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Re: Big = Old = Advanced?
John Bois wrote...
> 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,
As we have discussed many times before, this is not neccessaily true.
If all or most of the eggs laid by most invertebrate species survived,
each generation could multiply the population of the species by hundreds,
thousands, or even millions of times. Most of the offspring are
expected to die. Think about sea turtles; I don't know how many eggs
are layed per clutch, but it is more then two. Yopu don't have to be
very good at math to realize that if most of the offspring survived,
the population would be exploding to the point that thier niche could no
longer support them, and there would be massive mortality. Don't cite
human hunting as being the sole reason why this isn't happening
either; sea turtles evolved this reproductive strategy long before we
This is getting back to the spectrum of reproductive strategies that
have been mentioned in this discussion before: K strategies, where a few
offspring are EXPECTED to survive in order to achieve reproductive success
(this is like betting a LOT of money on relatively low risk investment)
and r strategies, where large numbers of offspring are produced and it is
EXPECTED that most will die. This strategy is like regularly playing the
lottery (with slightly better odds); each ticket doesn't cost much, and
you only need one or a few winning tickets to make it worthwhile.
> culling going on. Laying more eggs would seem to be a fruitless
If the environment, by predation, illness or other factors, has
the capacity to kill X number of offspring, you want to produce MORE then
X number of offspring so enough will survive to maturity to continue the
> clutch/litter size. Compare Emperor penguin (3 ft. long and lays one egg)
Which it takes very good care of....
> with Bob-white Quail (11 in. long and lays up to 28 eggs).
Where a lot of the infants die...AND egg mortality is high...
Or Elephant (big and one offspring)
Which it takes very good care of.
Previously in this discussion, you suggested that r startegies make
little sense, because a parent would not feel complelled or obligated to
feed predators. This is missing the point; the predators will take as
much as they want, if they can. Taking really good care of your offspring
is only possible of you have few. The more you have, the more you are
spreading yourself thin defending them all, and therefore the more
predators will take. Or, looking at it another way, if the predators will
take a lot, produce even more.
Colorado State University
Fort Collins, CO