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Origin of Life
Life is defined as a chemical system capable of transferring its molecular information via self-reproduction and of evolving.

The three ingredients needed for life:
Scientist all agree that liquid water is essential for life to evolve and survive. This is because water allows simple molecules to mix together and react to form more complex stuff. The chemical building blocks that are needed are: carbon, oxygen, hydrogen and nitrogen. And in order to drive the chemical reactions an energy source is needed.

Figure: Amino acids, the 'building blocks' of life, may form in dust grains in the space between the stars. (c) ESA 2002.

The simple molecules mixed to form more complex molecules (amino acids) in the seas of the early Earth, often called the 'primordial soup'. The energy that was needed, might have come from lightning storms or from hot springs underwater. Amino acids came together end-to-end and formed proteins, larger chain-like carbon based molecules. DNA consists of purine or pyrimidine. DNA has the unique capability that it can reproduce itself. It carries code to make a living creature.

Not all scientists agree that life evolved from the primordial soup. Some think that life might have been delivered to Earth by a comet from space.

Continue with Chemistry of Life