this pretty quickly because it's proportional to, you know, how much time you should be reviewing this material, but nonetheless, it's important to set up. So each strand of a double helix, um, is made up of 4 building blocks so we have A, T, C, and G. And the sequence of this code um is like letters in a word um so again if you're gonna take genetics or another course you're gonna be very familiar with um how these code for proteins like the process in which that happens um so DNA carries or encodes information that's needed for an organism's growth and reproduction. The two strands of the double helix are held together by connections between the blocks. So it's a very specific pairing. So A pairs with T and then C pairs with G, and then this allows this pairing allows the DNA to be copied. And it preserves the DNA, uh, the information encoded in the DNA. So think about copying, um, right? So we're actually, if we're going to replicate, if the cell is going to replicate, all of the DNA has to be copied with some degree of fidelity. Um, James Watson and Francis Crick, along with Rosalind Franklin proposed that DNA is a double stranded helix. So this was again something that we didn't actually know about, um, for quite some time until around the 1950s or so, and I did include a video on the A2L all about the double helix and it's, um, discovery on A2L, yeah. OK, so here is where I want to spend a bit more time really starting to think through why DNA matters when we talk about evolution because maybe for some of you that might be a very obvious leap, but um it's important that we spell it out and take some time. So genes and DNA code for information necessary to produce a functional product often a protein. And then DNA is inscribed to RNA um to uh RNA message, and then the RNA message can then be translated to a protein. So the central dogma is sort of describing this process in which genes are encoding information, the DNA is transcribed into RNA first and then RNA is then translated into a protein. So think of that flow of information. And then at the end the outcome would be some sort of outward appearance of the organism. Oftentimes there are many of course functions that you wouldn't see in outward appearance but in a lot of the traits that we're gonna talk about when we talk about evolution, it's gonna be traits that um you can measure, you could observe, you can um see if you're studying these organisms. So DNA is copied to pass genetic information from cell to cell or from one organism to its offspring. And remarkably, copying DNA is highly accurate. Um, but nonetheless, mistakes are made at some, uh, degree of probability. So the big question, and then this is why when we think about evolution that's so important is what happens when a mistake is made? What is the consequence of that? Um, in some instances, uh, a change or, um, maybe it could be what we call a single nucleotide polymorphism that I'll talk a little bit about in a few weeks' time. So you could have a small change that could potentially lead to changes in proteins. And that could impact the outward appearance of organism because it's a product of protein. So in other words, it can actually impact the traits that an organism is displaying. So it could be morphological, physiological, behavioral. DNA sequence changes may cause changes in outward appearance. And so the question then is how does this central dogma, so this flow of information help us understand how mutations so those changes in the DNA can result in disease? So this is something where you wanna think through in terms of that flow of information um and understanding how mutations. Actually relate to outcomes such as disease so I'm not gonna uh take this up as a group um today but it is something that you might want to um highlight in your notes is something that you should start thinking about so then if you were to ask be asked this on a short answer question for example on an exam you might have a response for it. OK, so really quick, um, review. Um, life processes information. So this is one of the three, unifying biological theories that we've been talking about. The chromosome theory of inheritance states that genes are located on chromosomes. Chromosomes consist of a molecule of DNA, which is the hereditary uh material, and genes are located on chromosomes that consists of specific segments of DNA, um, coding for products in the cell, and then the flow of information from DNA to RNA is called the central dogma. So here's the critical point that I'm trying to build up to that imperfect replication, also known as mutation, which will be a definition we'll go through quite a bit in um a couple of weeks' time, provides the source of heritable variation in traits. So the thing that can be passed. On from generation to generation is found in the DNA and that this process this imperfect replication is the source that fuels evolution we have to be able to have heritable variation in traits in order for evolution to occur OK. All right, so I'm gonna check how we're doing for time here. Which is awesome because that means we can spend a lot of time on Friday with our activities. So in the next few slides I'm going to give you um sort of the introduction to evolution. It took us a lecture and a half to get here, um, but again just kind of setting up some of the basic terminology, the concept itself, um, and then we're gonna spend a lot of time getting into the nitty gritty from here on in, and the question that we're asking is where do organisms come from? Um, section 1.4 in the textbook will introduce a lot of the concepts here. OK, so this one we are going to take a little bit of time to chat about. So if a non biology major friend, also many of you might not have declared your majors yet, so you might be in this category, um, if someone had asked you what is evolution, what would your initial response be? So gut reaction um so what I'm gonna do is take a couple of minutes this time um and you can chit chat with someone next to you or if you prefer just sort of writing your own response to this, um, down you can do that um and then I'll, uh, solicit a few responses from you in a few minutes. All right. OK. So If there are any brave volunteers, what did you come up with? Yeah. Some changes over a long period of time. Awesome. Changes in in what? Just a little bit more specific. OK, OK, so, uh, changes in, in organisms, um, and their traits, um, over a long period of time, awesome. Other responses. I see a hand up in the back. Adaptation and then. What what would be the definition of that? OK, so I think I heard the last part of what you said, but basically there's some change in the environment and it could be sort of traits that are, uh, responding to that and maybe you, uh, have a more favorable outcome in that environment. Did I capture what you said or OK good awesome. Any other responses? Yeah. Randomly occurring mutations that are passed down in advance. Species are more likely to survive to age. Awesome. OK, so you're, you're bringing in sort of the idea of mutation, so the heritable, uh, source of variation, um, that, uh, is passed down from generation to generation, um, due to it being, um, potentially beneficial and increasing survival. Awesome. So basically I've done my job. I can go home now. I don't need to talk about evolution um, those are excellent responses. Did anyone get something slightly different or um that isn't kind of encompassed with the responses that we've had so far? No, OK, so I think we have an excellent foundation then, um, so what I'm gonna do is instead of giving you the response because I hope that the response will be clear to you as we, uh, talk about evolution in more detail. I'm gonna actually back up a little bit and talking again about the importance of history and when ideas kind of came about and then how sort of there's this almost evolution of thought and how there was a challenging view um and uh basically how. How the scientific community eventually adopted that new challenging view so um when it comes to the way we think about how organisms or or where do they come from essentially one of the prevailing paradigms um for quite some time of uh human evolution, um, would be considered special creation which is also uh another uh synonym for that is natural theology. And actually there's uh a lot of evolutionary biologists, um, and in Darwin's time at least, Darwin was very uh influenced and inspired by a lot of the original writing of, uh, someone who would consider themselves to be the prominent person in natural theology. So a lot of the ideas that Darwin had were inspired by the prevailing paradigm at the time. So not to say that when we switch to a different paradigm that we're sort of getting rid of all the ideas from the original one that's usually not what happens, but the claims that the special creation paradigm were stating uh the testable claims would be that all species were created separately and therefore are unrelated to one another. That each species is unchanging and there is little variation within each. Species being a distinct identifiable type of organism, we're gonna talk a lot more about species in week 4. But just a quick definition. OK. So those are two claims really important that you are familiar with those claims. Again, they're testable statements because we can go and verify them. So then there were some challenges to that prevailing paradigm and they came about in very different ways from different people, um, one in particular, a group of individuals, the early paleontologists such as Mary Anning, um, so this would be like the end of the 1800s, mid 1800s or end of 1700s, mid 1800s. Discovered fossils for life forms that no longer existed so for organisms that um no one had ever seen before. So of course that would sort of go against the claim that species um basically if species could go extinct, it was met with a lot of resistance because why would they be created if they're just gonna be snuffed out essentially. Um, actually this book that I've put, um, a link to on A2L, it's, it is a I guess a historical fiction, so there's definitely a lot of the details aren't completely historically accurate, but nonetheless it it does talk about Mary Anning and sort of her um influence in in the field of paleontology, and it's a really fun read if you haven't read it already. OK, so skipping ahead a few years after Mary Anning, so this is 1858, Charles