why we breathe oxygen and not something like carbon dioxide or nitrogen?
In: 40
Like billion years ago, with the evolution of photosynthesis, that is, take CO2 from air (in CO2 rich atmosphere, where there was never any O2) and use sunlight and water to change it into sugar and release O2.
Happened for millions of years, now there’s a lot of O2 in the atmosphere but since there was never any O2 before this time, all the life forms (mostly bacteria) depended on CO2 for “food” and survival.
O2 can turn into a different forms as it is relatively unstable and form free radicles(which is harmful and causes ageing and mutations, etc), hence anaerobic(that depended on CO2 and not O2) life forms slowly died out.
Now this one very very ancient bacteria might have survived in these conditions and mutated might have even started to use this abundant O2 in air for food. By basically using O2 to make H2O it made a molecule called ATP which had a lot more energy (around 15 times more) than the previous bacteria which couldn’t use O2.
When you have extra energy(more money, can buy more expensive things), you can carry out more energy consuming life processes. And this bacteria might have been incorporated into a larger cell in a symbiotic relationship with it, and today we call it the mitochondria.
And then, evolution kept things going, structures and chemicals sensitive to O2 start developing and the rest is history.
Hope it helps, feel free to ask questions.
Edit why couldn’t they use nitrogen? Because carbon and nitrogen are relatively stable forms and don’t readily react with stuff, as opposed to oxygen which needs to 2 more electrons to be reach stable form, hence it has tendency to accept electrons more easily and hence react more easily.
Latest Answers