What is an index fossil?
A. a fossil of a footprint or other trace made by an organism
B. a fossil in igneous rock
C. a fossil of an organism from a species that did not live for very long
D. a fossil left during a mass extinction event
C. a fossil of an organism from a species that did not live for very long
To determine the correct answer, let's break down the options:
A. A fossil of a footprint or other trace made by an organism: This definition describes trace fossils, which are not index fossils.
B. A fossil in igneous rock: Igneous rock is formed from volcanic activity and does not typically contain fossils. Therefore, this option is not correct.
C. A fossil of an organism from a species that did not live for very long: This is the definition of an index fossil. Index fossils are typically from species that had a relatively short existence on Earth.
D. A fossil left during a mass extinction event: While a mass extinction event can lead to the preservation of many fossils, this definition does not specifically describe index fossils.
Based on the analysis, the correct answer is C. A fossil of an organism from a species that did not live for very long.
So, an index fossil is a fossil of an organism from a species that had a relatively short existence on Earth. These fossils are useful for dating and correlating the age of rock layers, as they provide a distinctive time marker.