Final answer:
Microevolution involves small changes within a species over short periods, whereas macroevolution encompasses larger scale changes that can lead to the formation of new species, occurring over geologic time. Speciation is a key aspect of macroevolution, often resulting from the accumulation of microevolutionary changes.
Step-by-step explanation:
Understanding Microevolution and Macroevolution
Microevolution refers to the changes within a species or population's genetic structure, such as variations in allele frequencies over time. It usually occurs over a relatively short period of time and can result in adaptations to a population's local environment. Examples of microevolution include the Grants' observations on Darwin's finches, where small changes in beak size and shape occurred over generations due to selective pressures.
On the other hand, macroevolution is the process that leads to the emergence of new species, occurring over geologic time. It involves larger scale changes and can be the result of the accumulation of microevolutionary changes over a long period. Additionally, macroevolution can be triggered by major environmental events that cause a significant and rapid shift in a species' evolution.
Speciation, the formation of new and distinct species in the course of evolution, is a core concept in macroevolution. It often occurs when populations of the same species become isolated from each other, as seen in the case of Darwin's finches. After extended isolation and distinct evolutionary paths, these populations may change enough that they can no longer interbreed, thus forming new species.