Biology 1010 Lecture 1 Intro to Biology

0:00 - [Instructor] Biology, like any other discipline, studies one particular aspect and for us as far as the physical sciences go, biology is essentially the study of life. If you have physics, you're studying the laws and such that govern how all matter and energy work in the universe. If you're looking at chemistry, you're gonna study the interactions between atoms and things of that sort but life deals with essentially, how all living things, what is common amongst all living things? And so when we study life, it's one of those things that doesn't quite have an easy definition. We all intuitively know what is alive and what is not. Even a kid knows, I'm gonna pass around this dead chicken embryo but it used to be alive or it was growing and developing, I've stained it so you can see the bones and the cartilage in its limb development. But if somebody were to look at this and be like,

1:03 well, yeah, that could have been a living organism, that was alive but they look at a rock and be like, yeah, that's not gonna be alive nor was it alive or whatnot. So how do we intuitively know that these things are not alive or will never live? I mean, what is life? That's the question, we're still kind of in that gray area, we can say, oh, yeah, that's a lie, that's a lie. That's a lie but I mean, there's 10 million species on this planet alone and there's more than likely life elsewhere in our universe. I mean, it'd be ridiculous to think that there wasn't, just to the very nature of how things work. So the big question is really, how if you want to succinctly say, even to a child,

1:49 why is this rock not alive? Like the rock that's being passed around, and why is this cute little bunny rabbit alive? Living things move around and they can kind of intuitively know that but sometimes things aren't so obvious as far as what's alive and what's not. For example, when you get into zombies. They do kind of all the things that living things do. Yeah, technically, they're dead. So what makes the difference between the awesome shot that I am with the Glock at 25 feet, versus the zombies that are not alive? Now that may seem like a silly example but there's still a debate today, when it comes to things like viruses. Some scientists, even here at UVU would argue that a virus is technically a living organism and there are others that would say, no a virus is not alive. So how do we draw that line? Because the virus exhibits all of the characteristics that a living organism does, which is why there's still this debate today, as far as where you draw that line.

2:55 So the solution is as follows, so far most scientists can agree upon a particular definition of life, despite the fact that there are millions of species of organisms on our planet and millions more that have lived on our planet that are now extinct. They all share one common feature characteristic and that's where we get to our first or your first question that you're gonna have, which is cell theory and that is that all living things are made of cells. That is probably one of the most succinct definitions of life is that a living organism, whether it's a single cell, which is what we call unicellular or whether it is made up of trillions of cells like you and I, which we would call multicellular. Multicellular, it's not all organisms have that many cells. Obviously, there are worms that have like 1,000 cells but they're still multicellular. Bacteria, yeast, a group of organisms called protists

4:01 or subgroup within that kingdom. These are single-celled organisms, they're unicellular but they're still alive. They're considered living organisms because they fit within this theory, which is cell theory. Now, there's a couple of ways of describing cell theory. Here's where the different versions of your quiz questions are gonna come into play. So the first one's already shown up there. The theory that all living things are made of cells but there's a couple of other ways of describing this. So let me give you a couple of them. I could ask the basic unit of life, okay? So the smallest unit of life is a cell, that's saying the same thing, that all living things are made of cells. In fact, if you were to take cells from your skin and put them in the right environment, they would continue to grow and live, even though you remove them from your body. So cells kind of one of the most basic units that can function independently if given the right environment.

4:56 They're self-sustaining structures that can replicate and propagate or reproduce essentially. Another way of describing cell theory is that all cells come from pre-existing cells, basically cells make more of themselves. Now, this is not the same concept of evolution, where they talk about, we'll get into what evolution is and what evolution is not but this is not the concept that all living things came from single cells in the beginning, so to speak. That is not what cell theory is, okay? So all cells come from pre-existing cells, that's part of cell theory, I'm just letting you know,

5:42 sometimes people confuse and they'll choose a wrong answer, which is saying that, the first organism on life on this planet was a single cell or that all life comes from single-cell organisms. That is not cell theory. In fact, that's not exactly even what evolution is, okay? So one more concept, you could just say that the most basic level of organization 'cause we're gonna talk about organization here in just a second, the most basic level of organization of life is the cell, okay? So those are just a couple of different ways of looking at how to describe cell theory but they all encompass the same thing. All living things are made of cells, all cells come from pre-existing cells, it's the most basic unit of life.

