> 1. A mechanism that can make substantial genetic changes in step wise fashion.
> 2. The existence of a gene trajectory path from animal A to animal B with
>each change being large and benficial enough to modify reproduction rates for
>the animal with the genetic benefits.
As long as accumulated mutations do not decrease the reproductive success
so much as to cause it to die out, they can persist. This depends strongly
on how tough the selective pressure is. If everything is easy,
disadvantageous mutants can survive because there is little pressure. If
the environment is so bad that everyone is in trouble, disadvantageous
mutants may be able to survive because they are not competing against other
individuals but are rather matched against the environment. This fits the
pattern of gradual and punctuated patterns in the fossil record fairly
well, to the extent that it has been examined. Times with low competition
(such as just after a mass extinction) or very stable conditions tend to
show rapid evolutionary radiation or gradual change. Times with moderate
environmental variation tend to show stasis punctuated by rapid shifts.
> 3. A quickly acting mechanism to make this happen which is triggered by
>something to be identified because the fossil evidence is for stasis with
>punctuated and rapid changes.
One rapid mechanism for genetic change comes from the role of heat-shock
proteins. Normally, they stabilize other proteins. However, they transfer
over to emergency use in times of severe cellular stress, such as heat
shock. When they abandon their normal stabilizing function, mutations in
those proteins that had been covered by the work of the heat-shock proteins
may come into play and be selected for or against.
David C.
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