Darwin and Alfred Russell Wallace made two claims regarding the natural world that almost stand in complete opposition to that the prevailing paradigm at the time. They made the claim that species are related by common ancestry, so they're not completely separate, distinct, unrelated. They're all related through common ancestry. And that characteristics of species can be modified from generation to generation, and this is also known as descent with modification so that means there are changes um within species that can happen over time which um one individual over here presented as one of the definitions of evolution. OK. So, so these are again testable claims, right? Things that you can go out and make some observations and see whether these claims are validated or not and how do they compare to the prevailing paradigm at the time. So when we talk about species changing over time we often think of that in terms of microevolution, uh, which we're gonna spend uh all of next week really delving into whereas when we talk about species splitting and diverging, that's often referred to as macroevolution so that's when we get into the concept of speciation, um, and we'll talk about that in the 3rd week. Um, so just a couple of definitions off the top of, of, uh, the bat, um, where we will be talking more about each in the coming weeks. OK, so then what is evolution? So this is the definition that we're going to use for the purposes of the course, although I, I, I believe that you all presented a a nice um eloquent definition of it as well. So it's a change in the characteristics of a population over time. It means that species are related to one another and can change through time so there is a secondary part to this that common ancestry is sort of critical for evolution to be true, um, and that it suggests that species are changing over time so species forming populations and within the populations those characteristics are changing from one generation to the next. OK well we we have population in the definition so we have to make sure we know what uh uh the definition of population is um so it is a group of individuals of the same species living in the same area at the same time that's a really good definition to be familiar with. OK, so how does evolution occur? So we're talking about this sort of, you know, theoretical concept, but what is the mechanism of evolution? And there are several, um, but you can kind of categorize them into adaptive mechanisms uh one of the students mentioned adaptation, um, so there could be adaptive uh methods and, and we also refer to this as selection, um, chapter 20.4 of the textbook, um, focuses on selection and we will talk a lot about that next week. But then I want to uh present right off the top of the bat that there are non-adaptive mechanisms that are just as or in some instances more important for generating evolution. So genetic drift, gene flow, mutation, non-random mating, and we'll get into all of those mechanisms in chapter 20.5. So that'll be in a couple of weeks' time. But let's just start talking about uh um adaptive forms of uh evolution because that is where Darwin comes back. So linking back to Darwin and Wallace. So Darham wasn't the first to challenge the idea that species were unchanging, but he was the first to amass a huge amount of data or evidence to back it up. So it wasn't even just based on a single observation, but many, many observations that he had the luxury of going out onto a boat for years at a time, um, and actually, um, you know, looking at different species and characterizing them. So together with Wallace, um, Darwin and Wallace proposed the most famous mode of evolution, natural selection. Again, it's not the only mode, but it's the one that we're gonna spend a lot of time on. OK, so we're gonna talk about two conditions in which natural selection, um, it is contingent on. So these must be met for natural selection to occur in a population. The first is that individuals must vary in traits that are heritable so that the characteristics can be passed on. So the information, the DNA that gives rise to those characteristics must be able to be passed on from generation to generation. So there is some sort of genetic basis. For the traits that we're talking about, so that's the first rule, or condition. The second is that in a particular environment certain versions of those heritable traits help individuals reproduce more than other versions. So I think actually a student already alluded to this, so it's. You know, natural selection and when we talk about fitness it's not about being the biggest and strongest it's about the fit of a trait to a particular environment and environments change, right? So, so in a particular environment it's the heritable variations and traits that actually help individuals reproduce more than others um and those are the ones that are gonna be more likely to be passed on from one generation to the next. OK, so these are gonna be critical, um, to be able to, for example, if I were to give you a scenario with some information, um, and I asked you is, is, uh, there evidence of natural selection, you should be able to think through the two conditions that are met and see whether there's enough information to address that. OK, so a couple of more points here. So if certain heritable traits lead to increased success in producing offspring, then these traits become more common in the population over time. So think about it this way if there's only individuals that have, let's say, um, large feet, I'm totally making this up, large feet, um, in a particular environment it was those individuals that were able to produce more offspring contributing offspring to the next generation, those uh. Offspring are gonna be more likely to also have large feet because they inherited um the traits from their parents. OK, so it's really occurring on the population scale. It's the proportion of individuals in the population that is changing from one generation to the next. So rather than it being at the individual level scale, we could think of many, many traits that change at an individual level scale. My hair color gets a little bit lighter in the summer, for example, or we grow or you know, there's other sorts of things that might happen at the individual level, but that in and of itself is not evolution, um, whereas changes that occur at a population scale, the proportion of individuals with particular traits that changes from one generation to the next and that would be considered evolution. Natural selection acts on individuals because individuals that have those traits are either benefited more by them or less, whereas evolutionary change occurs in populations. This, I think I just remembering back all the way to when I was an undergrad was a distinction that took a while for me to get. Some of you might already be there, um, but thinking about evolution occurring on a population scale versus individual scale took me a little bit of time to grapple with. So if you're also kind of in the same boat, I'm really hoping that we're gonna set up a lot of different examples, making the distinction between these things so that it becomes more and more clear. The last point is that speciation occurs when populations diverge to form new species, um, so what we're gonna be really focused on is sort of the steps before speciation, um, and then we're going to talk more about speciation in in a few weeks' time. OK, couple of other important definitions. So fitness, it's the ability of an individual to produce offspring, and individuals with high fitness produce many surviving offspring, whereas those with low fitness produce fewer surviving offspring. Adaptation, very important definition. It's a heritable trait, so it has some genetic basis that increases the fitness of an individual in a particular environment. So I'm taking the time to verbalize these definitions because they're gonna be extremely important. OK. So the next, uh, sort of, uh, example I'm gonna go through is setting up sort of a scenario and then we get to think about whether we have evidence of natural selection occurring or whether there's an adaptation involved. So before I get into that, I just want to pause for a quick second to check in with everyone about the definitions I presented. Is there anything that you just have a sort of a quick question about, um, or want me to clarify before we get into the example? No. OK. OK, so the example that I'm gonna start with, um, is one of the more famous ones from Darwin's notes when he was, um, sort of traveling around and stared at a bunch of organisms, finches being one group. So the finch is on the Galapagos Islands. Um, one thing that he observed was that there's quite a bit of variation in beak size and shape, and this image here just kind of shows you visually what that looks like. So some of these with really sort of almost shorter like more stout beaks, more robust, others with longer pointier beaks. You also noticed that when rainfall became consistent, so when there was constant rainfall, that small soft seeds became more abundant in the environment. So there was this change in the environmental conditions such that the food type of the birds that was available was predominantly these small soft seeds. OK, so environmental change, uh, paired with standing variation, we already had variation in beak shape. What happened as a result of this consistent rainfall was that there was this observed shift in the proportion of finches in the population with small pointed beaks, OK, so maybe before there would have been like, I don't know 60% of the population. Had a different beak type maybe 40 had the small uh pointed beak, but then after this long period of rainfall, when you check to see how many individuals had small, uh, pointed beaks, it was a greater proportion, so something like went up to 60 or 70%. So the question I want to ask you, and you have to think back to the two conditions of natural selection, is whether small or pointed beaks are an adaptation to prolonged rainfall. How would you be able to test this? So think about what you'd have to verify or validate in order to say that this uh small pointed beak, um, is an adaptation to rainfall. I'll give you a couple of seconds. You could either jot it down or just quickly chat, um, and then we'll take it up as a group. All right. So I'm gonna check in. So what were some uh responses that you got to

