What a fascinating question! I study psychology, which I view as a specialized area in the study of biology. Therefore I will reply to your question from this particular perspective.

To start, I think you have correctly identified the dramatic impact that life, even the early prokaryotes, has had on the Earth. For example, around 2 billion years ago a prokaryote known as cyanobacterium was the first life-form to evolve the ability to transform sunlight and carbon-dioxide into energy for the cell. We call this process photosynthesis.

Photosynthesis, as a side effect, produces oxygen. Billions of years ago, oxygen was actually very rare on Earth and was a deadly toxin to most lifeforms. Cyanobacteria were very successful and pumped massive amounts of oxygen into the atmosphere – resulting in the mass extinction of many forms of life. So you’re right, prokaryotes fundamentally changed the chemical composition of the land and atmosphere of Earth, which in turn has shaped the evolution of life.

However we have to keep in mind that the process of evolution by natural selection has no foresight, that is, the prokaryotes did not intend to change the atmosphere for any later purpose; it was simply the result of a chemical reaction. So I would argue that the organisms that are most fit with their environment just happen, by chance, to best survive and reproduce. As a byproduct of this, the earth and other life can be dramatically changed. But this all happens without any goal, intentions, or desires; rather it happens by the laws of chemistry.

As a psychology student, I cannot help but also note that humans have a strong tendency to think that random events are actually the product of design or intention, what we term teleological thinking.

Thank you again for the interesting question,

Scientists don't know how prokaryotes developed from non-living chemicals. We have been studying the problem for almost 100 years, and we have many ideas. But we are still a long way from knowing about any way to produce life from non-living chemicals.

We do know, though, that life didn't start in order to Do Something, like re-utilizing ingredients for preservation. Chemical reactions just happened. It's the same, now, with evolution. There will be a change - a mutation, for example - and maybe something useful will come from it, or maybe it will just kill off the plant or animal that got the mutation. So all the amazing things we see in plants and animals just happened as the ancient plants and animals changed, very very very slowly! It was the same when life began - changes happened very very very slowly, and finally there were living things for the first time.

Scientists think prokaryotes first evolved on Earth 3.8 billion years ago! It’s likely that prokaryotes formed spontaneously in Earth’s early atmosphere.

There is no evidence that the Earth actively created prokaryotes to serve some purpose, be it preservation or otherwise. The evidence that we have suggests that prokaryotes merely formed as a result of a chemical reaction from what chemicals were around at the time. However, while there is no scientific reason to suggest that the earth is a supernatural entity or that such a purposeful creation could have happened, it is also impossible to completely disprove it. It does violate Ockham's Razor, though ("the simplest solution is most often the best").

So that’s an interesting idea, but there a couple important considerations. For one, science tries to connect cause and effect to attempt to understand how something works. Science does not directly address why something happens. So the scientific view that life emerged spontaneously on Earth doesn’t consider why this happens, it only tries to understand how it could’ve happened. So by this viewpoint, the emergence of prokaryotes could have been a random event without a specific driving force. The planet Earth is not alive and only follows the laws of physics, so it could not have directed the development of life for a purpose. Therefore, the Earth itself can not care about its preservation because that would imply a life-like aspect. Also, very few chemical substances can freely leave the earth; the only substances light enough to leave the atmosphere are hydrogen and helium gases. It is true that leaving things such as prokaryotes tend to collect ingredients by storing large amounts of complex molecules in the small volume of the cell. However, it’s not clear that this benefits any entity, but the living things themselves.

That’s an interesting question. You’re right that prokaryotes like bacteria are important in how different molecules move through the biosphere. Some bacteria take nitrogen out of the atmosphere and turn it into a form that plants can use. Some break down complex molecules for energy. Some protect us from diseases. Once you know all that bacteria do, it’s almost impossible to imagine a world without them.

There’s nothing wrong with looking at the world in different ways. Many religions and philosophies teach that things happen for a reason. People using this way of looking at the world may believe that things in the past or present happen so that something can happen in the future.

A person might use more than one way to look at the world. Many people use science to figure out some things, like how to cure a disease, why animals behave a certain way, or how to make a battery less toxic. The same people may use non-science ways of thinking about things like how we should treat other people, animals, or the world.

There are some things that Earth has in common with living things and some ways that it is different. Can you think of some?

You may be interested in studying ecosystem ecology.