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.