6:31 All living things are made of cells and that's why a rock is not a living organism 'cause it's not made of cells. That's why there's this debate in viruses because viruses is not included in cell theory. Viruses are not self-contained structures that we call cells. So we're gonna look at the organization of a cell a little bit later on in chapter three, I believe, where we look at how a cell is structured? What's the dynamics of that? But we've gotta build up to that first. Now, to delve a little bit deeper and get a little not more complex but a little more detailed is there are five characteristics that every living organism exhibits, okay? So this is not necessarily the unifying theory but if we were to say what are the characteristics that all living things have in common? From the simplest of bacteria to the most complex of animal and plant species, these are the five right here. Now, that's what you're gonna be tested on for this first lecture.

7:36 In fact, this is how we're going to study biology this entire semester, is looking at each one of these characteristics. The first five or six lectures are all on how life is organized. The next few lectures are on how living things use energy. Throughout the semester, we'll be going over this concept of homeostasis. There aren't really any lectures on homeostasis, I guess you could say lecture seven is when it looks at how cells use energy to balance things with the environment and maintain an internal equilibrium but there's not really like a particular lecture. So you're gonna see this concept throughout the whole semester as far as homeostasis goes. Then later on, we're gonna look at reproduction. We're gonna look at how cells reproduce. We're gonna look at sexual reproduction. We're gonna look at genetic inheritance. This is when we get into diversity and looking at how we propagate our species and how other species replicate themselves.

8:37 This is where we're also gonna get into the statistics as far as when you have two people and the doctor says, "Hey, you have a one in four chance "of your child having cystic fibrosis." We'll learn why it is he can make that prediction because we understand reproduction so well as far as what governs the combination of genes and cells and then the final part of this class is on evolution. Even ecology gets into evolution. So evolution is one of those central concepts of biology. You can't just pull this out and be like, well, I don't agree with some of the concepts. As we go through here, you'll see that once you understand what evolution is, there's really not a lot of controversy. But it requires you to have a proper understanding of it to be able to get to that point. The first characteristic is that all life is organized

9:26 and that's where we're gonna spend our first five or so lectures is looking at this complexity from the atoms and up, how cells are essentially organized. Now, we can go beyond cell. You'll see later on at the end of the semester that you can study biology at more complex levels of organization where we look at populations of the same species or we look at interactions between different species or we start incorporating environmental factors such as for the ecosystem and whatnot. Now, in your book, you're gonna have something like this, where it'll show you, in this kind of reverse S shape, from atoms all the way to the biosphere. It'll even give you some examples that I pull from as well for the quiz question.

10:19 Take notes on all of it because you don't know which one you're gonna get. Alright, so let's start with atoms. Now, we know from physics that obviously there are smaller particles and atoms but in biology, we don't have the energies that you typically get with something like the Large Hadron Collider in Switzerland, where they're slamming atoms together, splitting them up into smaller particles like muons and towels and quarks and whatnot. So we don't deal with those smaller constituents of biology because you don't deal with energies in nature of such magnitude. So that's why atoms is the lowest level of complexities because in any biological system, we look at some of the interactions that atoms have with one another to both look at how they come together to form more complex structures, as well as what some of the fundamental atoms that make up a life form, let's go over those real quick.

11:20 Though there are over 100 elements, actually 92 which are naturally occurring and others which we have created, so to speak in the laboratory. Of those 92 naturally occurring elements, there are only six that you will find in every living organism and I like to put it in this little pneumonic word called chnops, sounds like a alcoholic beverage. It's easy to remember but chnops which is carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur, okay? These six elements or what we call atoms will be found in every living organism. Now that doesn't mean that that's all we're made up of. In fact, humans have more calcium in our system than we do phosphorus and sulfur but not every living organism has calcium in it. We have a lot of calcium in our bone structure and that's required for our nervous system and our muscular system but it's not one of those elements that you would find in every living organism but you will find all six of these atoms

12:26 in living organisms in a wide variety of different shapes, from fats to nitrates and H2O, water. One of the most largest molecules or abundance of molecules in any living organism is water. So, atoms again, form the foundation and one of the first lectures we're gonna do for lecture three, which will be next week is to look at the big question, why do atoms interact with one another? Because when atoms start interacting with one another, they form the next level of complexity, which is molecules like water or ammonia or fats or proteins.

