Answer:
How the landscape changed over time
Explanation:
These fossils are very useful for us because we can use them to date the layers of rock that they are found in. Fossils that can be used in this way are called index fossils, and rock layers with the same index fossils in them can be correlated. Not my answer, link here for full
http://peter-mulroy.squarespace.com/correlating-rock-layers/
Life liberty property and the pursuit of happiness
Nervous system
Circulatory system
Cardiovascular system
