Bare Bones Biology Transcript 011 – Life?

The redbird sings over his mate who is nesting in a tree by my driveway. It’s life. We’re talking about biology, the study of life. But what is life? What is it really?

Well, to make a long story short, one definition of life is the ability to reproduce one’s kind and to respond to the environment. That’s a good definition, because rocks, for example, do not reproduce in kind. And if they get too hot or too cold. They just sit there. Putting on a coat when we are cold, making antibodies if we run across a disease. All these things are responses to our environment.

The most basic unit of life on earth, the smallest unit that can do these things for itself, is the cell. Cells can respond to their environment, very much as we can, and they can reproduce their own kind. Cells are alive, we are alive, because we are made of cells.

Living cells are made of organic molecules. The molecules are not alive. They can not reproduce themselves outside of a cell. And living cells are also made of water and some other things. We are made of billions of cells, therefore we also are made of organic molecules and water and a few other things. The organic molecules, such as genes, proteins, carbohydrates and lipids are absolutely necessary to life, and they are made by living cells, but as I said they are not of themselves alive. The cell is the most basic unit of life. Still, it’s the genes inside the cell that make that cell capable of being alive. Not only the genes, the genes and all the other organic molecules working together.

But primarily the genes regulate the functions of being alive. So. How do they do this? One way they do this is to regulate the proteins inside your cells. Another way is to regulate when and where each different kind of protein is made.

So if you need a protein in your brain (probably you have heard of serotonin, but there are a lot of proteins in your brain) then some specific gene is responsible for making each of the different proteins. And some other gene is responsible for turning the first gene on at the right time and place in your brain, and not in your big toe or someplace else it is not supposed to be. Or you can think of enzymes. These are proteins that cause chemical reactions to happen. Each enzyme regulates a specific function. Enzymes control nearly all the functions of cells, from, photosynthesis to cell division, and they also control the different behaviors of all the different species — how to make a spider web, how to make babies — all these processes are directed by multiple enzymes and the enzymes are regulated by the genes.

And genes even control ecosystems, by controlling the behaviors of organisms. It is the interacting behaviors of all the species on earth that make it possible for ecosystems to survive, and to respond to their environments, and to reproduce themselves. Ecosystems are the largest units of life on earth.

But, you say, surely humans are different. And yes indeed we are different.

While the spider weaves its web, over and over again the same, generation after generation. We, on the other hand, can learn from our language and our books and our mathematics, from people on the other side of the globe or from people who lived 2500 years ago, and we have been given the awesome responsibility to decide for ourselves how we choose to behave within the ecosystem that gives us life. We are all making decisions of this sort every day, usually without knowing it.

I think it’s better to know.

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