 The first characteristic that all living things exhibit is this concept of hierarchical organization. And this is fundamental to understanding how life functions and why it works the way it does because it's got these levels of organization that at each level, in fact, at each level there are emergent properties that are characteristics of just that level. Okay. So let's write this down. Hierarchical, hierarchical organization. And in fact, there are some very, very small levels of organization, small into the like physics, like crazy quantum physics level of tininess of matter. We're not going there. And all the way up to the biome, which is our entire planet and its atmosphere and all the critters and everything that are on it. Let's start with the subatomic particles that we're going to look at in this class. So I'm going to make you a list. And I'm going to start from the smallest and we're going to move to big. And so the smallest level of organization that we're going to look at is a subatomic particle. Subatomic particle. And tell me, what is an example of a subatomic particle? We've got protons, neutrons, and electrons. And if you've never heard of this, we've got an entire lecture coming up day after the next one on chemistry, which is we'll be talking about these different subatomic particles and what they do and why they're significant. If we take subatomic particles, like protons, neutrons, and electrons, and put them together, so let's take groups of subatomic particles and we're going to make what? Sub below the atom. We're going to make atoms. Atoms are the basic building block of all matter. And again, we're going to spend an entire lecture. Yeah, you might wish. You might be glad that we're only spending a lecture. We will understand shortly that all function, all critter function really can be boiled down to what's happening at the atomic level of organization, where atoms and molecules are interacting with each other and causing you to exist, which is phenomenal. When you take atoms and you put them together to build something bigger, something a little more complicated, you get molecules. And molecules are just, it's like Legos. We're going to take molecules and we're going to, we're going to take atoms and we're going to put them together like Legos and now we've got a molecule. Now I'm going to do, so that I can try and fit my entire thing on one page. I'm going to go this direction now. I feel like I'm playing dominoes. When I play dominoes with my kids, they, their domino trains like go all over the place. We had the airplane domino going on with one of my, whatever. So that's what I'm doing. I'm making a crazy domino train right now. Because if we take molecules and put them together into basically bigger molecules, but a level of organization that has new characteristics, we get biomolecules. And I need to tell you what those biomolecules are. We have four categories of biomolecules. So molecules are groups of atoms. And now we're going to put our groups of atoms, our molecules together to get these specialized molecules that are big and they're found in living systems and we have four categories. We have nucleic acids, nucleic acids. That's like DNA. That's your genetic material. We have proteins. Proteins are made of amino acids. That builds, rah, rah, rah, like that giant massive biceps. Domest with me because it's really strong. Lipids. Lipids are basically fats and carbohydrates. That's our other group of biomolecules. So these are all big examples, big molecules that are used to build living things. If we combine, this is a tricky place. People often get mixed up here. If we, we can use biomolecules to build structures. They're like little tiny machines. And once you see how these things work, you're going to be like, what? We have those things inside our bodies, inside our cells, inside our what, 100 trillion cells. Okay, 10 trillion cells. Yes, you do. They're called organelles. Organelles. And organelles are little, they're machines. They're machines that are found inside what? Cells. Now, let's just take a minute to do something amazing like this. We've got the cellular level of organization because we've got these little machines, these little organelles, and we put them together and now we have the first level of organization where life is evident. Before this, you didn't have, none of this stuff is alive. The organelles aren't alive. They're machines. They do work, but they're not alive. Only the cell is the first level where we see characteristics of life, one of which is this hierarchical organization. Okay, now you have cells. Now you have living things. Well, we can combine these living things. We can combine these cells together. And if you get a group of cells working together for a common function, we get tissues. The study of tissues is histology. We will use the microscopes to study or to look at some tissues in this class. If you're moving forward to human anatomy next, you will spend a good chunk of time studying tissues in that class. But it's a group of cells that are working together for a common function. You can take tissues and you can use them, like Kleenex tissues, like adipose tissues, and epithelial tissues, and connective tissues, and muscle tissues, and nervous tissue. And we can put them together to build organs. So an organ is a group of different kind of tissues that are all working together for a common function. Heart, a brain, a bone. Your humerus is actually an organ. Bones are groups of lots of different kinds of tissues that are working together to carry out a common function. Muscles, my gigantic biceps brachii that I'm so proud to show you here, is an example of an organ. There's a whole bunch of different tissue types in there that are working together. Organs, if they work together for a common function, are you seeing a little pattern here? Then you get organ systems. And an organ system, an example, a cardiovascular system, the respiratory system, the digestive system. Here we've got multiple different organs that are working together, and they're all working together to do the same basic function. And organ systems, when you have a whole group of them working together to carry out, to maintain homeostasis, which we'll talk about in a second, organ systems make up an organism. Now, where does an organism start and where does it end? That's actually another rather philosophical conversation that we could have. We'll try to avoid, we've been doing way too much philosophy. It like hurts my brain. But we're not done. We actually get to keep going. And we're going to keep going into the world. Maybe we'll take it and make it green. Because groups of organisms can live together and work together like all the same kinds of critters can live together like a little family or a little city. And that's called a population. So groups of, so a population is one species of critter, all living together and working together. And I mean, think about this. Do we live in isolated populations? My house is not an isolated population because there are other human organisms, my husband, my two children. But we also have other critters, other species living with us. And I don't even want to think. I'll just tell you the ones that are living with us that are, that I would actually admit. I don't even want to think about the ones that are living in the dust bunny piles under my dresser. That's a little frightening. We have a chicken named Mabel Madeline. She likes to come in the house whenever she can squeeze in through a door that a boy leaves open. Oh, that happens all the time. We have a dog named Lottie Dog. We have a cat named Lois. These are all different species. So we actually live in a community, a group of multiple species, many species living together. And our community can actually, we can make the whole community if we look at all these different species and their non-living environment. Then we have a ecosystem. So an ecosystem is a whole bunch of communities plus the non-living environment. And then the whole thing, I have to make it in a whole new color. The whole thing, all of it makes up the biosphere. Whoa, did you follow my little path? Look, I'm going to make it yellow because yellow is my favorite color. You don't know that yet, but it is. And yellow is a hard color to use because you got to get it just right or else you can't see it. We started with subatomic particles. This was the simplest, the smallest. We made it all the way to the biosphere. How did we do it? We went through atoms, then molecules, then biomolecules, then organelles, then cells, first living system. Then tissues, then organs and organ systems and organisms to populations, communities, ecosystems, and to the biosphere. Looks like the yellow brick road. And all living things display this kind of hierarchical organization. Just because something is hierarchically organized doesn't mean that it is necessary a lot, necessarily alive. So there are other characteristics. In fact, there are four more characteristics that we're going to look at. And the next one is homeostasis. So let's find out what that is.