Size Does Matter

Prerequisite: none

I had a curiosity for gigantic organisms. Gigantic, as in dinosaurs, eighteen meter sharks and five meter sloths. Then I came across the right book. Here are the highlights of John Tyler Bonner's book Why Size Matters: From Bacteria to Blue Whales.

First of all, we all love pictures. This book has tons of cute illustrations. This diagram compares the sizes of various species in the eukaryotic domain. Adorable, especially specimen number 10..

That is a tapeworm.

Some other awesome organisms introduced, such as the rotor flagellum bacteria. Just when you thought humans were cool for using wheels and axles, these bacteria were born with it!

And then some maths. Roughly. The little fishlike squiggle (∝) means "proportional to". This is a summary of general trends that organisms follow:

Some other trends are (diameter ∝ height) and (size ∝ distribution distance). In fact, most organisms seem to aim for a common size-distance ratio. That is very mind blowing.

This book also introduces the Reynolds number, defined as the ratio of inertial force and viscous force. It points out that although microorganisms appear to swim relatively fast with their rapidly beating cilia, that is not actually the case. If you were one of these puny germs, the Reynolds number would be extremely low as viscous environment has way more effect on your microscopic inertial mass.

And my very favourite, this graph:

Organisms of one centimeter appear to be the slowest in the race, while the two extremes of the size spectrum are incredibly fast. So you see, size does matter.