If certain alleles are associated with a favored

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If certain alleles are associated with a favored phenotype (observable physical characteristics), they increase in frequency while other alleles decrease in frequency B.5 modes of natural selection 1.Directional selection changes the average value of a trait a)Tend to reduce genetic diversity in a population b)If this continues over time, favored alleles will eventually approach frequency of 1, while disadvantageous alleles reach a frequency of 0, alleles that reach 1 in frequency are said to be fixed, those that reach 0 are lost (purifying selection) c)Climate change d)2.Stabilizing selection reduces variation in a trait
Peyton Poppell 12
3.Disruptive selection increases variation in a trait
4.Balancing selection maintains variation in a trait
5.Sexual selection acts on traits that determine reproductive success
Peyton Poppell 13 A.A reduces or incompletely developed structure with no or reduced function but similar to functioning structures in closely related species B.They conflict with the thought that species are perfectly created and that species are static II.Lots of contemporary populations are changing in response to changes in their environment A.Bacteria have evolved antibiotic resistance B.Insects have evolved resistance to pesticides III.Data from fossil record and current species refute the notion that species are immutable- similar species are found in the same geographic areaA.Instead of being created independently, mockingbird populations that colonized different islands changed through time and became separate species IV.

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