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The fossil record provides a visual timeline of evolution and speciation for many organisms. Some fossil lineages show a species changing gradually over time, with numerous small changes visibly accumulating over time. Other species appear suddenly in the fossil record and then seem relatively unchanged for long periods of time.

Which of the following explains this pattern of evolution and absence of intermediate forms in the fossil record? Select ALL that apply.


Thousands of years are often compressed into relatively small layers of rock strata.


The fossil record does not preserve evidence of all traits equally well.


Some fossils are difficult to find.


Most speciation occurs very quickly.

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