GM>I would like to point out that
>predation is good. And God uses it to increase the number of species
>which can live on the earth.
>
>Consider the following:
>"Only a few experiments similar to Paine's have
>been performed and so one must be cautious about applying this conclusion
>to all communities."
Whether predator-prey relationships actually increase the number of
species living on the earth is a matter of conjecture at this point.
Actually, many biologists see the predator-prey relationship as existing
more in a state of long term equilibrium (mutually sustaining) within
biological communities.
One's world view can produce different conclusions from the Pisaster
experiment. Evolutionists would see the Pisaster study as showing that
predator-prey systems increase world-wide species diversity.
Creationists would argue that no new species developed at all, only that
a recombination of existing species occurred to fit changing local niche
conditions.
Since many predator-prey relationships are cyclical in nature, the
diversity issue is quite a fluid thing anyway.
By proposing that predation is "good" (and contributes to species
diversity), must one also accept the converse that the resultant
inter-specific prey competition (due to the lack of predators) is "bad"
(does not contribute to species diversity)? Do I hear a gasp from the
evolutionists in the crowd? I am willing to grant that both are merely
"different" pressures on the prey population.
GM >"There is some independent evidence, however that
>herbivores, which act on plants as predators do on their prey, may
>similarly increase the number of plant species that can live in a habitat. "
>"A similar process occurred in chalk grassland areas in
>Britain, when the disease myxomatosis caused the death of large numbers of
>rabbits; the resulting reduction in grazing allowed considerable invasion
>by coarse grasses and scrub. As a result many of these areas are much
>less rich in species than they were under heavy 'predation'."
This is a classic example of reporting the data to fit one's agenda.
Note the subtle use of the word "many". Evidently there are some areas
that are more rich in species.
Robert L. Smith, a noted ecologist and professor reported this same case
in his textbook Ecology and Field Biology, 2nd edition, 1974 in a much
more objective manner. In it he reports that...
"Although some early work by the English ecologist A. Tansley showed
that rabbits grazing on the chalk flora produced a richer diversity of
species, the real impact of rabbits was not noticed until after 1954. At
that time myxomatosis nearly wiped out the rabbit population, reducing
the predatory pressure on the grasslands. With the demise of the
rabbits, there was a spectacular increase in the growth of grass and a
profusion of perennial species whose existence had never been recorded.
But after the initial flush the number of dicot species declined, the
grasslands were dominated by a few species to the exclusion of others,
and the number of vegetative shoots of both grasses and dicots reduced
as the plants grew into taller, self shading vegetation."
Again, no new species developed only immigration by existing species to
fit new niche conditions. In fact, this study shows that predatory
pressures restricted the diversity of the plant community and its
inherent and immediate tendency toward diversity. It is the actual
post-non-predator diversity that may have given rise to its own demise
through plant community and succession pressures rather than the absence
of rabbits.
Actually, my wildlife biologist training stressed that you strive to
manage and increase the diversity in the plant community to affect the
predator (grazer) population for many game and non-game animals. From
this one might conclude that in many instances the diversity of plant
species contributes to animal diversity in a local setting rather than
the other way around. Often times, even with plant diversity present
there can still be a limiting factor that needs special attention. This
may not even be the food species but such things as nesting sites or
escape cover.
These concepts speak to the mutually sustaining relationships in many
biological communities. In actuality, a diversity of species-mix occurs
from one community to the next and is the result of local conditions and
the available species rather than evolutionary mechanisms.
The Strongylocentrotus case and the one regarding the Hawaiian
damselfish are similar examples of my previous point. The desire to
extrapolate these observations into evolutionary mechanisms is self
evident. Creationists would limit the interpretation of the results to a
simple reshuffling of existing species under different niche conditions.
They certainly do not demonstrate God increasing the number of species
living on the earth.
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Rv:4:11: Thou art worthy, O Lord, to receive glory and honour and power: for
thou hast created all things, and for thy pleasure they are and were created.
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Paul Durham
Oakland, Maryland
pdd@gcc.cc.md.us
to: IN:evolution@calvin.edu
cc: IN:GRMorton@gnn.com