Replication vs. Metabolism First

This week in AP Bio, we did a reading for homework and took notes on either Metabolism First or Replication first hypothesis for evolution on earth. After the reading, we came into class and received a paper that basically said that what we were arguing was wrong and why the other was right. During a debate that was really more of a class wide discussion, we argued for one or the other using points from the documents to back us up.

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Main idea (Replication first): Replication first, also known as the RNA World Hypothesis states that long ago, RNA was created from ribonucleotides that were accumulated on earth. RNA could accurately copy itself over and over. The more RNA that was created, the more errors would occur, causing each offspring to be slightly different. Life was able to evolve because ribonucleotides attached to specific amino acids making proteins. Science has proved that this theory makes sense because we can create sugars and these nucleotides using the gasses and the conditions on earth, using the simple building blocks. We can skip the creation of building blocks and go straight to creating the nuleotides (which are linked to RNA). Clay Montmorillonite (which is only found on earth) can serve as a catalyst, it holds nucleotides and RNA. RNA replication was argued to be improbable because of how long it would take and how unstable they would be, but this had plenty of time, millions of years even to create stable and evolved life forms.

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Main idea (Metabolism first): Also known as the Iron-Sulfur world Hypothesis, claims that mineral catylists in deep sea hydro-thermal vents could promote evolution. These sites produce Hydrogen Sulfide (H2S), it can react with iron sulfide minerals and catalyze a series of chemical reactions creating a reverse Kreb Cycle. The Kreb Cycle is a series fo chemical reactions that take place in all aerobic cells today, it extracts energy out of organic molecules taking in CO or CO2 and reduces it using electrons to form complex organic molecules. The end products from these reactions become the start for the next one, it is a self sustaining process so it can happen constantly. The organic molecules formed will accumulate and some will form membranes, the membranes can protect the catalyst and separate it from the rest of the ocean and form a cell. Because this is self sustaining, it could happen many times explaining cell structure.

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At this point in time, it is hard for me to argue towards one or the other because I am not very educated as far as how this truly works. If I had to choose, I would choose the RNA world hypothesis because RNA replicating itself with error occurring over millions of years makes more sense to me than underwater vents creating a self sustaining cycle of cell creation that turned into organisms. To have better and more valid arguments, I would need to read more into these topics.


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