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A look at what makes up life

All life has seven characteristics in common: they have some sort of order, respond to changes in their environment, reproduce, grow and develop, regulate themselves, do things to maintain homeostasis, and process energy.

When plants notice that sunlight comes from a certain place, they bend themselves to be able to capture as much of it as they can. Therefore, we sometimes see them climbing fences. Organisms also need to be able to reproduce without any outside help. Viruses need a host to reproduce, which is one of the reasons  they aren’t considered to be living.

Homeostasis is an internal state of balance. For example, when it’s hot outside, our bodies maintain homeostasis by producing sweat and cooling us down. And when it’s cold outside, we shiver so that we can be warm, and thus, maintain homeostasis. Organisms process energy through the food they eat. Everything we eat becomes converted into energy we can use to move and think.

Life’s characteristic of order can be exhibited through the levels of organization. The biosphere is all life on Earth.

Zooming in, we get an ecosystem, which is all the organisms, including animals, plants and bacteria, that live there and the environment’s physical and chemical properties such as temperature, humidity and pH. If we look a little closer, we’ll see the communities that make up an ecosystem, which consist of only the organisms that make up a certain area.

Then, we have populations, which are specific species of organisms. For example, a pride of lions is a population. The specific organism in a population is the next level of organization.

Then, when we zoom into an organism, we can see that they are made up of many organ systems. For example, in humans, we have the circulatory system, the digestive system, the nervous system, etc. These  systems are made up of organs (e.g. lungs, heart, brain), which are made up of tissues. These tissues are made up of cells. Cells are the basic unit of life and are made up of macromolecules.

Phospholipids are a macromolecule that make up the outer layer of cells. These macromolecules are made up of molecules such as carbon molecules. These carbon molecules are made up of carbon atoms and so at the very last level of organization, we have atoms.

Life on Earth has occurred because Earth is a good distance away from the sun. Like Venus and Mars, Earth is neither too far nor too close, allowing water in its liquid form to exist. This region is called the habitable zone. Earth has a magnetic core, which is the shield that protects it from solar winds, which can blow away the atmosphere, and the cosmic rays, which are very harmful to life.

The atmosphere has greenhouse gases that allow Earth to stay warm enough to sustain life. But too many of these gases could make Earth too warm and kill the organisms. Water is a universal solvent, and it allows all the chemical reactions in our body to take place, which lets us live. And Earth has oxygen (which humans need to breathe but there are many organisms that will die because of it), which contributes to an atmosphere that allows Earth to stay warm. So other planets would need to be in the “Goldilocks” zone that Earth is in, have a magnetic core, have an atmosphere that allows the planet to be warm, and contain water and oxygen to be able to contain life.

But here’s an interesting perspective: life on Earth is the only form of life we know. Just because organisms on Earth specifically need water or need to be in the “Goldilocks” zone doesn’t mean that life on other planets need to as well. Our definition of life is constrained because it’s only based on what we know about Earth.

So other planets could contain life, just not in the traditional sense we think life is.

VAAGEESHA DAS is a senior at Morgantown High School. Information comes from: