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Re: Speciation rate



At 04:54 PM 3/26/99 +0000, Martin Human wrote:
>Thomas R. Holtz, Jr. wrote:
>
>>Some
>>possibilities to explain these include:  sexual dimorphism; two or more
>>species being present; one species with individual variations; one >species
>>with changes over time (on the hundreds of thousands of year scale).  
>
>
>I have a question(s) for the list (it may be a non-question):
>
>- Do species "drift" with time?  We understand that when new ecological
>opportunites present themselves we seem to see life-forms expand to take
>advantage of them, but what about a "stable" environment? 

According to at least one model, when a species is in a stable 
environment, its likely to increase in genetic diversity.  However,
the environment should include predator and prey ratios as well.
I suspect this is really a hypothetical question, that's just my
opinion.  

Mathematical models allow for chaotic stability, so a population
may increase and decrease in size predictably or even cyclically.
Such models can become more typically chaotic with small pertebrations,
but true stability is almost impossible (at least in the models).

>
>- What is the average "life span" of a species in a "stable"
>environment? 

I would guess indefinite.  Maybe I should ask what you mean by
stable?

>- Are "rates of evolution" equal for aquatic and terra life forms? 

The biggest factors would be the number of genes and the birth rates.
Unless radiation really is a factor.  I should probably leave this
one alone.  

-Randy

>- Are examples of "unchanged" species over millions of years confined to
>aquatic forms (ie does water act as a "buffer"?)? 
>- During the "explosive" phase (if such exists) is the rate of
>divergence apparently the same for all species (after K/T for example)?
>
>Has anyone done anything on this, or am I being obtuse?
>
>cheers, m
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