Evolution__3rd_Edition

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Full Contents xi
8.9 Hitch-hiking occurs in two-locus selection models 210
8.10 Selective sweeps can provide evidence of selection in DNA sequences 210
8.11 Linkage disequilibrium can be advantageous, neutral, or
disadvantageous 212
8.12 Wright invented the influential concept of an adaptive topography 214
8.13 The shifting balance theory of evolution 216
Summary Further reading Study and review questions
9. Quantitative Genetics 222
9.1 Climatic changes have driven the evolution of beak size in one of
Darwin’s finches 223
9.2 Quantitative genetics is concerned with characters controlled by
large numbers of genes 226
9.3 Variation is first divided into genetic and environmental effects 228
9.4 Variance of a character is divided into genetic and environmental effects 231
9.5 Relatives have similar genotypes, producing the correlation between
relatives 234
9.6 Heritability is the proportion of phenotypic variance that is additive 235
9.7 A character’s heritability determines its response to artificial selection 236
9.8 Strength of selection has been estimated in many studies of natural
populations 240
9.9 Relations between genotype and phenotype may be non-linear,
producing remarkable responses to selection 242
9.10 Stabilizing selection reduces the genetic variability of a character 245
9.11 Characters in natural populations subject to stabilizing selection
show genetic variation 246
9.12 Levels of genetic variation in natural populations are imperfectly
understood 247
9.13 Conclusion 249
Summary Further reading Study and review questions
PART 3. ADAPTATION AND NATURAL SELECTION 253
10. Adaptive Explanation 255
10.1 Natural selection is the only known explanation for adaptation 256
10.2 Pluralism is appropriate in the study of evolution, not of adaptation 259
10.3 Natural selection can in principle explain all known adaptations 259
10.4 New adaptations evolve in continuous stages from pre-existing
adaptations, but the continuity takes various forms 263
10.4.1 In Darwin’s theory, no special process produces
evolutionary novelties 263
10.4.2 The function of an adaptation may change with little
change in its form 264
10.4.3 A new adaptation may evolve by combining unrelated parts 265