Jagged Environment
Evolution of cell membranes
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Jagged EnvironmentEvolution of cell membranes |
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Mass extinctions |
Oxygen provides stress to cell membranes, as it did to the oil membranes of primitive clay-cells. Initially this would have led to antioxidants, to protect, to extend the lifetime of, these fragile primitives. If the lifetime is too short, the simple species rapidly fails and dies; therefore the introduction of protection was the vital and key initial stage in Evolution. But the lifetime cannot be too long either - nothing can live forever - or Evolution stops, there being no further development. So there is a balance. Evolution is implicit to life, and forcing it is sometimes beneficial; but if it is too forced, the turnover of cells is too fast for life to be sustained. Cell turnover (programmed cell death - apoptosis) is central to Evolution (co-operative advantage), since it allows the pre-existing cells to be replaced by more developed versions, better able to co-operate. This aim is ensured by a background level of steady, but limited, damage, which accumulates. So in modern cells, not all oxygen damage is intercepted by antioxidants; iron is released at low level from its storage compartments, reaching DNA, as part of the mechanism which ensures that cells will die eventually. Considering their vulnerability, the rapid development of antioxidant levels - i.e. of maximum protection - in primitive clay-cells was a great advantage, but even these were required to turn-over and to be reproduced. In the complex cell structures achieved by higher evolution, as in animals and plants, achieving maximum protection would be a disadvantage to the species, which would then have only limited capacity for evolution. To achieve maximal benefit for species, sophisticated mechanisms for self-destruction became evolved into cells during their higher development. Copyright © 2001 Chris James Last updated 12 March, 2005 |
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