What is Life?
What is life? This is a question I will not be able to fully answer for you, although I'll attempt to define it later. Even among living creatures here on Earth, what life actually is, is still a matter of nuanced debate. For example, some people are still debating whether viruses are technically alive or not. If we can't settle the debate here on Earth, we may not be able to recognize very different life forms on other planets, even if they hit us in the face.
Other lessons will explore the possibility of life on other planets, but this lesson will focus on establishing some key basics about the nature of life right here on Earth that are not in question so we can later compare that to potential life in the far reaches of the universe.
The Definition of Life
If I were to attempt a definition of life, as evidenced by processes here on Earth and Earth alone, I would say it goes something like this: life is a process which involves the metabolism, growth, and reproduction of an organism and that organism's manipulation of and adaptation to its surroundings for its survival.
The basic nature of all life on Earth includes some key underlying features, such as carbon. We are carbon-based life. But carbon alone is not nearly enough to actually account for the definition of life I gave. A lump of carbon is as good as a lump of coal. There has to be more than that, obviously.
The Processes of Life
Remember, life is a process. For a process like metabolism to occur, there have to be actions that are carried out. For actions to be carried out, there have to be instructions for those actions.
It's like a manufacturing plant where something like a TV is made. The process of making a TV involves actions performed in an assembly line by a lot of different people and even robots. But those people and robots need instructions for their actions. People are told what to do with written or spoken words. Robots are told what to do via computer code.
Our body's computer code, which accounts for the processes in your body that help you grow and keep you alive, is based namely on DNA, deoxyribonucleic acid, although RNA, ribonucleic acid, plays an important role, as well. The instructions involved in life, DNA, must be passed down to offspring during reproduction. Sort of like a plant manager may copy her instructions to a colleague to pass along to someone else. When reproduction occurs, DNA is copied down for the next generation.
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