We know living things come from other living things. But how did the VERY FIRST living thing get here? Did it just pop out of nowhere? Can scientists make new life from scratch? If we took all the ingredients for life and put them on another planet, would life start there too after a long, long time?
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Imagine a pool of water, filled with chemicals. One theory has it being a shallow pool, and another has it in the ocean depths near geothermal vents. Either way, you have chemicals floating around in water, mixing into a wide variety of compounds. Now imagine that a particular compound is created randomly. The compound is nothing on its own, but combined with the next part, it becomes important. Before that, it is just another random collection of atoms.
Separately, lipids in the water form little bubbles. Not much different than soap bubbles, really. Now imagine many of these random compounds getting caught in these little bubble packages. Any number of combinations do absolutely nothing, but a specific set of random compounds get caught in the bubble, and something incredible happens.
These compounds, when separated from their environment (so the water can’t dissolve them), but with a way to take in energy (through the thin lipid barrier of the bubble) become able to reliably produce energy. Resources from outside are absorbed, the compounds use the energy to create proteins, and waste product is able to be expelled from the cell (lipid bubble). It becomes a self-sustaining system.
Then, again through random chance, the chain of compounds that produce the energy become replicable (see RNA replication). You now have growth. After enough replication, the cell divides and you have two identical copies producing energy.
At this point, you have a cell that can take in resources, use the energy from that to produce proteins that then go on to create more complex processes, expel waste products, and replicate. This all happened by random chance, and there were likely millions of combinations that didn’t have this result. It only took one. Slight changes during replication create differences, and some of them become beneficial. The beneficial changes replicate more often, and it becomes a trait.
This series of events continues, and eventually you get something that can reasonably be called unicellular life. Taking in resources, producing energy, expelling waste products, and replicating are all key definitions of “life”.
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