Evolution__3rd_Edition

xii Full Contents
10.5 Genetics of adaptation 266
10.5.1 Fisher proposed a model, and microscope analogy, to
explain why the genetic changes in adaptive evolution
will be small 266
10.5.2 An expanded theory is needed when an organism is not near
an adaptive peak 268
10.5.3 The genetics of adaptation is being studied experimentally 268
10.5.4 Conclusion: the genetics of adaptation 270
10.6 Three main methods are used to study adaptation 270
10.7 Adaptations in nature are not perfect 272
10.7.1 Adaptations may be imperfect because of time lags 272
10.7.2 Genetic constraints may cause imperfect adaptation 274
10.7.3 Developmental constraints may cause adaptive imperfection 275
10.7.4 Historic constraints may cause adaptive imperfection 281
10.7.5 An organism’s design may be a trade-off between different
adaptive needs 284
10.7.6 Conclusion: constraints on adaptation 284
10.8 How can we recognize adaptations? 286
10.8.1 The function of an organ should be distinguished from
the effects it may have 286
10.8.2 Adaptations can be defined by engineering design or
reproductive fitness 287
Summary Further reading Study and review questions
11. The Units of Selection 292
11.1 What entities benefit from the adaptations produced by selection? 293
11.2 Natural selection has produced adaptations that benefit various
levels of organization 294
11.2.1 Segregation distortion benefits one gene at the expense of
its allele 294
11.2.2 Selection may sometimes favor some cell lines relative to
other cell lines in the same body 295
11.2.3 Natural selection has produced many adaptations to
benefit organisms 296
11.2.4 Natural selection working on groups of close genetic
relatives is called kin selection 298
11.2.5 Whether group selection ever produces adaptations for the
benefit of groups has been controversial, though most
biologists now think it is only a weak force in evolution 301
11.2.6 Which level in the hierarchy of organization levels will
evolve adaptations is controlled by which level shows
heritability 305
11.3 Another sense of “unit of selection” is the entity whose frequency is
adjusted directly by natural selection 306
..