I have followed the David Attenborough series on 'First life' and heard, that an increase in the amount of oxygen in the atmosphere, as it took place just before the Cambrium, is generally favorable for life and also enables the evolution of larger organisms. Why is that so? Is it because aerobic respiration had a better conversion rate to energy?
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5$\begingroup$ I think you are right - O2 allows more energy to be released from fuels in less time, allowing warm-blooded animals to develop and thrive in colder climates. However, this was only possible through large-scale adaptations to eliminate oxygen radicals in the body. Oxygen is about the most reactive compound around and therefore potentially lethal. Hence 'generally favorable form life' seems to be an invalid statement. In fact, you could envision the abudance of plant life killing life instead of supporting it. $\endgroup$– AliceD ♦Commented Mar 9, 2015 at 10:31
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2$\begingroup$ @AliceD Indeed, see en.wikipedia.org/wiki/Great_Oxygenation_Event. $\endgroup$– augurarCommented Mar 11, 2015 at 5:16
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Because it's favorable for the process of aerobic respiration which requires O2 to produce ATP, which is the little power storage unit.
With a bigger concentration of O2, it was possible to produce more ATP, should you evolve in that direction and you needed that constraint to be removed.