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this question? Anyone on this side. Yep. And Oh, that's that's an excellent um sort of way

SPEAKER 1

of testing that question. So just to reiterate it's also so I'm picking it up on the uh recording so the idea was to look to see um the same species of fish but in different geographical locations where you might have more or less rainfall to see whether that same trend occurs where you get the more individuals with small. Pointed beaks when there's consistent rainfall is that capturing what you said? Awesome. And if that were to be found across a bunch of different regions, it, it probably would be, you know, good support that, um, small pointed beaks might be an adaptation. What are some other, uh, things that we want to verify? Yep, movement as well so that distinct and you could really observe. So really defining where the population is, right? is that what you're kind of getting at, um, and so being able to delineate sort of where the populations are moving and how they're interacting with the environment, is that kind of capturing that that would be important for sure, yeah. Yeah, so you'd actually have to make sure that the proportion has increased, um, after the rainfall. Absolutely, yep. So you'd have to satisfy one of the two conditions. This is what I believe you're saying, where you have to be able to see that the individuals with that trait are actually surviving and reproducing more than the ones that aren't. So there has to be some sort of fitness advantage to possessing that trait. Awesome. There's one other condition that we would also need to validate in order to say that small pointed beaks were an adaptation. Is anyone, uh, yep. It has to be heritable. So there, so for example, like so the proportion of individuals might have small pointed beaks, but if it's not heritable, none of the offspring of those individuals are likely to have small pointed beaks so there will be some sort of random number, but you won't see that proportion going up. So there has to be some sort of heritable basis, some sort of. Which we would now call genetic basis because we understand the mechanism. There has to be some genetic basis that gives rise to small pointed beaks as well. Those would be the two conditions fitness and heritability. Awesome, so we're gonna, uh, stop it there for today, um, and then we'll pick it up on Friday and we'll get into an activity.

