Sarah observed that different kinds and amounts of fossils were present in a cliff behind her house. She wondered if changes in fossil content occurred from the top to the bottom of the cliff. She marked the cliff at five positions: 5, 10, 15, 20 and 25 meters from the top. She dug out and removed 1 bucket of soil from each of the positions and determined the kind and number of fossils in each sample.
What is the Experimental gorup, What responded to the change, and what Deliberately changed ?
