energy is an essential ingredient for life. In fact, it's so important. There's a whole field of study dedicated to examining how energy moves through living systems and especially looking at how energy flow is related to an animal size and its metabolism. Now metabolism is through the some of the chemical processes of an organism that sustain its life. A great example of one of these processes is cellular respiration, which is, of course, the process. Oops process by which, uh, cells will break down carbohydrates from proteins, sugars and fats and convert it into energy in the form of ATP. Through that amazing process known as oxidative phosphor relation, go check out the videos on cellular respiration. If you want a refresher, want to Nome or about this process. Now metabolism is often conceived of in terms of a metabolic rate were a rate of energy consumption, and there's different ways to measure metabolic rates. But I think this chart is super neat example of, uh, metabolic rate, a specific type that we Noah's basal metabolic rate, which is basically the minimum rate of energy consumption of an endo therm at rest. Now, basically, at rest means you know, not exerting themselves physically not stressed out. So just like, you know, chilling out, kind of like what it sounds like. They're just relax and chilling out maxing relaxing, all cool, uh, and a therm, of course, that Z organisms like us that generate our body heat from internal processes. And what's so nifty about this chart is you can see how different types of food we eat actually sustain our energy in different ways. Carbohydrates, as you can see, give us a nice initial boost of energy. But they kind of don't last right. They plummet after a while. Proteins, on the other hand, don't give us as quick on initial boost of energy, but you can see that they sustain us much longer. Right? That curve goes way above the carbohydrate curve. They provide us with more long term energy. Now, basal metabolic rate is looking at endo therms. There's another measure we know a standard metabolic rate that is the minimum rate of energy consumption. Oven ecto therm. A rest and an echo therm, you may recall, is an organism that absorbs most of their body heat from an external source. It doesn't mean they can't generate any heat internally. It's just that, uh, their main source of it is coming from outside. Now, when you start comparing metabolisms of different animals, some really cool patterns come out. One of the more obvious ones is that warm blooded organisms are going to have higher metabolic rates, fan cold blooded organisms. And hopefully that comes as no surprise, warm blooded organisms. And you know, these terms warm blooded, cold blooded, very imprecise, kind of like common terms we throw around, we'll talk about technicalities and of all of that in a different lesson. So don't stress now. It's just, you know, warm blooded, cold blooded. You know, uh, you know, we can think of this in layman's terms for the sake of the explanation. So anyways, warmblooded organisms have to consume energy. Thio warm their bodies, whereas cold blooded organisms are going to be again absorbing. Most, uh, are going to be, um, well absorbing heat for their bodies, but also not expending a ton of energy to warm their bodies. There's others, uh, sort of strategies in there, too. But the main point is that these guys are consuming energy and therefore adding to their metabolic rate in order to heat themselves, and these guys aren't so much. And hopefully it comes as no surprise that uni cellular organisms which, of course they're very simplistic, have smaller energy requirements than these multi cellular organisms and therefore will have even lower metabolic rates. That's what these lines are showing us the metabolic rate increase of these particular types of organisms. Now, a really interesting pattern to note comes out when you compare larger animals and smaller animals. So looking at an elephant and a mouse, obviously obviously the elephants is far larger than a mouse. And in terms of, you know, total like tonnage of energy, sheer quantity of energy, they need more, obviously, right that they're much bigger organisms. They have much larger muscles that need to be powered. So of course, they're going to require more energy, then a little mouse. Here's the thing when you look at their metabolic rates compared to their body size, though, so essentially you find the relative metabolic rate of metabolic rate. Um, you know, look sorry when you when you look at the metabolic rate relative thio the body size of the organism. What you see is that smaller animals like the mouse will actually have a larger relative metabolic rate than a larger animal like an elefant, essentially like pound for pound. The elephants metabolic rate is lower than the mouse's, and this again has to do with those patterns of surface area to volume. Right. Larger organisms are going to be less prone to heat loss, for one thing than smaller organisms. So smaller organisms we're gonna have to dedicate a greater percentage of their metabolic rate to warming themselves. Just lots of interesting patterns and things to look at. When you start delving into the comparisons between energy use of different animals. With that, let's flip the page.