O2 bugs bugs

[Steve]

Something about this (http://www.msnbc.msn.com/id/6901581/) doesn't make sense to me. Why would the evolutionary process result in creatures for which an excess of oxygen is deadly?

There are arguments and evidence that, hundreds of millions of years ago, if not more, the earth's atmosphere was greatly lacking in oxygen. I can see organisms developing in such an environment where their metabolism would require very little, if any, oxygen.

But that was hundreds of millions of years ago. Surely evolution would have selected for insect species that can handle the normal oxygen levels present in the atmosphere. After all, every other living thing, except anaerobic bacteria, have no troubles with oxygen levels. It makes no sense that insects would.

[Techie2000]

Steve,

The reason is because these bugs have already "adapted" to the environment via the ability to hold their breath a long time, so they survive. The ones that can't hold their breath were the ones killed off by natural selection.

[MorWired]

But that was hundreds of millions of years ago. Surely evolution would have selected for insect species that can handle the normal oxygen levels present in the atmosphere. After all, every other living thing, except anaerobic bacteria, have no troubles with oxygen levels. It makes no sense that insects would.Maybe I'm missing a subtlety here, but too much oxygen is a problem pretty much across the board.
.http://devweb3.vip.ohio-state.edu/Materials/PDFDocs/health-p/oxygen-level.pdf

Is there any problem if I use too much oxygen?
Too much oxygen can damage the cells inside your lungs. Also, if you have too much oxygen, your brain may not send out signals for you to breathe. For most people, when carbon dioxide starts to build up in your body, the brain signals to take a breath. The brain for a person with COPD (chronic obstructive pulmonary disease) gets used to a little extra carbon dioxide because the lungs have a hard time getting rid of it. If a person uses too much oxygen, the carbon dioxide levels may not trigger the brain so the brain may not signal to breathe as often or as deeply as needed. Taking fewer or less deep breaths is called hypoventilation (hi-po-ven-ti-lat-tion).

To prevent problems with too much oxygen, your oxygen levels are adjusted based on your pulse oximeter or ABG readings. Ask your doctor before making any changes in your oxygen therapy.

Oxygen Therapy Extra oxygen can help your oxygen level stay in a good range. This means less damage to your heart and brain cells and lower blood pressure in your lungs. If your doctor prescribes oxygen therapy, wear it.