13:12 Some of these more large organic molecules that form the foundation for every living organisms and you know about carbohydrates, you know about fats and things of that sort. Those are organic molecules that have at their foundation, these elements, these atoms and that's why all living things are made of those is because the basic groups that are necessary for our biological organization are made up of those atoms. So a molecule is essentially a combination of different atoms forming a larger structure. You can have something as simple as a water molecule which is just H2O to something that is millions

13:58 upon millions of subunits which actually forms the foundation for who we are, like your DNA. I mean, there are some organic molecules that are just gargantuan in terms of their overall structure, okay? All right, so molecules can be put together in a wide variety of increasing complexities and this is what we call organelles. Now, organelles, what does that kind of remind you of? When you think of it, what's the first part of it? An organ, okay? So let's jump ahead real quick. Just name some organs of the body. Your heart, what does your heart do?

14:45 Circulates blood, pumps blood, okay. There was another organ. Liver, your skin, your brain, does any of the organs share the same function? Does your heart do the same thing as your brain? No, it doesn't do the same thing as your brain or your gonads, each one has essentially their own function. Well, organelles are to a cell as organs are to our body. Organelles are these small structures that have a specific role of function in the cell. Let me give you some examples. Now organelles are essentially combinations of different organic molecules and this is what we're gonna be studying. Is after we study how atoms come together and after we study how water behaves as a molecule and after we study the organic molecules like carbohydrates and proteins and fats, they will look out proteins and fats and carbohydrates come together to form these larger organelles. One of the more important organelles especially for our body are things like mitochondria.

15:54 Does anybody know what mitochondria does? Ever played the game Mitochondrial Eve? No? Alright, mitochondria are these kind of almost bean-shaped organelle that is found within your cells and they're the powerhouses of the cell. They pump out energy for the cell. So their main job is to take the foods which you eat and your cells absorb, the fats, the proteins, the carbohydrates and whatnot and turn them into usable energy. That's just one of many, many, many different organelles. Another organelle is what we call ribosome.

16:39 Ribosome is this large structure that essentially makes proteins, okay? So your body functions depending upon which proteins are made, like insulin. That's where diabetes comes into place. People who can't produce insulin properly or the cells are dead that normally produce insulin. That these ribosomes are organelles that actually manufacture the proteins, human growth hormone, insulin, your antibodies in your body, your hemoglobin for your blood, that those are proteins that get manufactured by these organelles. So we're gonna spend a considerable amount of time later on in that chapter on cells talking about the different types of organelles and their various functions but it's like organs. The heart has one job, it pumps blood,

17:27 regulates homeostasis or your blood pressure along with other organs in your body and they each have their job, the organelles the same way. The organelles are the structures in a cell each with their respective functions. Some of them digest food and make energy like the mitochondria, others protect your DNA, like the nucleus and whatnot. So there's a wide variety of organelles in the cell. Now, when you put all the organelles together and collectively integrate them with one another, that's when you get a cell and as we mentioned, this is the most basic unit of life. So a cell is made up of tens of organelles, I say tens, it's thousands of organelles but there's a little over 10 different types of organelles in any given cell. Some cells are very, very simple, like bacteria that don't necessarily have a lot of organelles. Other cells, like you and me, our cells have a wide variety of different organelles. So not all cells have the same composition of organelles.

18:40 For example, there's an organelle in plants called chloroplasts, that is responsible for the leaves of a plant to be able to undergo photosynthesis, which is capturing sunlight and turning it into things like sugars and fats. We can't do that because we don't have that organelle. So every organism has cells but those cells can behave differently based upon which organelles make them up, all right? There is some fundamental structure that is universal for all cells but there are fundamental differences as well based upon which organelles they have. So again, the level of complexity of a cell is just the grouping of different organelles together to form that self-sustaining unit that can reproduce itself, even if you take it from the larger organism like us. This is where stem cell therapy, and other things come into play and research. Now, sometimes this is where it ends. For example, a bacteria or another type of simple cell

