Evolution Any change in the genetic constitution of a population of organisms Changes of lesser magnitude are called microevolution Changes at or near the upper extreme are called macroevolution Table 12 1 Microevolutionary Processes Mutation A heritable change in DNA Natural selection Change or stabilization of allele frequencies an outcome of differences in survival and reproduction among variant individuals of a population Genetic drift Random fluctuation in allele frequencies over time due to chance occurrences alone Gene flow Individuals and their alleles move into and out of populations the physical flow counters the effects of the other microevolutionary processes Table 12 1 Page 194 phenotypes of original population A seabird carries a few seeds stuck to its feathers from the mainland to a remote oceanic island phenotype of island population Development of a Theory Lyell Gradualism Geological changes occur over millions of years Lamarck Acquired characteristics are inherited Darwin and Wallace Natural Selection Natural Selection Four Mechanisms of Natural Selection More born than can survive Not everyone makes it Variability in the population Genetic differences Heritability of traits The differences are inherited Fitness Some produce more offspring than others Geospiza conirostris G scandens Do not post to Internet Certhidea olivacae Camarhynchys pallidus Starting population Next generation Next generation 490 AA butterflies dark blue wings 490 AA butterflies dark blue wings 490 AA butterflies dark blue wings 420 Aa butterflies medium blue wings 420 Aa butterflies medium blue wings 420 Aa butterflies medium blue wings 90 aa butterflies white wings 90 aa butterflies white wings 90 aa butterflies white wings Number of individuals Directional selection Number of individuals Range of values at time 1 Number of individuals Range of values at time 2 Range of values at time 3 Number of individuals Number of individuals Range of values at time 1 Range of values at time 2 Number of individuals Stabilizing Selection Range of values at time 3 Number of individuals Disruptive Selection Number of individuals Range of values at time 1 Number of individuals Range of values at time 2 Range of values at time 3 100 20 50 15 30 20 10 10 5 5 3 2 1 2 3 4 5 6 7 8 9 birth weight pounds 10 11 percent mortality percent of population 70 Figure 12 15 Page 190 Do not post to Internet