Self-Check: Faunal Succession
A key to understanding faunal succession is to realize that many organisms exist on Earth for only a certain time and then disappear or become extinct. Their fossils are found only in rocks from a certain time, and rocks of different ages contain different fossils. Using superposition, we know that rock layer 3 is older than rock layer 4. Thus, the fossils in layer 3 are older and more primitive than those in layer 4 and so on. The most advanced forms of life are found in the younger layers, while less complex organisms are found in the older layers. Answer the questions below to review faunal succession. After typing in your answer, you can click to see a sample answer.