SPEAKER 0

You Uh, when you talk about like natural selection, the trait become more common in the population over time, it doesn't have to do with like the parents of the. The how they because they have the trait they're able to reproduce more either because of the environment or I know like we like peacock the. like a. It's more Latinos that one way they're most likely to. In terms of meeting the That would be an example actually you would call that sexual. OK, and what you like. how many generations of that has to be there. That's such a good question and something that will get to mathematic. Evolution, or sorry, sometimes natural section lead to evolutionary change in a single generation. Sometimes, sometimes it takes many, many generations. So you said to uh think about the question about. Oh, you told us to think about the about biology. Yeah. So I guess how much.

SPEAKER 1

So I'm assuming first of all that maybe some students have taken that course, but it's not. So yeah, so any of the material that I'm presenting in lecture, for example, to see like that would all

SPEAKER 0

be like legit to ask a question about, but none of the actual information. We. Yeah.

SPEAKER 1

Perfect. Yeah, anything in the orange boxes, extra resources, that's for

SPEAKER 0

personal. Where are you? You know it's just heart rhythm rhythm, it might take me a few. It's something that we're gonna go back. It essentially are we getting at the fact that. Like

SPEAKER 0

All right. So we could get started. OK, so. Just to reorient ourselves um with what we've been talking about this week and we're gonna finish off um continuing to talk about evolution. Um, and again this is a really broad overview of evolution and subsequent weeks will start to, uh, pick it apart into its different components. But hopefully what I want to spend most of the time doing today is setting up an experiment, so to speak, where you have to think through the best way to first of all, formulate a hypothesis, um, how you would go about testing that hypothesis, thinking about the principles of experimental design. I'll introduce, um, and then pitching your idea, um, hopefully to the group today, um, or if not at least writing it down so you can kind of think through the logic that it took to get to that step. This is very likely to be a short answer type question on your test one, just a big hint. Um, so going through this process is really gonna help you, the more practice you get doing it now, it won't be such a surprise going into it in test one. OK. So yesterday, no, 2 days ago we were talking about uh the Galapagos finches and in particular the question of whether the small pointed beaks were an adaptation to persistent rainfall and we talked about whether that was true or not, but what we would actually need to do or what data we would have to have on hand to support that this was an adaptation. So one of the sort of themes that came through is that first of all, you would have to find that finches with small pointed beaks had higher fitness. So that they were producing more offsprings, and that Small beak size was heritable. OK. So those were the two conditions necessary and sufficient to say that small pointed beaks under this particular environmental condition was an adaptation. OK, so a higher proportion of of uh individuals in the population would have results when these two things come into play. So small pointed beaks can be considered an adaptation that increases the finch's ability to thrive. And if these were to be true, what you'd expect to see in subsequent generations is that the frequency of finches with small pointed beaks would increase. OK. OK, I'm gonna provide another example because I want us to really start thinking about what. It means when we are trying to define traits, traits that could potentially be adaptations. Um, and so in this example, I'm just gonna talk a little bit about um the water fleet or Daphnea, which is a powerful model system for studying a lot of ecological and evolutionary questions among others. Um, but imagine that you for whatever reason, uh, were really interested in Daphnea, um, and you went out to different lakes and you were sort of looking at the morphology, um, of these little, um, organisms. So let's imagine that Lake A, um, you notice that the Daphne sort of look like what you see on the left here, OK? And you also notice that in this particular lake, there are no natural predators of the Daphnea. Now let's say you were to go to another lake, uh, Lake B, and you saw that a large proportion of individuals in that lake produced or or looked like they um had the spine sort of uh projections coming from their frontal um uh from their head region and in this case predators were present. OK, so those are your observations. Now let's kind of walk through the same question that we did before our spines, the presence of spines and adaptation, um, in terms of uh when predators are present, so maybe there's some sort of anti-predator response or some sort of defense response. So how would you go about, first of all, addressing what criteria would you need? What two conditions would you need to suggest that spines are an adaptation? Uh, yep.

SPEAKER 1

You can observe the ratio of baseline not like to see if that's minus uh.

