Re: Big = Old = Advanced?

[Dinogeorge@aol.com]

In a message dated 97-08-24 11:46:04 EDT, jbois@umd5.umd.edu (John Bois)
writes:

<< While I agree wih Dinogeorge's main point (taxa that lose small
 species become extinct), I take issue with this mechanism.  Creatures lay
 or deliver the maximum number of offspring they can as long as those
 offspring have a reasonable chance of success--excess capacity, then,
 would be better used for future reproduction or assuring greater success
 of current production (parental investment). One would think a saurapod
 could lay much bigger clutches (and, therefore call 18 a small number).
 But, given that fecundity determinants of those creatures were unique and
 unknown, claims of relative size are meaningless.  What we can say, and
 Greg Paul has said it, is that if all the offspring of a saurapod
 survived she would have  produced upwards of 400 adult saurapods in her
 life. Obviously, as Betty C. and Tracy Ford have noted, there is gross
 culling going on. Laying more eggs would seem to be a fruitless
 enterprise.  
        In addition to this, size _per se_ has nothing to do with
 clutch/litter size.  Compare Emperor penguin (3 ft. long and lays one egg)
 with Bob-white Quail (11 in. long and lays up to 28 eggs).  Or Elephant
 (big and one offspring) with House Mouse (small with up to 11 offspring). >>

I don't know of any large mammals that have large litters, which is what I
was thinking of when I noted that large animals tend to have smaller litter
sizes. Now that I think about it some more, there's no basis for
extrapolating this observation to dinosaurs or other large egg-laying
animals.

But litter size certainly has an effect on the potential for diversification.
If in any given generation one kind of animal delivers one or two offspring
and another delivers one or two dozen, the chance of a mutation reaching the
gene pool has to be greater in the latter animal simply because it has more
"tries."