the image shows rock strata from different regions on earth. which fossil in the strata would best serve as an index fossil? fossil would best serve as an index fossil.  f1  f2f3f4

It's F3, I got it right on my test.

F3

Explanation:

An index fossil is a fossil of an organism which lived at only one time during the evolutionary history. The index fossils are obtained from rock of one particular evolutionary time zone.  In the given image, F3 fossils are present in same strata or layer of the rock in all three regions. They are also not present in any other layer of any region. Hence. F3 would serve as best index fossil.

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs