Evolution__3rd_Edition

522 PART 5 / Macroevolution
looked at in Chapter 18. Evo-devo is concerned with how developmental processes change
in evolution, and can cause changes in morphology.
In Chapter 21, we move on to the study of evolutionary rates. We see how they are
measured and consider one controversy a about the relative rates of evolution during, and
between, speciation events a in detail. Chapter 22 is about coevolution, in which the evolution
of one species is directed by evolutionary changes in the other species that make up its
environment.
The final chapter (Chapter 23) discusses the history of biological diversity a the number
of forms of life on Earth. Diversity can be measured by the number of species, and this is
controled by the relative rates of speciation and of extinction. One special topic is the
importance of mass extinctions. We look at such questions as whether mass extinctions
are real or artifactual, and whether they have shaped, or had little influence on, the history
of biological diversity.
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