Basic Definitions of Macroevolution and Microevolution

Biology Texts, Popular Books on Science, Scientific Reference Works

Because the distinction between macroevolution and microevolution is fairly minor, you won't find the terms defined and separated in every science book — and not even in every biology text. You don't have to look too hard and too far to find the definitions, though, and it's important to note that macroevolution and microevolution are defined fairly consistently across many different types of scientific resources.

Collected here are definitions from three different types of books: basic biology text books like you would find in high school or college biology classes, introductory books on evolution that are intended for general audiences outside of school settings, and basic reference works (dictionaries, encyclopedias) on either science generally or some facet of biology specifically.

 

Microevolution & Macroevolution in Biology Texts

Quoted here are the definitions of evolution which high school and college students are exposed to when they take biology classes.

macroevolution Evolutionary change above the species level, including the appearance of major evolutionary developments, such as flight, that we use to define higher taxa.

microevolution Evolutionary change below the species level; change in the genetic makeup of a population from generation to generation.
Biology, 7th ed. Neil A. Campbell & Jane B. Reece

macroevolution A vague term, usually meaning the evolution of substantial phenotypic changes, usually great enough to place the changed lineage and its descendants in a distinct genus or higher taxon.

microevolution A vague term, usually referring to slight, short-term evolutionary changes within species.
Evolution, Douglas J. Futuyma

According to the theory of common descent discussed in Chapter 8, all modern organisms descended from a common ancestral species. This evolution of one or more species from an ancestral form is called speciation, and the process of speciation is often referred to as macroevolution. ...

Isolation of the gene pools of populations may also occur even if the populations are living in physical proximity to each other. This appears to be the case in populations of apple maggot fly, a species that provides one of the clearest examples of macroevolution “in action.”
Biology: Science for Life, Colleen Belk & Virginia Borden

It's interesting that Futuyma makes a point of saying that microevolution and macroevolution are "vague" terms — that they don't have clear, specific boundaries that would make it easy to tell not only when they are occurring, but more importantly where one ends and the other starts.

 

Microevolution & Macroevolution in Popular Books

Most people aren't likely to use or have access to the text books quoted above; if they are going to learn about evolution they are more likely to get a book for general audiences like these.

macroevolution evolutionary changes that happen over very long periods of time. This usually refers to the development of large new branches of life, such as vertebrates or mammals.

microevolution evolutionary changes that happen on a small scale, often within a single species, such as a change in the frequency of a particular allele within just a few generations
Evolution: The History of Life on Earth, Russ Hodge

Biologists customarily divide the processes of evolution into three broad categories. Microevolution refers to changes that occur within a single species. Speciation means division of one species into two or more. And macroevolution refers to the larger changes in the variety of organisms that we see in the fossil record. We will begin with an overview of evolution as a whole.
Evolution: A Beginner’s Guide, Burton S. Guttman

Guttman's explanation separates speciation from macroevolution even though most explanations of macroevolution include speciation within it. This reinforces Futuyma's point about the vagueness of the concepts: if it's not clear whether speciation is part of macroevolution or not, how can we justify drawing a sharp, bright line between macroevolution and microevolution? What, really, is the difference?

 

Microevolution & Macroevolution in Science Reference Books

If a scientist or science student wants to double-check the correct definition of a term, they aren't going to look at books like those above. Instead, they will look to a specialized reference book like those quoted here.

1. Microevolution describes the details of how populations of organisms change from generation to generation and how new species originate.

2. Macroevolution describes patterns of changes in groups of related species over broad periods of geologic time. The patterns determine phylogeny, the evolutionary relationships among species and groups of species.
Cliff's AP Biology 2nd ed, Phillip E. Pack, PhD

macroevolution: 1. genetic change sufficient to form new species. 2. evolution on a scale above the species level. 3. a large amount of change or a significant number of evolutionary steps, which may, however, consist of only minor alterations in allele frequencies, chromosome structure, or chromosome numbers, but with large phenotypic effects.

microevolution: 1. changes of allele frequencies in a population between generations. 2. a small amount of change or a limited number of evolutionary steps that consists of minor alterations in allele frequencies, chromosome structure, or chromosome numbers. 3. local evolution within populations and species.
The Cambridge Dictionary of Human Biology and Evolution, Larry L. Mai, Marcus Young Owl, M. Patricia Kersting

macroevolution Evolution that deals with large scale and complex changes such as the rise of species, mass extinctions, and evolutionary trends.

microevolution The smallest scale of evolution; changes within a species; a change in allele or genotype frequencies over time.
Encyclopedia of Biology, Don Rittner & Timothy L. McCabe, Ph.D.

macroevolution Macroevolution refers to the evolution of major new characteristics that make organisms recognizable as a new species, genus, family, or higher taxon (see speciation). Divergence of an evolutionary lineage into two or more lineages has also been called cladogenesis (“origin of branches”). In contrast, microevolution refers to small changes within an evolutionary lineage (also called anagenesis). Microevolution usually occurs by natural selection but can also occur as a result of other processes such as genetic drift.
Encyclopedia of Evolution, Stanley A. Rice, PhD