SPEAKER 0

So you first want to determine whether spines themselves, the presence of spines are heritable. So there is some sort of genetic basis for having spines or not. Awesome. That is one. Yeah. Is there another one that we would have to show? Yeah. Yeah, so, uh, for what particular individuals what. Sorry? So what ones in the population would you expect to be able to produce more offspring? Yeah, so you'd have to see some some sort of positive correlation between the individuals that have spines and then the number of offspring that they produce such that there's differential reproductive success. So so so those in the population that don't have spines are not going to be, I need to put this somewhere else, are not going to be as um fit or uh produce as many offspring. OK. So one thing that is interesting about this particular example is that if you were to spend a little bit more time at either lake, you notice that predators can kind of come and go seasonally um within the the uh life span of a single Daphne, let's say. And you're actually noticing that if you track individuals, for example, if you were to track this individual, um, and you notice that as predators sort of entered into the environment through whatever mechanism, that that individual started to produce spines. OK. So, what we consider the presence of spines in that case to be an adaptation? Why or why not? So who would say that you would still say, so even though individuals within their lifetime can gain that trait, um, would you say that the presence of spines in and of themselves is an adaptation? Uh, who would say yes to that? And who would say no. And anyone from the no group would, uh, be brave enough to just give a little bit of a justification for that. Yep Yeah, so because this was kind of a trait, let's imagine, um, you know, I don't know if anyone goes to the gym, but you go to the gym and maybe you check your muscle mass, um, before you really start going, um, and then over time you you start to build a bit of muscle. So you wouldn't expect then if you were to just reproduce and have kids that those babies would be also quite muscle. right? So it's the same thing where in this for this particular trait, it's not necessarily the presence of spines, but the underlying ability to produce spines in the presence of predators. And so when we see changes in the outward appearance of organisms, it's not just due to genetic factors, it's due to genetic Genetic factors combined with environmental factors that give us that outward appearance and in many cases the genotype of individuals doesn't change but under different environmental conditions we can actually see changes in particular traits. Does anyone know the term that we use to to talk about sort of phenotypic changes without a change in genotype? Yep. Epigenetics that that could be a mechanism that underlying the term that I'm looking for. Yep. Close. I'll give maybe one more try. Anyone else? So we refer to that as plasticity so the idea that there could be a change in the outward appearance, not due to changes in the genotype of the individual, but due to often environmental triggers that perhaps change sort of the expression of those traits, OK? So the whole point I'm trying to impress upon you here is that the whole process we went through to determine whether spines. Themselves were adaptations or not, it wouldn't matter if spines is just a you know a fixed trait so organisms produce them or not or whether it's the propensity to produce spines under a particular environmental condition we would still need to establish that it is a heritable trait, so the ability to induce spines with the presence of predators plus that the individuals that have that ability are able to produce. Or offspring those two still have to be met in order to say that spines are an adaptation. In this case we would say that the propensity to um to develop spines rather than spines themselves. It's not the specific trait that's fixed in this case um, Daphne are able to actually induce spine formation or development. So it's just a little bit of of a of a nuanced example. Yep. Do you have a question? So your question is, wouldn't we still need to see differences in the two environments to say that they're an adaptation? Is that what you said? So it would, the two lakes would have to have a similar environment and then the ones that are actually producing the adaptation or the the spines in this case. Yeah, so you would still have to see within each lake that there's some standing variation in the ability of Daphnea to produce spines or not because you still need to. That relationship between fitness and the trait itself so there's gonna be some individuals that are not as great as at developing spines, um, and other ones that are and the ones that are the ones that would go on to survive and reproduce and pass on that ability to offspring. Does that satisfy the question or? I OK. Awesome. So Uh, oh, and also because of how interesting Daphne are and sort of this developmental mechanism, um, I've added a link to the um A2L that talks about Daphne in a little bit more detail if you're interested. OK, so really quick recap. So we have been talking about one of the three fundamental theorems or theory in biology, life evolves. So the theory of evolution states that all organisms are related by common ancestry, and that natural selection being one mode of evolution, but not the only, um, it's a well-tested explanation for why species change through time and why they are so well adapted to their habits habitats. OK. So the whole last part of this section, um, I want to give us a lot of time to go through an exercise of how we actually go about testing hypotheses. So of course, scientists, the reason why we kind of do what we do oftentimes is because we're very curiosity driven or because we're trying to solve problems that actually impact society. So we're asking questions and we don't want just a response based on our, you know. Conceived ideas of how the world works. We want to be able to falsify our statements. So we have to measure things and collect data and ensure that the data being collected as unbiasedly as possible can tell us whether our statement about how the world works is valid or not or supported. So the whole process is about coming up with sort of a guess as to how things are working, a hypothesis, and then finding evidence or I should rephrase that by saying by collecting evidence that would then either support or conflict with the hypothesis that you're presenting. So for example, we can carefully design experiments to test ideas about how the natural world works. Um, testing, so looking to see at the outcomes of our experiments, whether, um, the hypothesis is supported or not, and in which direction. It's important to note that of course we don't have to do just you know manipulative experiments to get to this we can also look sort of at natural variation in different um environments rather than manipulating anything but the example that I'm gonna kind of walk you through today is when we do some sort of a manipulative experiment we're changing a specific factor that we think might be important for determining fitness, for for example. So I want you to highlight this in your notes because this is gonna be really important when it comes to um speaking about how to set up a really strong experiment. So a well-designed experiment, it includes one or more control groups to check for factors that might influence the outcome. OK, so we, for example, maybe only care about let's let's come up with an example of light and we want to know how the impact of light affects plant growth, OK? When we go and set up our experiment, there's gonna be so many other environmental parameters that could potentially also impact plant growth, right? The temperature, the humidity, um, how much water the plants are getting other nutrients. So we want to control as much. Is possible for all of those other factors that we're not interested in for this particular experiment so that we can isolate the factor that we are so all those other factors you can also refer to them as confounding factors whereas the one that we're interested in or in some cases several that were interested would be sort of the um focal um manipulations or factors that we care about. So we do need to have some sort of mechanism to control for all those confounding factors. And oftentimes we can use control groups to do that. We also need to think about, um, experimental conditions, um, in which, again, so for example, let's imagine you're planting your plants in different places in a field. Some of those that the plants are actually gonna be closer to um a I don't know, a brook or something that has running water and other plants don't aren't exposed to that. So if you decided to set up your experiment in such a way that you know the ones that one section are experiencing higher light plus also are closer to that water and then on the other section lower light lower water. Now you have a confounding factor, so you can't actually say whether plant growth is impacted by light itself because you have this confounding factor where there's just also lower water on the other side. So you really have to think about how you're setting up your experiment in order to make sure that you're reducing those confounding factors. And a good way to do this is to include um what we call spatial replication. There's also temporal replication. So we actually repeat our tests or we include multiple replicates to reduce the effects of distortion due to small sample size and to account for the confounding factors that are present in the environment. So there is a little bit more information in the textbook about these particular definitions, but you do want to pay attention to these as we're going through this exercise. OK. So what I'm gonna do now is I'm going to play a video. In this particular context, you don't have to memorize the details that are the facts that the video is going to show you. But what you do want to do is jot down some of the traits, so some of, you know, morphological, behavioral, theological traits that you notice um that you think potentially might be of interest.

