Here's a breakdown:
* Large-scale: It involves significant changes in the diversity and complexity of life, like the origin of new species, major transformations in body plans, or the extinction of entire lineages.
* Long periods of time: Macroevolutionary processes unfold over millions or even billions of years.
* Above the species level: It examines evolutionary changes happening at the level of genera, families, orders, classes, phyla, or even kingdoms.
In contrast to microevolution:
* Microevolution refers to evolutionary changes within a population, typically on a smaller scale and over shorter timeframes. Examples include changes in allele frequencies, adaptations to specific environments, or the formation of new varieties within a species.
Important notes:
* There is no distinct "macroevolutionary mechanism": Macroevolutionary changes are ultimately driven by the same mechanisms as microevolution, namely natural selection, genetic drift, mutation, and gene flow. However, the cumulative effects of these mechanisms over long periods and across many generations result in larger-scale changes that are considered macroevolutionary.
* The distinction between micro and macroevolution is not always clear-cut: Some evolutionary biologists argue that it is more helpful to view evolution as a continuous process, with no clear distinction between the two scales.
* "Macroevolution" is often used in a more general sense: It is sometimes used to refer to any evolutionary change, regardless of scale.
Therefore, understanding macroevolution requires understanding the intricate interplay of evolutionary mechanisms over vast timescales, resulting in the diversification and complexity of life we observe today.