Which is the term that describes when the fossil record shows that two groups of organisms are related?

common ancestor.

Explanation:

when two groups of organism are related it means they share a common ancestry but may be they are not a direct parent but can relate to there far back generation.

Evidence from fossil's records are used to study that today how much organisms have changed themselves according to the environmental changes on earth. DNA and genetic codes mainly shows the shared common ancestry.

common ancestor