[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Pollen From Permian/Triassic Extinction Show UV Induced Mutations
----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Monday, October 20, 2003 9:30 PM
> On Sun, 19 Oct 2003, Jaime Headden wrote:
>
> > John Bois (jbois@umd5.umd.edu) wrote:
> > (Predation/competition extinction models) would
> > seem to make sense in regards to an extinction event on a
> > population, rather than a global mass extinction of a percentage
> > (however small) of a given range of species. Climate changes, or
> > disease, or other natural disasters or alterations can effect a wider
> > range of species...
>
> I don't think this is an accepted assumption. Certainly it would be true
> if species were isolated from each other. Is this the case? If not, the
> evolution of new traits should be expected to have profound effects on
> species composition.
How profound is profound (what's suggested in the book of JP II is far too
profound), and what could those new traits have been at the P-Tr boundary?
----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Monday, October 20, 2003 9:57 PM
> > (Prey can grow out of highly preyed-upon size classes when) they grow
> > as fast as most extant mammals and birds. Such growth speeds
> > are rather unexpected for end-Permian fauna. Besides, what could that
> > predator be that would have been capable of exterminating itself? (I'm
> > talking about the whole globe and not just California, pardon the pun.
:-> )
>
> What are the factors that contribute to growth rate? Parental care,
> metabolic improvements...
Hm... and diet. And what the hormone glands think of it, but that's
variable. I can't think of more at the moment.
> are such new traits off the table when
> trying to account for radical changes in speciation?
I see no reason to assume that any such trait evolved right before the P-Tr
boundary. The taxa suspected of suchlike are all considerably older. And
many small ectotherms, like procolophonids, survived the boundary quite
well. What are the big taxa that apparently survive longest in the Karroo?
Is there any (rather certainly ectothermic) pareiasaur among them?
And why do you assume radical changes in speciation, instead of radical
changes in extinction? I can imagine a mass extinction resulting from
extinction rates jumping up alone, while speciation rates staying high as
ever. (And increase after the extinction, when so many ecological niches are
free, but that's not a part of the question.)