SPEAKER 2

Here we will learn true facts about the angle of fish. The female angular fish comes in many shapes, colors, and shades of ugly. It's like a rainbow of ugly. The male anglerfish is tiny by comparison, like a tiny little baby. He attaches himself to the female by biting her and then digesting part of his face so he fuses with her flesh. He then atrophies, losing his digestive organs, brain, heart, and eyes, and winds up nothing more than a pair of gonads, which release sperm when needed. Hey there, pretty lady, nice gonads to the female anglerfish, the human male is a very loud, annoying and unnecessarily complicated pair of gonads. The anglerfish is a master of disguise hiding itself among the sand and rocks of the ocean floor. Here an anglerfish compares its camouflaging skills with that of a flounder. Also a master. Holy crap, did you, what the fuck to hunt the anglerfish waves things in front of its mouth that its prey is attracted to. Here the anglerfish waves a lovely pashmina shawl, just the size for an unsuspecting shrimp. Here another one presents a lovely pair of leggings. And here a decorative hat feather. Sadly, the shrimps and their vanity pay the ultimate price. Death. The deep sea anglerfish collects glowy, glowy bacteria in its wavy thing to create a tiny little light because it's dark as hell down there and someone needs to light up that pretty, pretty lady.

SPEAKER 0

OK. so I think. You would have had a few options there to write down some interesting traits. Anyone want to kind of like list off your favorite trait yet? The camouflage, awesome. Any others? Yup. The males being tiny, yup. Any others? Yup. Predator. It's like sort of, um, yeah, so it tends to have more of like a predator lifestyle. Is that right? Awesome. Uh, anyone who, what about, uh, there we go, yeah. To attract prey, yeah, so they have, so it's called the angler fish. Angler, I guess is another word for like fisher fisher person, fisherman or woman, um, and so it uses that sort of, um, antennae as you suggested, or lure as a way to lure and prey. And and there are different species of anglerfish and each has sort of a very different lure in terms of the way it looks like and it's really interesting because the lure is often like one of the more abundant prey species in that environment. So the fact that this is independently evolved um is fairly interesting. Any other uh adaptations that we noticed, I'll go back to you. The cilia. Oh, the fins, yeah, so maybe their uh fin morphology, um, enables them to swim in a particular way. Awesome. Yeah OK. So they are kind of swimming at an angle and and that could have something to do with their um ability to kind of like maybe look below them or something like that to observe prey awesome. I'll I'll also add my favorite traits to the mix is the bacteria so they actually have a symbiosis or an intimate interaction with bacteria where bacteria will colonize this is the deep sea anglerfish, they colonize the um lure in this case. Um, and they are, uh, luminescent, so the, the bacteria are the ones that are producing the light, um, and then that actually will help the, uh, anglerfish in various ways which I'm not going to, um, talk about because you are gonna have to potentially come up with some ways in which they'll help the angular fish because that is the next part of this. So let's get into the activity. OK. So what I'd like you to do is to form groups or you're also welcome to work individually, whatever you prefer, to answer the following questions. Pick one trait that you think could be an adaptation. Make sure that you have the criteria for adaptation somewhere next to you so you can, you know, we, we're using a very specific definition of adaptation here. Formulate a hypothesis using X affects Y. So for example, what factor would you like to test would be X, and then what would you measure would be Y. And then what's null? I'm gonna give you a little bit of a hint here. So X has to be the adaptation. So some adaptation that you have come up with either as a group or individual to focus on. And then Y has to be some proxy of fitness. Fitness, again, the ability to survive or reproduce. There are so many different proxies that we could measure for that. So I want you to just pick one. A specific one. That you can measure in an experiment. Um, after you have your hypothesis, I want you to state the null. And then I want you to take some time to uh write out how you would actually test your hypothesis and paying attention to what kind of approach would you use so for example observational maybe you're just looking at sort of the natural variation in a population um or you're doing some sort of manipulative experiment. You can choose either of those. Um, think about things such as, especially if you're doing a manipulation, you will have to have treatment versus control groups. If you're doing something observational, you have to think of like what would be your baseline, for example, that you're gonna compare. Think about the concept of randomization so I didn't get into this yet too much, but basically when I was setting up that sort of um hypothetical field um experiment, if we had again all of our plants that were gonna be um subjected to highlight in one area and all of the ones subjected to low light in another area and there's other factors that are also different between those then we. Can't actually say whether light is the thing that's impacting growth or not. So one way to get around that is to completely randomize our uh replicates with respect to the treatment conditions. So we have just as many um ones that are exposed to light over here as over there so that we're minimizing the impacts of other confounding factors, OK? So that's what we mean by randomization is with respect to the treatment condition. To ensure that all of the other types of uh confounding factors are minimized in the experiment or accounted for, does that make sense? or did you, did anyone want to talk about that a little bit more? No? OK. And then replication. So again, the number of uh replications so for example, the number of individuals exposed to one particular treatment versus the ones in the control group, the greater that number, the more power you have in testing your hypothesis because you're gonna be able to account for a lot of other factors that aren't the variable of interest. Now experiments can be expensive, so sometimes we, we can't just, you know, say we're going to use thousands and thousands of replicates. There are constraints in terms of our ability to actually conduct the experiment, um, so you want to kind of come up with a realistic number that again allows you to increase the power of your experiment while also being practical or feasible to carry out. And then the last thing here um is what would be the potential outcomes of your experiment. OK. So we talked about predictions. So predictions are um the outcomes of the experiment if the hypothesis is valid. But there's also the null hypothesis. So if you were to have, uh, let's say 3 different outcomes of the experiment, one in which X does not affect Y, and then 2 in which X affects Y, you can actually think about, well, it could affect. Why in this way or that way, and this is what the outcomes would look like. So you can think about drawing even a graph where your X is on the X-axis and your Y is on the Y axis and think about what your results would look like um if there's a particular outcome that is shown. So if the hypothesis is valid, then what could be those potential outcomes if the hypothesis is not supported at all, the null hypothesis is supported, then what would the outcome look like? I know that this might right now not seem very straightforward, um, but see if as a group at least you can kind of come up with um you know what those outcomes would look like. All right, so it is, uh, we have a good, uh, 25 minutes or so. So I'm gonna give you 10 minutes to answer these questions, see if you can come up with a way of testing this, and then write out your, um, outcomes, um, and then we'll try to go through some examples as a group after that. Hey, what's up?

