Final answer:
Macroevolution is the subfield of evolutionary studies that looks at long-term evolutionary changes, encompassing broader scale changes over paleontological time like speciation and mass extinctions, in contrast to microevolution, which deals with shorter-term changes within a population.
Step-by-step explanation:
The subfield of evolutionary studies that focuses on long-term evolutionary changes is known as macroevolution. Macroevolution refers to the broader scale evolutionary changes that scientists observe over paleontological time. It involves changes that occur at or above the level of the species, generally over many generations, and includes phenomena such as the emergence of new species (speciation), the evolution of major groups of organisms, and mass extinctions.
In contrast to macroevolution, microevolution describes changes within a population's genetic structure, such as shifts in allele frequencies over a relatively short period. Modern synthesis is the overarching evolutionary paradigm that encompasses both microevolution and macroevolution, explaining how selection and other factors such as genetic drift, mutation, migration, and nonrandom mating shape the evolutionary process over time. The study of macroevolution is critical to understanding the large-scale patterns and processes that have shaped life on Earth.