In math, there are special numbers, like Pi (3.14159...) and e (2.71828...). In chemistry, there's numbers like avogadro's number (6.0221413e+23). For example a circle can be defined in terms of 2 * Pi.
Are there any significant constant numbers in biology that define the shape of an organism (ex: mammal)? I'm talking about stuff like shoulder to hip ratio or length of an organism, etc?
Here's an example that came to mind - different fetuses developing into different organisms. Is there any constant that is the same for these at some stage of development? Like the ratio of head to tail?