<span>The question is providing us with the following scenario:The frog population in the Amazon basin varied. Every 500 years, there was a mutational change leading to speciation. In between, the population remained the same with no observable changes. This pattern of microevolution is called punctuated equilibrium. This pattern is distingushed by long periods of lack of change, followed by a sudden and often extreme change, and followed again by a period of a lack of change. </span>
Most fossils form when living things die and are buried by sediment that hardens into rock over a given time.
Pulmonary and systemic circulation.
For the answer to the question above, I believe the answer is "Tertiary Period"
<span>The Tertiary Period marks the beginning of Cenozoic Era. It only began 65M years ago and lasted more than 63M years, until 1.8 million years ago.</span> I hope my answer helped you. Have a nice day!
