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An event which a lineage rapidly diversifies in response to an opportunity is called:

A marine regression is characterized by ____.

We now know that most genetic variation in populations is caused by:

Populations that have similar individuals that can interbreed and produce fertile offspring are called:

A particular order of fossils in Silurian rocks in eastern Ohio is nearly identical to an order of fossils in Silurian rocks in western New York.  Even though they are from two different locations, they are in fact similar in age.  Choose which principle best supports this conclusion:

A half-life is the amount of time required ____:

If a radioactive isotope has a half-life of 50 million years, and a rock sample contains 1/8th of that isotope remaining overall, what is the age of the rock from which the sample was taken?

  A geologist observes an outcrop of sedimentary rocks composed of shale and sandstone with several igneous bodies cutting through the layers.  To determine age relationships, which principle best explains this example?

Bodies of rocks that are thick enough to be mappable with distinct upper and lower boundaries are officially designated as:

A guide fossil has some or all of the following desirable characteristics except: