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  • Hi. It's Mr. Andersen. Today I'm going to talk about the hierarchy of life.

  • Biology is organized from the very small to the very large which would be the biosphere.

  • And so each of these different levels is called a system. And a system is separated from its

  • surroundings using a boundary. And so an example, non-biological example, if we have a city

  • that would be a system. Inside that we have a school. Inside that we have a classroom.

  • And so it's kind of like these Russian dolls, with the larger ones enveloping the small

  • ones. And so as we move through these hierarchy of life, one term that I want you to keep

  • in the back of your head is emergent properties. In other words, with each level, as we get

  • to a level, there's going to be a property or properties that show up that weren't there

  • on the level before. And so let me give you an example. This right here is a soldier.

  • This would be a termite protecting the mound. But each of these termites inside are an individual

  • system of their own. They're working together in a system of a colony. And they're actually

  • farming a little fungus that grows within the termite mound. And if we even look at

  • a larger scale, this right here is a termite cathedral. Now a termite cathedral is so big

  • that it faces a major problem. Carbon dioxide is going to build up on the inside of these

  • as they're all doing cellular respiration. And so they could all asphyxiate if there

  • wasn't some way to remove that. And so they're designed so that as the wind blows, there's

  • ventilation. We can actually sweep that carbon dioxide away and new oxygen in its place.

  • Now you might think, wow, smart termite. How did they figure that out? Well basically think

  • of it as 80 different termite cathedrals that are a little bit smaller. And in some of those

  • all the termites die. Well their genes would die with them. And those that have any kind

  • of a ventilation are going to be able to survive. And so we get emergent property showing up.

  • So here it is. Your hierarchy of life from atom all the way to biosphere. And as you

  • get good at biology you'll just simply memorize these. Let's start with the first one, which

  • is not really biology at all, this is an atom. This is an important atom called carbon because

  • it has four valence electrons and so it's very good at bonding. If we go to the next

  • level, that would be the molecule. And so here's carbon again. But it's bonded to two

  • oxygen molecules. And so now it's carbon dioxide. What would be an emergent property? Well that

  • would be the idea that it's more stable. It's actually formed and it's sharing these electrons

  • and so it's now bonded. And so that would be something that we find in molecules. Go

  • to the next level, we have what are called macromolecules or large molecules. The four

  • different types remember are carbohydrates, proteins, lipids and nucleic acids. An emergent

  • property in them is that they're built up of monomers. So repeating blocks. And they

  • eventually show what's called polymerization. Next if we go, we get to the level of the

  • organelle. These are going to be the tiny organs inside cells. This right here would

  • be the plasma membrane. It's made up of macromolecules. It's made up of this phosphate group on the

  • top. And it gives it this emergent property. The ability to separate the outside and the

  • inside of a cell. Speaking of cells this would be a red blood cell. A red blood cell is going

  • to have that plasma membrane inside it, but it's also going to have the hemoglobin protein

  • that I just showed just a second ago. And so now it's emergent property is that it can

  • move around and it can actually grab oxygen and then move that to different parts in the

  • body. Next we go to the level of a tissue. A tissue is made up of a bunch of cells that

  • are working together. This is actually a muscle cell. You can see that there are some striations

  • in it. And we look down here we can see these intercalated disks and so we know that this

  • is cardiac muscle. And so it does a specific function, which is contract, to beat your

  • heart. But it also can receive nerve signals. And so that nervous signal can kind of wash

  • it across it. Okay. When you have a bunch of tissues that are organized and working

  • together we have what's called an organ. And this one is called the heart. Now this is

  • going to have all four different types of tissues inside it. It's going to have muscle

  • tissue, nervous tissue, connective tissue. It's going to have epithelial tissue on the

  • inside. And so all those tissues are working together with a single purpose. That heart

  • is sitting inside what's called an organ system. And so this would be the circulatory system.

  • Here we have our red blood cell. But we also have the heart and all of these arteries and

  • veins and they're working together to move that red blood cell around your body. Next

  • we have an organism. This is called an elk. An elk is made up of a number of organ systems

  • that are working together. Organisms are organized into a population. So this would be all of

  • the elk that are living in one area at a time. Once we get a number of different organisms

  • living in one area at one time, now we have all these intraspecies interactions between

  • you know bull elk and cow elk. And so basically this would be an emergent property we find

  • at the level of the population. Next we have all of these different populations interacting

  • together. And so this would be a community. It's all biotic at this point. So they're

  • all living things. But we're going to have, this looks like predation right here. This

  • would be predation. We're going to have, you know, competition. We're going to have parasitism.

  • And so we have all these interactions between different populations at the level of a community.

  • Next we go to the level of the ecosystem. I happen to live right here. Right on the

  • border of one of the greatest ecosystems in the world, the Greater Yellowstone Ecosystem.

  • What have we added when we get to the level of an ecosystem? Now we're adding abiotic

  • material. So we're adding water. We're adding chemistry. We're adding light. And all of

  • these things go together to form an ecosystem. Interesting, where do we put this boundary?

  • Well basically they discovered the Greater Yellowstone Ecosystem the way they figured

  • out the boundaries. They looked at wherever grizzly bears are found and we said this is

  • going to be that ecosystem. Now we go to the level of a biome. A biome is going to be ecosystems

  • that have similar climate. So they're going to have the same temperature and they're going

  • to have the same precipitation throughout the year. And so tropical rain forest or desert.

  • Or this would be a northwestern coniferous forest. Or the tundra. Or the taiga. And so

  • these are all types of biomes. And the biomes together form what's called the biosphere.

  • And the biosphere on our planet is wherever we find life. And that goes from deep in the

  • ocean to high in the atmosphere. And that is the hierarchy of life. So I hope that's

  • helpful.

Hi. It's Mr. Andersen. Today I'm going to talk about the hierarchy of life.

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B1 中級

生命的層次結構 (The Hierarchy of Life)

  • 53 11
    Cheng-Hong Liu 發佈於 2021 年 01 月 14 日
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