19:42 called an archaea, they're unicellular organisms. So though they're not very complex, they're still a living organism but they're unicellular, which means that's the end of their level of complexity. They're just a cell, they don't have anything more, but in other organisms like us and plants and fungus and other types of species, we're what we call multicellular. So we actually have a higher level of complexity than they do, so how does that work? Well, the next level of complexity is what we call tissues. Tissues are just different combinations of cells. For example, in the human body are four different types of tissues. You've got muscle, you've got epithelial, you've got connective tissue and you've got nervous tissue. Now, you don't have to memorize those four but I'm just saying in the human body alone, we have four main types of tissues. Well, we have over 256 different types of cells and the different combinations of those cells

20:44 is what forms the different types of tissues. Some cells, when they come together will form muscle. Other cells when they come together form nervous tissue, and so on and so forth. Your brain, it's primarily made of nervous tissue but there's other tissues involved as well and that's where we get into organs. Organs are just different combinations of tissues. For example, your heart is pretty much made up of every type of tissue. You've got epithelial muscle, like cardiac muscle, you've got connective tissue and you've got neural tissue and so when those tissues come together to form a more complex structure, that's what we call an organ. Before you think that animals are the only organisms that have organs, let's talk about plants a little bit. For example, plants also have tissues and organs

21:36 and a lot of times people kind of skip over and think, how can plants have organs? Well, let me give you an example. Whenever you eat a piece of fruit off of a tree, you're eating its gonads, okay? Its ovaries, essentially. So think about the next time you have an apple, you're eating its ovaries, why? Because that houses the seeds and that's its reproductive organ essentially. Leaves are an organ. So anytime you see a leaf fall, the tree is shedding its organs essentially. So leaves are very complex structures made up of different plant tissues and each plant has their respective tissues and whatnot and when those come together to form a larger structure, then you get organs. So the roots of a tree are its organs. The leaves of the tree are its organs. The fruit is its reproductive organs. So even plants have organs, it's not just animals that have organs

22:39 and then when you put all of the organs together, you start forming what we call organ systems. For example, in the human body, we have what was called the cardiovascular system that makes up the heart, which is an organ and your blood vessels, which are organs as well and then you have that organ system. You have your brain which is an organ, your spinal column, which is an organ. You have an organ system, your nervous system. You've got your kidneys and your liver and your pancreas and your stomach and you've got all these organs of your digestive system. So in the human body alone, we have like 11 organ systems not every organism has that many. But trees, if you combine the roots with its vascular structure, with its leaves, that's an organ system. The roots bring up nutrients, they bring it up through its vascular system, it doesn't have a cardiovascular system, trees are heartless, suckers. But they do have the ability to push fluids through their cells into the leaves

23:39 and that's their organ system. Now, here's where things might get a little confusing. It's the only confusing part of all of this. Organism, on occasion, the book and other things will call a bacteria which is a single cell, an organism. So in this sense, organism refers to the higher level of complexity that's you and I and animals and plants and fungi or whatnot but on occasion, they call bacteria or a single-celled organism, okay? So just be aware of that, that when you're being tested on this at this point, it's gonna be this level of complexity, but this word is also used to describe a living cell like a bacteria as an organism, okay? So when I describe organism, it will be at this level, will be like when you have multiple organ systems working together to form a whole living unit, that would be an organism, okay?

24:46 Now, the last three are fairly easy. They're pretty much just definitions. So let's go through them. Population is essentially a collective group in a particular area of the same species. Basically, if you have a population of trees of the same species, they're all the same organism. The same group of species, that's what we call population. So you have human populations, we're all the same species, we're grouped into different cities and whatnot, so we have different populations. For plants, for animals, for fungi, for even bacteria, because they have a population of bacteria, you get strep throat, you got a population of bacteria in your throat. So, population is pretty much a grouping of the same species or same organism in a particular area.

25:41 Community looks at the interaction between all species in an area. So it doesn't just look at one type of organism. It looks at all the interactions between all organisms in that area. That's what we call a community. That's a very complex level of science but there are scientists who study community interaction and then finally, ecosystem. An ecosystem isn't just all of the living interactions but also all of the non-living interactions such as rainfall, temperature, nutrient flow and cycling. So it involves everything within an area, okay? But that is still restricted to a particular area. You have terrestrial ecosystems that are land based, you have aquatic ecosystems, which are based upon a particular area in the oceans or lakes or whatnot. And then the final pinnacle of biological interaction and study is our planet Earth, which we call biosphere. And that's basically the interactions between all ecosystems and that's a very, very complex science.

