Wikijunior:Biology/Origin of Life

Origin of Life
About a billion years after the formation of the earth, there were protozoa and stromatolite. It is not known how life evolved. There are various theories, one of which is presented below. Living things control their internal chemistry. A main problem in the transition from chemistry to biology is self-regulation. A comparison with the market economy should clarify this.

- When the warehouses in a factory are full, production is stopped. (End products inhibit chemical reactions.) In a market economy, production is regulated by supply and demand. (In chemistry, starting products and end products control the reaction.)

- There is a problem with waste products in the industry. These must be disposed of. This reduces the profit. Many entrepreneurs have become rich because they came up with an idea of how to make something valuable out of the waste products. The waste product became the raw material. (The end product of one chemical reaction can become the starting product of another reaction.)

* Step 1: Cycle Starting products and catalysts promote chemical reactions. After the reaction, the catalysts are released and are available for further reactions. That's why it's called a cycle. End products inhibit chemical reactions.

* Step 2: Hypercycle The end product of a chemical reaction becomes the starting product in another reaction. This restarts the production of this substance.

Both cycles control and sustain each other in a symbiosis.

The metabolic processes of every cell are based on a large number of hypercycles. According to the symbiosis-based definition, hypercycles are very simple life forms based on chemistry, single-celled organisms with their enormous number of hypercycles are a significantly higher life form.

Living things need a boundary to hold their parts together. It is possible that the first living beings arose in small cavities in the rock between which chemical substances circulated. It was only much later that individual cells left the cavities and settled elsewhere. The first form of life was therefore not a single cell, but a habitat. The first biological form of life was therefore the biotope.



Living beings need to constantly take in food. This consists of chemicals and provide building material and energy. In order for life to arise, the necessary chemical substances such as sugar, fats and amino acids had to be available. Scientists have shown that for all important substances there are a number of ways in which they could have formed. A number of biologists therefore believe that there are living beings on many planets and moons in space.

Speciation
All living things live in a shared environment. They need to use certain things (called resources) from their environment, like food, water, and a place to live. These resources are limited, so when more than one organism tries to use the same resource, they end up in competition. When two living things compete for a common resource, one of them will eventually win and consume (or use) that resource. When something about a thing's body makes it better at competing for resources, we call that special feature adaptation. Since these adaptations can be passed from parents onto their children, as time goes on, these adaptations become more common within a population, or group of similar living things living together. This is called Natural Selection, or Evolution.

When a small group of living things (a small population) gets separated from the main population that they came from (like if they move over a mountain range or a river, or if they move to a new island so that they can't easily move back) they will often find themselves in a different environment than they were in before. This new environment has different resources and different competitors, so the new population will need different features or adaptations to be a strong competitor than what they had needed before. The original population hasn't changed at all, they still need the same adaptations as before. Over time, as the new population begins to adapt to their new environment, they start to look less and less like the other population. Eventually, after thousands or even millions of years, the two populations will look so different that they can't be called the same species. We call this process speciation, which just means the formation of new species. Speciation is an unavoidable consequence and a very important part of evolution.

The Earth itself was born 4 and a half billion years ago. At first, it was just a bunch of rock and water. There were no living things. But then, about 3.8 billion years ago, the first life was formed in the oceans. It was no bigger than a single cell, but that single cell was able to copy itself and form more and more cells. Over billions of years, as that one cell evolved, it became more and more complex. Eventually, about 1 billion years ago, the first living things with more than one cell were born. Many of the kinds of things that lived that long ago can't be found living in the world any more, because newer things have been better competitors and forced the older things to extinction, but we know they existed because we can find their fossils, which are traces of ancient living things buried deep in the rocks.