Animal Physiology and Fitness Trade-Offs

by Jason Amores Sumpter
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Hi. In this video, we're going to talk about the basics of animal physiology and cover the major types of tissues found in animals. Now, anatomy is the study of an organism's physical structures. Very famous. Studying anatomy is this image here, The Vitruvian man, drawn by Leonardo da Vinci Physiology is the study of the functions of those structures. So here you can see the human cardiovascular system, which is a network of veins, arteries and capital Aries. And, of course, the heart, those air, the structures, the function. The physiology of this is to pump blood, and mainly to get oxygen to deliver oxygen to tissues in the body by pumping the blood around. So there you have that difference between anatomy and physiology. Now organisms are going to have adaptations that they acquire through evolution. These were going to be in traits that are they're able to pass down to their offspring heritable traits that will improve their chances of surviving and reproducing in their environment. One of my favorite all time examples of an adaptation is with these maws behind my head. You see, Prior to the industrial Revolution, most of this species of moth appeared like this. They were white. The industrial revolution in England brought on tons of smog and pollution and generally darkened the air and, ah, stained dark. You know, just the environment around these factories. And so over time the population of moths shifted from mostly having this white appearance to mostly having this black appearance. And the reason for that is these white mods stuck out like sore thumbs in the post industrial world, making them easy targets for predators, meaning they had a lower chance of surviving and a therefore a lower chance of effectively reproducing. So now this species of moth is mostly in this appearance, or mostly has this appearance. Now these adaptations should not be confused with acclimatization, acclimatization, zehr short term, um, basically short term adaptations to changes in the environment. These are going to be things like, uh, the amount of oxygen that your red blood cells can carry. I mean, it was the famous example. Lots of runners want to train high altitudes because the thinking is by training at high altitudes, they'll acclimatized to the high altitude and they'll their blood cells will be able thio, suck up more oxygen and therefore they will be able to deliver mawr oxygen to their tissues. The problem with this is as soon as these runners go back to normal lower altitudes, they're gonna lose this effect. It actually goes away so quickly that it's in some respects, almost not even worth the trouble. So, uh, adaptations, they're gonna be long term passed down through generations. Acclimatization happens within an individual in a short span of time. Now, the thing about evolution is it's not going to lead to perfect adaptations. There's this idea called fitness trade offs, which is essentially a limit to an organism's ability to adapt to its environment. And this is in part due to a finite energy capacity. Essentially, an organism has Onley. So many resource is it can commit, right? I really like to think about this. If you've ever played a role playing game, right, your character has different stats. You can Onley commit a certain number of stat points, though, right? You can't make your guy really, really strong and really, really fast or something, right? You only have a set number of resource is that you can allocate well. The same is true with adaptations, organisms can't make everything perfect because they only have a finite resource pool to draw from. So what you get is essentially a cost benefit compromise for the energy investment in adaptations. Basically, you want to expend the least amount of energy for the biggest effect now adaptations air also going to be limited by existing A. Leal's and ancestral genes and organisms can Onley modify or really only work with the genes that came before the genes that are available to them, So that's going to constrict the possibilities in terms of an organism's adaptations. For example, our spines are actually terribly designed for us standing upright. That's why basically all humans have back problems. The reason is we weren't intended to be upright creatures. The spine came from creatures that walked on all fours. But that was our constriction, right? Those were the confines within which we had to work. So you got to live with the back problems. Now there's also a trade off between the reproductive success of an organism and its chance of survival. You know, Uhh. The way I like to think of this is if you commit too much toe having one successful reproduction you might actually be losing out when you could have had to mildly successful reproduction periods. So I guess what I'm trying to say is, sometimes it's more important to ensure the survival of the organism so that they can reproduce another day than to just commit all the way to just getting that one reproduction done. Uh, you know, one of the ways this often comes up in terms of survival is the immune system. You know, it takes a lot of energy for animals to mount an immune response, and sometimes it's worth it to sacrifice reproduction in order to ensure the organism survives and again can reproduce another day. So, yeah, you know, basically what this all comes down to is if a mutant Lille altars of feature in an individual, and it allows that individual to survive and reproduce more efficiently that alil is going to increase in frequency in the population. This is getting back to that idea of Hardy Weinberg population genetics with the frequency of genes appearing in a population, you know, the idea is that if an individual survives and reproduces more effectively, they're going to have more offspring that have that mutiny, Lille and those offspring are going to survive and reproduce more effectively. So they're gonna pass on that Alil. So it's going to become more prevalent in the population. Now. Just it illustrate this idea of fitness tradeoffs with some real world examples. I want to talk about the Cheetah. Now, Cheetahs are known for their ability to run super, super fast. And the way this actually works is if their legs air longer. They're able to actually run faster, but they only have a finite resource pool. Right. If you make the legs too long, the bones are too brittle. The cheetah will risk breaking its legs all the time. You don't want to make the legs too short, because then it's not gonna run fast enough. So you need to find this cost benefit compromise the longest you could make the legs while the bones air still sturdy enough that the chief is not gonna risk breaking its leg every time it prints after gazelle or whatever. Another beautiful example of this also with another animal from Africa. The giraffe, as you can see here. And as I'm sure you know about drafts, they've got this really crazy long neck, and part of the reason for that is they're able to reach vegetation that's higher up than other herbivores can reach. Right? They could get. They could eat the vegetation that's in the treetops that other or other herbivores can't get to. This allows them to survive more effectively because they don't have to compete with a bunch of other organisms for food, right there, really kind of just competing with drafts. Other dudes you can reach all the way up there. Here's the problem. That neck is really big and really heavy and really energy expensive to make. So you know you could have the best neck in the world, but that's not going to be efficient. You want that cost benefit compromise. You want the neck to be just long enough that it can reach that vegetation, and the organism will easily be able to secure food we're at. At the same time. It's not going to waste tons of energy in having you know an overly long neck. I mean, just think about the amount of muscle in there alone and all the energy demands that muscle has just to keep the organisms head up. So with that, let's flip the page