In the last essay we learned about organic compounds called proteins and DNA. Now we are going to try and piece together a method of getting a simple life form, a hypothetical bacteria-like cell kind of like the first living thing as part of the Theory of Evolution.
The piecing together begins with choosing a location. The first living cell came about on land, presumably in a puddle some where, or in the water somewhere in the ocean.
Now, exposure to the atmosphere poses a lot of potential problems. First of all, the oxygen we have in the atmosphere today is actually toxic to a lot of bacterial life. When it comes to O2, there are three types of microbes: anaerobic, facultative aerobic, and aerobic.
Anaerobic bacteria die when exposed to oxygen. It's toxic to them.
Facultative aerobic bacteria don't care. They don't need oxygen to live, but they aren't harmed by it, either.
Aerobic bacteria require oxygen to survive.
When it comes to bacteria types that make good candidates for the First Living Thing Ever contest, guess which type wins? The anaerobic bacteria. Every time. The Theory of Evolution assumes that Anaerobic bacteria evolved into Facultative Aerobic Bacteria which evolved to Aerobic bacteria. From there, photosynthesizing protists (like algae) and oxygen-requiring protozoans (like amoebas) were the next step on the evolutionary ladder. The first bacteria must have been anaerobic.
Ok, so no oxygen in the early atmosphere. That's ok so far, though, since the Theory of Evolution is based on the Nebular Hypothesis, which says that the earth formed from colliding dust and rocks as it revolved around the sun. There would be no source for the oxygen in the atmosphere until photosynthesizing creatures entered the scene anyway.
So - crisis saved, right? Wrong. Oxygen gas is not the only form of oxygen in the atmosphere. Oxygen also exists in the atmosphere as O3, or ozone. You can't have one without the other, so without oxygen, there's no ozone, and no ozone, no life.
Seriously. The ozone layer is a layer of earth's atmosphere that blocks out harmful light from the sun. The sun washes the earth in lots of different types of light: visible colors like red, blue and green; nice warm infrared rays; and some very harmful ultraviolet (UV) light rays. Many of the most harmful rays are deflected away from us by the earth's magnetic field (hello Aurora Borealis), but those UV rays can still get through. Thankfully, most of those are broken down by ozone gas in the ozone layer.
But once again, the earth's early atmosphere is not supposed to have oxygen. So it had no ozone. Thus, an organic compounds trying to organize themselves into a cell would have been killed by UV rays. Thus, literally every single place on the earth exposed to sunlight is off limits as a place where the first living thing came to be.
Well then. Let's try the ocean. But not just anywhere in the ocean - UV rays can still penetrate into much of the ocean's surface waters. No, let's go far and safe away, down to the bottom of the sea. Better yet, let's place it in the deep sea's hydrothermal vents. In some areas on the dark sea floor, there are black smokestacks releasing water and chemicals from deep within the earth. And at up to around 860 °F! They are also havens for weird life forms like rose-lipt tubeworms and chemosynthetic bacteria (i.e., they can make their own food from chemicals only, instead of requiring light like photosynthesizers).
These vents might be exactly what we're looking for. They're far away from sunlight and thus UV rays, and the vents are constantly shooting out elements found in organic compounds.
Unfortunately, problems arise here too. You see, many organic compounds, like amino acids, break down in water. We call this hydrolysis.
Dehydration reaction: a chemical reaction that links two molecules together by removing two hydrogen atoms and an oxygen atom (i.e., a water molecule).
Proteins are built with dehydration reactions. One amino acid loses a hydrogen (H+), and another loses an hydroxide group (OH-). Those two then combine to make water (H2O). So, take away a water molecule, and two amino acids are linked up. Take another water away, and now you have three linked amino acids. And on and on until you have a protein chain.
Hydrolysis: the process by which a molecule is broken down by adding water.
Add water to a protein, and the amino acids will go back to their unlinked, H and OH containing, states.
You won't get a protein chain the naturally construct itself under water. The scientifically observed process of hydrolysis would prevent that from ever taking place.
Final Essay: The Reactions of Life