|MadSci Network: General Biology|
Dear Javier, Yes, there is indeed an inverse relationship between size and population density. In general, small organisms attain greater population densities than do larger species. But, as is usually the case with such biological "laws", this too is somewhat controversial. The following article will tell you more about it. Marquet, P.A. Invariants, scaling laws, and ecological complexity, Science, Volume 289, pp. 1487-1488 (2000). If you want more technical detail about scaling or allometric relations, I recommend these books. Calder, W.A. Size, function & life history. (Harvard University Press, 1984) Dover Publications, 1996. Schmidt-Nielsen, K. Scaling: why is animal size so important? Cambridge University Press, 1984. Burton, R. F. Biology by Numbers. Cambridge University Press, 1998. The last book by Burton gives a good elementary introduction to the mathematics of power laws. I doubt that there is a database that gives the weights and populations (in a given area, of course) of all the known species. I also don't know if anyone is actually counting the number of species that have been described. Why don't you check out the links at the following address? http://www.biosis.or g/free_resources/index.html Regards, Aydin Orstan
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