26:54 Don't take your data from the politician, take it from the scientists themselves and we'll talk more about that later on. In fact, as I mentioned, these last three concepts, those are the last three lectures that we're gonna go over this semester. Where we look at how biologists study populations 'cause this gets into extinction of species and collapses of ecosystem and those are of importance today. You hear that all the time, as far as climate change and whatnot. Collapsing of ecosystems and the ramifications of disappearance of species will have on the rest of the planet. So it's important that we understand at least the fundamentals so that you can make some informed decisions about policy and other things in the real world. Alright, so those are the definitions. If you want a slightly different definition, go to your book, it gives the same concept that I just gave but maybe a different example. And so the book's really good

27:56 about this kind of defining these concepts. Giving you some other examples beyond what I've given you here in class. Now, we might have to increase the level once we start having contact with other planets or aliens and whatnot but for now, we are an isolated biosphere, that's the highest level of complexity. All right, the second one is energy use and this is what somebody mentioned earlier. We know what a living thing is 'cause they usually have to get energy somehow. Now, most of what you and I are familiar with is the requirement to get energy by eating something else but not all living things have to consume other organisms to get their food. Some eat the feces off of the ground and that's their prerogative. Others can get their energy straight from the sun

28:49 and that's where plants and other organisms like protist come into play. Now, whether it is the consumption of another organism to get energy or the production of your own energy molecules as plants typically do, there's one universal word that describes all of that and that is metabolism. So let's define what metabolism is. Metabolism is just all of the chemical reactions that occur inside your cells. So metabolism is pretty much the swear word of biology majors, which is organic chemistry, it's chemistry inside cells and that is not an easy subject to study. But that's what metabolism is. When you eat fats and sugars and proteins and whatnot and your body breaks them down, that's our form of metabolism. Plants on the other hand, get energy straight from sunlight or from artificial light that we may put inside of a building but light is their energy source and then they take the chemicals from the air like carbon dioxide and water from the soil

29:57 and they can convert those into their own food molecules. They can turn those into sugars. In fact, that's how you and I get those energy molecules as they were first created by combining molecules together to form the carbohydrates and the fats and the proteins. This process which plants do is called photosynthesis. Photo means light, synthesis is the combination of these chemicals with the light energy to make the organic molecules that you and I need to be able to survive because we don't have the capacity to convert light into chemical energy. We have to wait to for these organisms and this is where we get our dependence also upon the stability of ecosystems. Our crops and the plants that provide the food for us and these other organisms, even algae, in their respective systems provide the energy for all living things. That's why we need to be concerned about the stability of our ecosystems on this planet.

30:58 Now, one of the laws that you're going to learn later on in more depth when we get into lecture seven is called the law of entropy. Now, this is a universal law of physics that scientists have seen throughout the universe in that energy is constantly lost as it travels through the atoms and the molecules that make up you and I. So we eat something, we incorporate that energy into our body but we're constantly losing it, usually in the form of things like heat. But because of that, that's why you have to eat every day. If you're able to recycle all of the energy and not lose any energy, you wouldn't have to hardly get it at all, okay? So we need to replenish that energy on a daily basis, for me on an hourly basis. Ultimately, by doing a number of things,

31:56 it depends upon how your living organism is structured and how you're gonna be able to do that because we need it to rebuild new structures. We're constantly repairing old ones. You get an abrasion on your skin, your red blood cells are dying every second and so you're making millions a minute. In fact, a third of the cells of your body that are renewed is your blood essentially, because of how important that is and we use a considerable amount of energy to reproduce. I'm not just talking about sex. I'm talking about producing the sex cells for that or the cells regenerating in your body, okay? So it's not always about sex but most of the time it is. So reproduction when we talk about this a little bit later, that's how this occurs is because of the energy that we get from the food which we're eating. Now, when we consume other organic matter, we call this cellular respiration. Now, when you think of the word respiration,

