B. What are the units for the atomic radius?

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

Which could be a pathway of food through an ecosystem

Some substances but not other can cross the (blank) membrane of a cell