Question

1. which of the following best defines an index fossil?

the fossilized remains of an organism that was among the very first to exist on earth
the fossilized remains of an organism that is exceptionally well preserved compared to other fossils
the fossilized remains of an organism that is commonly found in a specific, local geographical area, but rarely found elsewhere in the world
the fossilized remains of an organism that is useful for dating and correlating the strata in which it is found due to its wide geographic distribution and short existence in geologic time

Explanation:

Index fossils are used for dating and correlating strata. They have wide geographic distribution and short existence in geologic time. The first option is about earliest organisms (not index fossils). The second is about preservation (not index). The third is local (index fossils are widespread). The fourth matches the definition of index fossils.

Answer:

The fossilized remains of an organism that is useful for dating and correlating the strata in which it is found due to its wide geographic distribution and short existence in geologic time.