SPEAKER 1

Confused this question like what's the null and confused the

SPEAKER 0

null hypothesis. So if you go back to our last lecture or it might have been even the first one, I gave the Definition of a null hypothesis. I think it's when we had so we had prediction versus hypothesis and then the null.

SPEAKER 1

So it's just like Yeah, yeah.

SPEAKER 3

Hello. I just to get my mind some of the ideas. So a few different things I came up with with one is about the camouflage ability. I, I just want to clarify the camouflage effectiveness. Would that be enough as an X because I feel like we need some sort of way to quantify that. And I said quantify by the similarity and coloration and the texture in this environment, would that be? Yeah, that sounds good. And my idea would be to have control. One would be in deep darkness or rocky areas because I did some research and that is where the camouflage works best and their least effective is in shallow, well lit waters or colorful coral reefs, and the group would be. OK. OK. That's kind of what I was playing around with.

SPEAKER 0

Yeah, so their natural camouflage matches the contrast, OK. Shallow wellet waters. So one thing you could see, and then what's your why again why would be. So what happens if in these environments there happens to be more predators around in general?

SPEAKER 3

How would you wouldn't be doing observation we doing it in like a lab setting, I guess.

SPEAKER 0

OK, so then you would, for example, how would you control that between the two?

SPEAKER 3

Then we would, so in the, in Group one we would have a setting where we have, I guess, more of the, the coral reefs that it's more used to being like in the more in the environment that's more useless so it's able to camouflage pretty well or in the group two, we would have a, I guess a tank that has more colorful co reefs and making it more difficult to camouflage.

SPEAKER 0

Yeah. In terms of the predators.

SPEAKER 3

How it yeah. What I think we would have a fixed amount of credits.

SPEAKER 0

That makes a lot of sense.

SPEAKER 3

You Camp. Is this what you're talking about the positive, negative, or neutral, or no? OK.

SPEAKER 0

And you could, if you want to try, did you try to also write it out?

SPEAKER 3

OK. With the graphs, did you, did I do 3 separate graphs talking about the positive outcome, I would see like an increase, and the most would be the one that has better camouflage. The one in group 1 and then negative would be -1 with group 1 being the least effective and no significant would be like.

SPEAKER 0

So your X-axis would be labeled as.

SPEAKER 3

So that that would be the camouflage effectiveness.

SPEAKER 0

Yeah, awesome. That was one another.

SPEAKER 3

I, I did this one, but now after hearing the lesson, I don't know if it still works. It was uh the Anglo strategy of waving the bioluminous lure, with the movement pattern of the lure, would that be considered a a heritable trait like an adaption because that's the way it moving.

SPEAKER 0

Could potentially be is. It would be a trait, right, but it could potentially be an adaptation.

SPEAKER 3

Like, wouldn't, it wouldn't be a positive because. Harder to attract the prey because it would actually look like. Something dangerous than slowly. Yeah as well. Of these two either this one or the camouflage the camouflage is a stronger one.

SPEAKER 0

Yeah, I think both could work. Um, yeah, yeah, no, you're definitely on the right track. Yeah, awesome. So I'll give you a couple of more minutes, so try to wrap up now.

SPEAKER 3

All right.

SPEAKER 0

Coming back. So How about we start, um, maybe if if groups are kind of comfortable going through all three questions at a time and then we can kind of go from group to group, I think it would work that way. So who would be willing to volunteer what you came up with? Yep.

SPEAKER 1

Uh, right, so my hypothesis would be if flowing so we use blowing like at the. with that.

SPEAKER 0

Glowing light as the adaptation, yep.

SPEAKER 1

And we have the uh if the glowing light is an application, then the ratio of the. flowing That with those Would increase by glowing light over time.

SPEAKER 0

So you're saying that the proportion of individuals that produce glowing light would increase over time. Is there, so what are you measuring specifically there?

