Title Author Date

Noah's Ark Rossow, Amiel Apr 25, 2005

Hi, Mike:

Thanks for taking time to reply. I have never been a biologist (and never petended to be one) and had no idea of the distribuition of
animals' body mass you described. Oddly, first you wrote that it is (roughly) a linear dependence, but now you say it is "a quarter-square power law." I must admit that I don't understand your expression. What do you
mean by a "quarter-square power"? Please keep in mind that you owe me no reply and I feel uncomfortable taking your time, so if you will pass this messasge without a reply, I'll understand.

Cheers,

AR

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Title Author Date

Noah's Ark Elphick, Michael Apr 25, 2005

Hi Amiel,

I too have searched the internet and the "quarter-square power" relationship I found was in some internet college biology notes.
Unfortunately I'm not on that computer anymore, so can't give you the reference, but I'm now back on the original one and can give you this link: http://faculty.plattsburgh.edu/thomas.wolosz/howmanysp.htm.

When I stated that there was an approximate linear relationship, I was wrong. You can see on this site that they have made a log/log plot, which is a typical biologist's trick to get a straight line out of anything ;-) !!

As Wesley states, biology does not have the precise relationships implied by the "quarter-square power". A similar (and interesting!) relationship exists between body surface area, mass and metabolic rate: http://webusers.xula.edu/cdoumen/CAP/Metabolism3.html.

Wesley has included microorganisms in his grouping of species (no one knows how many species of bacteria there are - anything between one million and half a million) so this would skew the relationship for the very smallest organisms. With regard to Noah's Ark, I was talking specifically about beasts of the field and animals that creepeth along the ground etc. God didn't tell Noah he had to save the microbes!

I think you can see that, whatever the *exact* mathematical relationship might be, there are many more species of smaller animals than larger ones - so my argument stands. A horse is definitely not representative!

Regards to you both,

Michael.

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Title Author Date

Noah's Ark Rossow, Amiel Apr 25, 2005

Dear Mike,

I must apologize - my curiosity has led to that exchange of messages - not the first time - and I had no intention to argue against your
horse-related comment. You are probably right in that the mean mass of an animal is somewhere to the left of the horse's mass on the "number of species vs body mass" plot. However, as you said, this can't change the overall conclusion regarding the implausibiliity of the bibliical story if all the food mass is accounted for, etc, so if creos will try to dispute my
conclusion based on the argument you have offered, I'll be able to counter it. None of them ever mentioned my essay since its posting in 1999 and most probably they will not do so in the future. Anyway, thanks for your messages
and best wishes.

AR.

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Title Author Date

Power law Elsberry, Wesley R. Apr 25, 2005

There are certainly some general scaling trends in biology concerning size and metabolism that may be described in terms of "power law" or
"power function". But these are not exact relations. Biology is usually a lot messier than people coming from physics or chemistry like to admit.

So far as I know, there is no simple relation between "body size" and "number of species", and certainly not a generally known result with
scaling of the sort stated by your correspondent.

Wesley

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