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Origin of life

Origin of life

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When was Earth formed?

Origin of life

Think of planet Earth - A blue and green globe, full of people, plants, animals and microorganisms. The Earth is home to so much life that it’s hard to imagine it without any. Let’s visit Earth four and a half billion years ago, shortly after it was formed. There is no life here yet. It’s extremely hot and water only exists as gas.

The surface is constantly bombarded with asteroids, and large areas are covered in magma. But there are molecules of oxygen, hydrogen, carbon, nitrogen, sulphur and phosphorus - the very basic building blocks of larger molecules that make up - life. 500 million years later and the surface of the planet is cool enough for water to condense and form oceans. For the first time ever, the conditions are suitable for life to form. The liquid water is a great environment for the basic molecules to mix.

But just water and basic molecules mixing together aren’t enough for life to be created, there needs to be an energy source too. Luckily, there are plenty around us! There is radiation from the Sun and electrical energy from lightning. With the energy provided, basic molecules can react and form more complicated molecules and compounds, from amino acids to proteins and fatty acids, and eventually even DNA! Now we’ve arrived at a time, around 3.9 billion years ago, when scientists think the first life forms started to exist.

Proteins, fatty acids and DNA come together to form more complex structures - such that can replicate, carry information and exist on their own. And this is where natural selection comes in! The ones that can replicate faster and exist for longer, continue to exist, while the other ones disappear. This is a theory of how life began, and it’s called GRADUAL CHEMICAL EVOLUTION. Now let’s go to a time a bit closer to ours.

It’s 1953 and two scientists, Miller and Urey, decide to test the chemical evolution theory. They build a machine that recreates conditions of the time when life could have formed on Earth. The machine looks like a circle of tubes connected to each other. In it, there’s water and a mix of gases that were present on the “early Earth”. There is also a chamber where electrical energy is applied as an energy source for chemical reactions.

After one week, Miller and Urey discover that they created molecules of amino acids, sugars and fatty acids - the building blocks of life! In almost the same way as we think molecules formed about four billion years ago. Although we have some idea of how the first molecules necessary for life have formed, we are not sure what happened next to create cells and finally organisms. The truth is that no one really knows how life formed on Earth. But what we do know, is that life on Earth has been evolving for billions of years, and we don’t know of any other life like it in the whole universe.

We should protect it at all costs.