Macroevolution vs. microevolution is probably the primary issue debated between evolution and creationism, but is a minor issue in evolutionary theory itself. Few actual working scientists agree that there is much of a distinction between macroevolution and microevolution and most pay little attention to it, but creationists have seized upon it and try to magnify it into a major subject of debate. Creationists do this by misrepresenting what microevolution and macroevolution are.
Creationists misdefine the terms, misrepresent what scientists say about them, and pretend that there is some magical line separating them, preventing microevolution from becoming macroevolution. From a scientific perspective it shouldn't be necessary to spend a lot of time explaining microevolution and macroevolution, but creationist nonsense requires it. I have thus collected here, in almost excessive detail, how the terms are used by scientists.
When creationists use the terms microevolution and macroevolution, they don't mean the same thing as evolutionary biologists when they use the terms. Creationists use these terms to try to describe two fundamentally different processes. The essence of what constitutes microevolution is, for creationists, different from the essence of what constitutes macroevolution. Creationists act as if there is some magic line between microevolution and macroevolution, but no such line exists as far as science is concerned. Macroevolution is merely the result of a lot of microevolution over a long period of time.
Almost everything creationists say or write about evolution is, ultimately some sort of misrepresentation of science, but there is a special grouping of misrepresentations dealing with microevolution and macroevolution specifically. This is because questions about microevolution and macroevolution lie at the heart of creationist arguments against evolution today. Only the most foolhardy creationist denies the reality of microevolution, but they try to deny that this is "real" evolution. They insist that only macroevolution is real evolution and that there is some essential difference in how microevolution and microevolution occur.
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.
Scientists don't draw much of a distinction between macroevolution and microevolution because macroevolution is ultimately produced by microevolution — lots and lots of microevolution over long periods of time. Macroevolution is essentially microevolution. The basic mechanisms of macroevolution are also the basic mechanisms of microevolution. There is a difference, but it's primarily a difference of degree (the amount of evolution and the amount of time), not a difference of kind or essence.
The basic scientific perspective on macroevolution and microevolution is that macroevolution is lots of microevolution over time, but there are other natural processes that influence the course of macroevolution. This isn't much of a revelation because there are all sorts of natural processes that influence the course of microevolution as well. This doesn't change the fact that microevolution is fundamentally the operation of natural selection, mutation, genetic drift, and gene flow.
It is not possible to get an accurate picture of evolution from creationist literature — creationists simply won't use key scientific terminology the same way scientists do. Because the subject is scientific, though, this means they are using key terminology incorrectly. What's more, it's implausible that they are ignorant of the fact that they are using that terminology incorrectly. So, it's difficult not to conclude that they are simply lying about science for the sake of a religious agenda.
