What are that collects on the surface of the earth is called

Asquirrel population lives in an area. over many years, a river in that area grows wider and stronger, eventually forming a canyon. the squirrel populations on the two sides of the canyon can no longer mate with each other and ultimately form distinct species. this is an example of

Darwin’s hypothesis about how life changes over time is now called?

How to farmers could ensure that they only grow white flowers