How would scientists know if population were increasing or decreasing over time

Select the correct answer from each drop-down menu proteins are

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 tool could you see a plant cell? a. a filter b. a microscope c. a microwave d. an electromagnet