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How Evolution Works • Where Does Variation Come From? • Mutations • Point mutation • Chromosomal mutation
How Evolution Works (cont’d) • How Natural Selection Works • Phenotypes in environments • Changes in gene frequencies • Directional Selection/ Stabilizing Selection
How Evolution Works (cont’d) • Other Ways By Which Evolution Happens • Gene Flow: movement of genes between populations • Genetic Drift: random changes in gene frequency in a population • Founder Effect: genetic bottleneck • Sexual Selection: Differential reproductive success within one sex of any species
Classification and Evolution • Taxonomy and Speciation • Systematics: branch of biology that describes organismal variation (what used to be called taxonomy) • Homology: the notion that similar features in two related organisms look alike because of a shared evolutionary history • Analogy: the notion that similar features in two unrelated organisms look alike because of adaptations to similar functions. (Convergent (parallel) evolution)
Classification and Evolution (cont’d) • Cladistics • Cladograms • Phenetics: numerical taxonomy What is a Species? • An interbreeding group of animals or plants that are reproductively isolated through anatomy, ecology, behavior, or geographic distribution from all other such groups (Mayr, 1942)
Classification and Evolution (cont’d) Species Concepts • Biological species concept • Evolutionary species concept • Ecological species concept • Recognition species concept
Classification and Evolution (cont’d) • Reproductive Isolating Mechanisms (RIMs) • Any factor that prevents a male and female of two different species from hybridizing • Premating RIMs • Postmating RIMs
Classification and Evolution (cont’d) • Premating RIMs • Habitat isolation • Temporal isolation • Behavioral isolation • Mechanical incompatibility • Postmating RIMs • Sperm-egg incompatibility • Zygote inviability • Embryonic or fetal inviability • Offspring inviability • Offspring sterility
Classification and Evolution (cont’d) • The Origin of Species: how species are formed • Anagenesis (whole group, no branching) • Cladogenesis (splitting events; branching) • Allopatric speciation (geographic isolation) • Parapatric speciation (separate habitats) • Sympatric speciation (form of anagenesis)
Classification and Evolution (cont’d) • The Tempo of Speciation • Gradualism • Darwinian • Gaps? • Macroevolution • Punctuated equilibrium
Classification and Evolution (cont’d) • Adaptation (Is everything adaptive?) Adaptations are evolved phenotypic traits that increase an organism’s reproductive success
Classification and Evolution (cont’d) Hardy-Weinberg Equilibrium (p + q)2 = p2 + 2pq + q2 = 1
Levels of Selection • Group selection • Inclusive Fitness • Behavioral ecology • Kin selection • Coefficient of relatedness rb > c • Hamilton’s Rule