32:53 what do you think of? - [Student] Breathing. - [Instructor] Breathing and what do we breathe in? Oxygen, so oxygen is a key part of our metabolism. Not all organisms use oxygen. Some can actually use things like nitrogen. In fact, most of the air which you're breathing is nitrogen gas but you can't use that. But some organisms can use nitrogen in this process of cellular respiration. But the reason why we use oxygen is by far the most efficient way of consuming and breaking down fats and sugars and proteins. That's why our cells do it because it's the most advantageous and efficient way of actually getting energy and we call that cellular respiration. Now, when we look at ecosystems, you can actually categorize

33:43 all life into three different groups and this is one of your questions that you'll have is understanding the difference between these three groups. Again, this first lecture is more of an overview of what we're going to study this semester. So you're gonna see us talking about topics that we'll delve into deeper later on. This is one that we're not going to get to until, the end of the semester really but it's important that you understand some of the groupings of how living things use energy. So first and most important in any ecosystem, are what we call the producers. We also call them autotrophs. Auto, you mean self, these are organisms that have the ability to make their own food. That's why we call them producers. These are plants, these are other organisms called protist like algae, seaweed if you are from San Diego.

34:36 So I'm most familiar with brown algae or kelp but those aren't plants, they're actually what we call protist. They undergo photosynthesis, just like plants do. There's even some micro organisms like bacteria that can also undergo photosynthesis. These all belong to a category which we call producers or autotrophs because they have the ability from the sunlight to essentially make them their own food and then use it and process it. We on the other hand, animals are pretty much the main consumers of this planet. So the animal kingdom, we call ourselves heterotrophs. Hetero meaning we have to consume a different organism to essentially get our own food. So we cannot do what these organisms do, which is why we depend upon them because without them, the food runs out essentially. Without them producing these organic molecules for us to be able to survive, we will die off as a species. And then the last group aren't considered consumers

35:38 because they don't actually eat another organism. They essentially break down waste products. A tree drops its leaves in the winter and you get what we call decomposition. They're not actually eating the tree, tree is not dead but they are recycling the nutrients and the leftover energy that's found in that organic matter, okay? So they're not eating the leaves straight off of the tree, which is why they're not a consumer but they are breaking it down once it's dead or falling off. Same thing is true from feces, fungi, bacteria and whatnot will consume much of the energy that's left over from defecation. Animals can only actually extract about 10% of the energy of the food which we eat, that's why we eat so much and that's why we defecate so much, is because most of it just goes right through us, whether it's fiber or whether it's other structures that we just cannot metabolize or break down.

36:40 All right, so those are the three groups and one of the questions would essentially describe like I just did one of those three groups and you've gotta tell me, if that's a producer or that's a consumer or that's a decomposer. Let me show you a picture of what's in your book that illustrates these three groups. As I mentioned, entropy is a law that we're gonna get to later on is the process of energy loss, okay? As energy is transferred from one organism to the next, there's always going to be energy loss to the environment that's not used biologically. So producers first get the energy from the sun and that's really where our dependence upon the sun is, is without sunlight, there is no life on this planet. So the sun fuels the metabolism of the plants and they make their own food molecules. Then we eat the plant or eat something that eat the plant or eat something that ate the something that ate the plant

37:36 or rather do the latter and then whatever is left over, gets whatever energy through the organic molecules leftover gets finished off by much of those decomposers. Alright, so that is how living things use energy. So look for key words like metabolism and whatnot or photosynthesis and cellular respiration. These are typically found in the test questions where I'm describing this process and these next set of questions pretty much have this format. Now, I'm not gonna do any of the clicker questions for this yet but they have this format, where they have the five characteristics that we're going over now, I will describe one of them

38:22 and you've gotta tell me which one I'm describing. It's that simple, okay? So, I'll get to those later after we've covered most of these. All right but that's energy. Now this is probably the most difficult concept of the five. The one that people haven't heard as much of, we all understand it but you may not have heard the word homeostasis. So let's talk about homeostasis. All life must maintain what we call homeostasis but the problem is homeostasis is not the same thing for all living organisms, okay? Some organisms can live in hydrothermal vents, areas that are so hot that you and I would not be able to survive in

39:08 but that's homeostasis for them. We live in various environments that are good for us. Others can live in other environments. So really what homeostasis is, is the organism maintaining internal equilibrium, okay? So let me give some examples of what we mean by internal equilibrium. Let's talk about people 'cause it's the easiest thing, like I said, amongst the many things that our body regulates, one of them is temperature. We like to have about a temperature of 98.6. That's where the cells function best in our body, okay? Other organisms might function at different temperatures but that's homeostasis for us. So two things can happen to disrupt our homeostasis. In fact, that's the definition of disease

