They found one thing that remained constant among all biological species: the cycles of growth and decay.

So the brain looks at this and thinks "biological species."

A biological species is a group of individuals which can breed together (panmixia).

Speciation is the evolutionary process by which new biological species arise.

Any biological species will, on a long enough time- scale, become extinct.

Nevertheless, the possibility that some of the above are separate biological species cannot be discounted at present.

Space can provide for an unlimited increase in population and potentially the introduction of new human biological species.

And this is true not only of biological species.

I applaud the various measures relating to standards and biological species.

This gives different biological species the ability to respond to situations with a built-in response mechanism.