SPEAKER 1

Uh, so we just try to see if over a long period. Those with low so what I was thinking. We And we'll see the ratio, which is the why would increase our.

SPEAKER 0

So X would be time, Y would be related to fitness, which would be the proportion of individuals. So one thing about X is that what you're trying to do is, and I think your adaptation is the the glowing light, right? So in that case, you would want X to have to be somewhat related to light itself. So If I could sort of reformulate a little bit if you will, um, let's imagine that there's some variation in the population where some individuals are tend to produce more light than others, then the brightness of light or some something that you can actually measure and characterize could be on the X axis. And then the proportion of individuals surviving to the next generation um maybe that the way to capture that is survival rate so looking at the survival rate of different individuals so for example how well like did the individuals that had uh lower light survive um yes or no and then that would be survivor survivability or um survival rate would be on the Y axis. And that would relate to fitness. OK, awesome. That's a good setup. So then how would you go about, um, so first of all, so this, so how would you formulate your hypothesis in the XFXY formula?

SPEAKER 1

So according. What Or I hear so. If the flowing light is an adaptation. Then the survival, right, so, OK, so if higher light intensity is an adaptation, then the. Survival rate of angel fish with higher intensity of light will be higher.

SPEAKER 0

So you're combining a hypothesis and a prediction which is totally fine and actually there are um many for example papers that will do that but for this particular um course I just you just wanna provide the hypothesis so I think even if you're. X is light amount or light intensity, and your Y is survivorability and just take the X affects Y. So light intensity of the lure affects the individual's ability to survive. That would be the proper formula. It's not to say that a if then statement is not valid in terms of hypothesis because many people do, uh, formulate their hypothesis that way, but in terms of this course we just wanna keep it as simple as possible so XXs Y. Awesome. OK, I'm gonna try to get some other examples before we get into like how we would actually test this. So any other groups? I know there's I'll go over here on this side, yeah. Size of the antenna, yep. So larger, uh, larger praises would be attracted to larger. OK. OK. OK. Yeah Uh Exes and tennis size Yeah Yep. Yeah. A little bit more specific about fitness because again so we could measure fitness such as um the number of prey caught or the number of mates mating attempts or or directly the number of offspring or just be a little bit more specific about that metric so what is you said survival rate, right?

SPEAKER 1

Yeah. Thank So that's what you're measuring.

SPEAKER 0

So that's your why. So prey consumption or prey attraction. Awesome. Yeah, so in that case if you're gonna reformulate XX it would be. Yeah, so the, uh, antenna size, um, the size of the antennas, uh, the individual's ability to catch prey or how many preys are attracted. That would be a testable statement. Awesome. Um, any other examples over here? Yeah. OK.

SPEAKER 1

we were thinking. The Oh you don't like Yeah. Uh Yeah. But why would the.

SPEAKER 0

The survival survivability, OK. Yeah. Awesome, yeah, super clear. Um, I mean there could be other proxies of fitness. So for example, does it allow them to capture more prey because they're hiding or avoid predators. So you could have like I think survivability will totally work, but you could also have included something like yeah the number of prey caught or uh a number of uh. Predators that didn't catch, you know what I'm saying? Um, so those would be valid as well. Yeah. OK, let's go through one more example. Um, I'll just make sure given us enough time here. OK, actually, so I just to make sure we have time to go through the next part of this, um. In terms of approaches, so. I think I've heard a little bit from some groups about how they would go about setting this up, but maybe um new groups, um, just quickly introduce your adaptation and how you would go about setting it up, yeah. Yeah. OK. OK. OK, so just to reiterate, I think just also I'm capturing on the recording so you're saying that you're gonna manipulate the environment um and you're so you're gonna have an environment that has, um, sorry, a little bit more complexity and and like places where they could camouflage and then the other one would be sparser um not as many places to where camouflage would be um. I mean they just keep camouflage less but then you also have two groups within those one being the ones that have been scored more highly for camouflage and then the others that have been scored, um, less for camouflage. OK, and so in that case they're both in the both of the um environments so you can partition survivability just from the environment alone versus. It's ability to camouflage plus the environment is impacting survivability. Did I kind of capture that correctly? Awesome. Yeah, so you're already starting to think about minimizing confounding factors and um increasing replication. So I don't know if you had like 10 individuals per tank in each treatment group, you're able to get multiple measures and you can have like sort of a more robust way of testing the hypothesis. I think we have time to go through, uh, one more. So from another group to talk a little bit about how you set it up, um, I'll go over here, yeah. Yeah. Yeah. Can I pause for a second? Just I want to recapitulate what you're saying. So you the adaptation is the brightness of the lure, the uh fitness component is how many a prey their ability to catch. Then you have two tanks and you're manipulating the amount of bacteria. In one case, there there are more bacteria that are able to colonize, so it increases the brightness, and in the other there's fewer bacteria. Is that correct? OK. Yeah OK, so 3 different treatment groups, one with a lot, one with fewer, and then one with none. And so basically if you then see that they're able to catch more under the, for example, more bacteria condition because there's greater brightness than they would support your hypothesis. Awesome. OK, I guess let's just check in. We do have a minute or so, so just to make sure again, this is gonna be really important when it comes to testing. So what I've done is I've also included another example which actually kind of overlaps with some of the things you were talking about. Just make sure you're going through um in terms of. You know how you would set this up minimizing any confounding factors you're including replication, randomization, those are the key terms we're using in the rubric to grade this this question. So make sure you're paying attention to those any questions we can talk about it next week or post on Teams. Thank you. Uh, I'm still waiting on my grad TA schedule, so I should post it hopefully next week. Yeah, no worries. OK.