39:59 is the disruption of homeostasis and that's what we would call disease. Now you go outside and it's butt cold out there. So when you go outside, what does your body do? Because all of a sudden now you're losing tons of heat, what is your body gonna do to try to maintain homeostasis? It shivers, now the big question is why? Why is that an automatic response that our nervous system gives to us? Well, let's go back one slide. When our muscles shiver, the muscles are actually doing these mini contractions. In order to do the mini contractions, they're consuming energy and in the energy consumption process, heat is a byproduct. That's the same reason why when you're exercising your body heats up because in the consumption of energy, due to law of entropy, heat is a byproduct as a result of that, it's wasted energy, so to speak, as it's given up. So that's what your body's doing when you shiver.

40:58 You are heating your body up. It is generating energy through entropy or causing heat to be generated and that's why your body is doing that, is trying to maintain homeostasis by warming yourself back up. Now the opposite is true. You go outside and it's hot or you could be inside and it's really, really hot, what does your body do to cool down? - [Students] Sweat. - [Instructor] We sweat. All right, so what happens when we sweat? Well, when we sweat, the water in our cells, in our body takes that heat, that excess energy and that's why you sweat when you exercise as well, you might try to avoid it but when you exercise, the excess heat and energy is not good. Your body does not function well at 100 degrees Fahrenheit or 101, I just got over that stupid plague, where our fever was 103 or 104, explain why in a second why we regenerate fevers during the viral infection or whatever the case may be but our body doesn't like that and so when we get too hot,

42:04 the water in our body absorbs that heat. When it gets to our skin, the only way that we can remove the heat is to have the water evaporate and when the water goes from a liquid to a gas state, it requires a tremendous amount of energy. Well, that energy that is consumed and the evaporation process cools us down, essentially draws the heat away from our skin in our body, and it cools our body down. So whether we shiver or whether we sweat, those are two ways in which we try to maintain homeostasis in our internal body temperature and you could do the same thing for blood pressure and calcium levels in your body. And whatever the case may be, there are so many things that our organism does to maintain homeostasis, I can't even name 1,000 of them. But for testing purposes, you'll typically get one of these scenarios that I just went over, that our body either sweats or it shivers, essentially to heat us up or to cool us down.

43:08 Now, just to give you an idea, this isn't on the quiz but just to give an idea, the reason why we get a fever when we get an infection is because when the body temperature goes up just a little bit, the metabolism in our body speeds up and that metabolism is what's necessary for the immune system to fight off the infection. So a slight temperature is good because it essentially increases and speeds up our metabolism but in some scenarios when your temperature gets up to 104, 105, this is the danger zone because at that temperature, your cells start to die and that's where you can get brain damage and other things like that. Your cells do not work at 105 or 106 degrees Fahrenheit. Things start messing up and we'll go into more detail later about how it messes up but that is not a good temperature for us.

44:05 And then the reason why our body allows that to happen without us sweating and that's why when you break a sweat, your body is restoring homeostasis is there's a little internal mechanism in our brain that resets our internal thermostat to allow our temperature to go higher without sweating, so anyway. All right now, reproduction. Again, it's not all about sex. In fact, most of reproduction on our planet is what we call asexual reproduction or mitosis. Mitosis is the actual physical process of the cell splitting but the overall process of cellular reproduction as we call it, is called asexual reproduction. Now, you and I undergo mitosis but we don't undergo asexual reproduction. So what's the difference? Well, mitosis or cell division, that's going on all the time in your body.

45:07 You use mitosis primarily for cell renewal and regeneration. You get a cut, you need to repair the skin, that's mitosis. Your red blood cells wear out, which they do every four months after they're created, you make new ones, you're constantly making new cells. In fact, after about 10 years, you don't have hardly any of the same cells that you had 10 years ago. You've regenerated pretty much every cell in your body but a few. So you are a different person every decade, so to speak physically because you're constantly regenerating yourselves. Now, for some organisms like bacteria, which are single-celled organisms, their mitosis, so to speak, is their only mode of reproduction and it's really just a cloning process. And that's why we call it asexual reproduction is because it doesn't require the combination of genetics between two different species. They pretty much just copy themselves. Now, you don't have to be a single-celled organism to do that. In fact, a lot of plants clone themselves.

