Sunday, November 09, 2008

Population Doubling

As I am preparing for my talk, I am doing some intense demographic analysis of my rotifer data set. One interesting factoid I have calculated is that the population doubling time, assuming I could keep an infinite number of rotifers and didn't have to get rid of any, is 28 hours.

A related calculation: If I started with one newly hatched rotifer and let the population grow (with my average age-specific reproductive rates and death rates), after one month I would have 159 million rotifers.

The average volume of a rotifer is about .001 cubic millimeters. A million of them pressed together makes one milliliter. A billion makes a liter. 10^27 would be a cubic kilometer. Earth's oceans have a total volume of 1.347*10^9 cu km, meaning I would need 1.347*10^36 rotifers to fill them completely with no space between rotifers. At the demographic rates they maintain in my lab, assuming I didn't cull any, this would take 138 days.

I only have time, container space and staff to keep track of 450 rotifers at a time, so I end up culling a significant portion of my population every day.

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