sexuality & Trees of Life

B. J. Tindall bti at DSMZ.DE
Thu Nov 16 09:01:19 CST 2000

Ken Kinman wrote:

">     However, I think it is **extremely** misleading to say that sexual
>reproduction is limited to a "small section of organisms".  In terms of
>species diversity, far more species are sexual than are asexual, and far
>more biologists study sexual organisms than study asexual ones."

I thought someone might say this. This is an arguement based solely on the
fact that zoologists and botanist have a vast list of species which have
accumulated since primitive man first started to recognise the differences
in different animals and plants. Even Linneaus had a wealth of data to work
on. The study of prokaryotes is rather recent, lets say 100 years. If one
takes a walk through a tropical rain forest then one quickly picks up all
the plants, birds, insects etc living there with the naked eye, but
everyone misses the diversity of prokaryotes present. Very few people seem
to take into consideration that chloroplats and mitochondria are derived
from prokaryotes and are as diverse as the eukaryotic cells which harbour
them! The arguement is based on current statistics, which says we have
named X million species of eukaryote, but only X thousand species of
prokaryote. The real question is what really is out there, and this is
where various sets of data indicate a fantastic untapped prokaryotic
diversity (not just genetic data). These are points raised by both Mayr and
Woese, but they both present arguements which do not really address
eachother's point of view. Diversity is represented by more than the
diversity of colours in butterfly wings. I fully accept the amazing
diversity in eukaryotes, reflected in their morphology, but one cannot
sweep prokaryotic diversity under the carpet. True eukaryotes are
morphologically diverse, but then they are much more conservative in other
aspects such as chemistry, biochemical pathways, areas in which prokaryotes
excel. Accepting one aspect of diversity does not mean that the other
should be ignored.
Brian Tindall

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