Part
Five -The Patterns and Processes of Evolution 463
22.
The Mechanisms of Evolution 486
22.1
What Facts Form the Base of Our Understanding
of Evolution? 487
Adaptation has two meanings 489
Population genetics provides an underpinning
for Darwin’s theory 489
Most populations are genetically variable
490
Evolutionary change can be measured
by allele and genotype frequencies
491
The genetic structure of a population
does not change over time if certain
conditions exist 492
Deviations from Hardy–Weinberg
equilibrium show that evolution is
occurring 493
22.2
What Are the Mechanisms of Evolutionary
Change? 494
Mutations generate genetic variation
494
Gene flow may change allele frequencies
494
Genetic drift may cause large changes
in small populations 494
Nonrandom mating changes genotype
frequencies 495 22.3
What Evolutionary Mechanisms Result
in Adaptation? 497
Natural selection produces variable
results 497
Sexual selection influences reproductive
success 498
22.4 How Is Genetic Variation Maintained
within Populations? 501
Neutral mutations may accumulate within
populations 501
Sexual recombination amplifies the
number of possible genotypes 501
Frequency-dependent selection maintains
genetic variation within populations
501
Environmental variation favors genetic
variation 502
Much genetic variation is maintained
in geographically distinct subpopulations
503
22.5 What Are the Constraints on Evolution?
503
Developmental processes constrain
evolution 504
Trade-offs constrain evolution 504
Short-term and long-term evolutionary
outcomes sometimes differ 504
