Fossils in upper were younger than fossils in lower levels. Hope this helps!
According to the research, a molecular clock can be used to determine the number of differences in a specific DNA sequence of two species (c).
<h3>What is a molecular clock?</h3>
It is a tool that allows us to relate the divergence time or the time elapsed since the divergence of two current lineages from their common ancestor.
It is based on analyzing and comparing the genetic material of organisms to establish the number of mutations.
Therefore, we can conclude that a molecular clock can be used to determine the number of differences in a specific DNA sequence of two species (c).
Learn more about a molecular clock here: brainly.com/question/12145820
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A- non-native species can have positive and negative affects