46:12 You can take a little bit of a plant tissue, put it in the right environment like potato, this is how potato farming works, put it in the right environment and it'll grow into a whole new plant. So some species even more complex species can clone themselves as well as plant as fungi, there's even a couple animals that can do that. We call it the Hydra, Greek mythology. cut the head off, kill Hydra, I like this stuff from Avengers. Anyway, Captain America, anyway. Animals like the Hydra, they can clone themselves, but most animals can't. Most animals undergo a different process which we call meiosis or sexual reproduction. So what's the fundamental difference between those two?

46:57 Mitosis is a cloning process. Your cells in your body regenerate themselves, that's mitosis or an organism copies itself, that's mitosis. But meiosis is where you take the genetics from usually two different species. Sometimes an organism can have sex with itself, so to speak, and as for plants do both and there's even some animals that can have sex with themselves and produce their own offspring but ultimately, sexual reproduction is just genetic recombination. You're not cloning the organism, you are mix and matching the genetics, you're literally scrambling the genetics up. Now, between these two modes of reproduction, sexual reproduction has the greatest evolutionary advantage and the reason for that is because species that reproduce sexually have the greatest amount of genetic variation.

47:55 When we talk about evolution here in just a second, you'll see that variation is key to survival. The less variety there is in a species, the less ability they have to adapt to changing conditions in their environment and usually die off, In fact 99% of the species that have lived on this planet have died off, even though a good number of them have been sexually reproducing. So even sexually reproducing species can go extinct but they have a greater advantage over species that purely clone themselves because this variation provides the diversity necessary in the species as a whole to survive. Alright, so we undergo both mitosis and meiosis but we do not clone ourselves. Why would you want to? The world can only handle one of me and so ultimately, there's no reason to clone ourselves as a species but most of the species on the planet clone themselves through asexual reproduction, through mitosis. We use mitosis primarily for growth and regeneration.

49:01 Meiosis on the other hand, gives the species genetic diversity, a greater amount of genetic diversity because sperm and egg come together, unite, create a unique offspring, okay? Now, plants they do both, they can clone themselves and their pollen which is their sperm, you have that next time you sneeze, you got sperm in your nose and the pollen reaches essentially the flowers and cross pollinate and whatnot creating the ovary, which is the fruit that you're eating, and creates the seeds from that for the next generation. So I'm gonna ruin a lot of things for you in this semester. Okay, last but definitely not least, evolution.

49:52 All life evolves, okay? You could say that the fundamentals of evolution is genetics is because all cells have DNA and then the DNA is what gets passed on from one generation to the next through reproduction and that's what ultimately gets changed and allows for the species to have variation to adapt. So we're gonna delve very deep into evolution later on but this is just kind of give you an overview. When you look at a species in its environment, you will see that the reason why the species has the phenotypes, as we call it or traits, is due to the fact that that is the most advantageous for that environment and that has over time adapted and caused that to be the prominent trait because of its advantage. Let me give you some examples. Camouflage is one of the huge things that happens especially in predator prey relationships. Where you have this adder snake and look how perfectly camouflaged it is in its environment.

51:03 Any variation from this camouflage, if all of a sudden you start getting some adder snakes that are a little more green won't really be advantageous because the prey can easily avoid them, but due to their ability to hide in their environment. Now prey has the same thing, you've ever seen insects that look like leaves or sticks or whatnot, that's evolution as well. Their ability to survive based upon the adaptations to their particular environment and you see it across all life. So we look at the genetic diversity within any species and you'll find that each has a strategy that has evolved and adapted to their environment. It doesn't mean that that's the best thing. For example, if you take the adder snake and transplant it to another environment, it'll probably die off because it's not adapted to that particular environment and that's what happens a lot of times when the environment changes and the species can't adapt, is they go extinct.

52:00 And that's what we're looking at today with a lot of the climate change and things of that sort is it's the environments are changing so rapidly that the species don't have the time to adapt. It's too drastic changes and they don't survive and that causes ecosystems to collapse and other problems.