8  •  Evolution and Natural Selection 315

Darwin’s dangerous idea

Evolution is an ongoing process 316

8.1

We can see evolution occurring right before our eyes. 316

Darwin journeyed to a new idea. 319

8.2

Before Darwin, many people believed that all species had been created separately and were unchanging. 319

8.3

A job on a ’round-the-world survey ship allowed Darwin to indulge his love of nature and make observations that enabled him to develop a theory of evolution. 321

8.4

Observing geographic similarities and differences among fossils and living plants and animals, Darwin developed a theory of evolution. 323

Four mechanisms can give rise to evolution. 325

8.5

Evolution occurs when the allele frequencies in a population change. 325

8.6

Mutation—a direct change in the DNA of an individual—is the ultimate source of all genetic variation. 326

8.7

Genetic drift is a random change in allele frequencies in a population. 328

8.8

Migration into or out of a population may change allele frequencies. 331

8.9

When three simple conditions are satisfied, evolution by natural selection is occurring. 332

8.10

A trait does not decrease in frequency simply because it is recessive. 335

Through natural selection, populations of organisms can become adapted to their environments. 338

8.11

Traits causing some individuals to have more offspring than others become more prevalent in the population. 338

8.12

Organisms in a population can become better matched to their environment through natural selection. 339

8.13

Natural selection does not lead to perfect organisms. 340

8.14

Artificial selection is a special case of natural selection. 341

8.15

Natural selection can change the traits in a population in several ways. 342

8.16

This is how we do it: By picking taller plants, do humans unconsciously drive the evolution of smaller plants? 344

8.17

Natural selection can cause the evolution of complex traits and behaviors. 346

The evidence for evolution is overwhelming. 348

8.18

The fossil record documents the process of natural selection. 348

8.19

Geographic patterns of species distributions reflect species’ evolutionary histories. 351

8.20

Comparative anatomy and embryology reveal common evolutionary origins. 352

8.21

Molecular biology reveals that common genetic sequences link all life forms. 355

8.22

Laboratory and field experiments enable us to watch evolution in progress. 356

StreetBIO: KNOWLEDGE YOU CAN USE

Evolution: what it is and what it is not . . . 358