I only understand areas when presented in tennis court multiples.
And what happened to the London Bus as the SI unit of mass?
43 posts • joined 13 Jul 2018
You missed a bit. The "old" definition of species was used to describe the situation where two individuals could breed together and produce offspring which are themselves fertile. Hence why horses and donkeys are not considered conspecific. It all falls down of course when you learn that a very few female mules can be fertile, when mated to a purebred horse or donkey.
The situation in the avian world is much more complex and controversial.
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