Just a strange thought on my part. Maybe evolution has a reverse element.
I bring this up because I was thinking about the vast proportion of living organisms that survive on CO2. CO2 is a infinitesimal portion of the atmosphere. It is four 100ths of 1% of the atmosphere. There is more than 1000 times as much oxygen as there is CO2.
So getting CO2 out of the atmosphere is significantly more difficult than getting oxygen which comprises nearly a quarter of the atmosphere.
Intermediate to land based and air based animals with their abundant supply of oxygen is the entire world of water creatures. Most of these creatures take in water to extract oxygen. They are extracting the oxygen from the tiny concentration of air that is dissolved in water.
How is it that so much of the world’s life is extracting bubbles that are dissolved in the water?
Life from an infinitesimal source in the atmosphere and an additional large segment of life must extract that atmospheric component from air dissolved in water?
This is what leads me to wonder whether there is a reverse element in natural selection that goes from very hard to very easy.
If you have thought about this question, please feel free to explain it to me.