Transcript Evolution
Evolution: Lamarck Evolution: Change over time Lamarck Use / disuse Theory of inheritance of ACQUIRED traits Evolution: Darwin Darwin’s Voyage on the HMS Beagle Evolution: Darwin / Natural Selection Darwin observed that organisms produce more offspring than the environment can support organisms VARY in many traits these variations can be inherited Some traits better fit for the environment than other traits Evolution: Darwin / Natural Selection Darwin = individuals best suited for a particular environment are more likely to survive AND reproduce than those less well adapted Darwin saw natural selection as basic mechanism of evolution As a result, proportion of individuals with favorable characteristics increases POPULATIONS (not individuals) gradually change in allele frequency in response to the environment Evolution: Natural Selection Evolution: Natural Selection vs Artificial Selection Artificial Selection - man creates pressure Four Evidence of Evolution Biogeography Fossils Comparative Anatomy Homologous Structures Comparative Embryology Molecular Biology DNA / Proteins / Amino Acid sequences Evidence for Evolution: Fossils Transitional Fossils Evidence for Evolution: Comparative Anatomy Homologous Structures: Similar structure (what does that suggest); different function (what does that suggest) Evidence For Evolution: Molecular Biology Convergent vs Divergent Evolution Analogous structure: similar function, different structure Ex. Wing of insect and bird Convergent Evolution Divergent Evolution Homologous Structures Microevolution vs Macroevolution Micro = small changes, still same species Macro = speciation Microevolution = change in allele frequencies in a gene pool Microevolution: Gene Pool Gene pool = total numbers of allele in a population Allele frequency = % of that specific allele in gene pool Hardy Weinberg Equilibrium Hardy-Weinberg equilibrium: even if alleles are shuffled in the next generation (new genotypes appear) allele frequency / proportions in the gene pool stay the same from generation to generation Hardy-Weinberg Equilibrium Large population Isolated population No genetic mutations Random Mating No Natural Selection Hardy-Weinberg Equilibrium ALLELE FREQUENCY p = “A” freq q = “a” freq p+q=1 GENOTYPE FREQUENCY p2 = “AA” freq 2pq = “Aa” freq q2 = “aa” freq p2 + 2pq + q2 = 1 Hardy-Weinberg: Genotype & Allele Frequencies Hardy-Weinberg: Genotype & Allele Frequencies Hardy-Weinberg Practice Problem In a certain population, the frequency of homozygous curly haired (HH) is 64%. What percentage of the population has curly hair? Given: p2 = .64 Find: p2 + 2pq p = .8 q = .2 2(.8)(.2) = .32 or 32% 64% (HH) + 32% (Hh) = 96% curly haired 5 Causes of Microevolution Population becomes SMALL due to chance: GENETIC DRIFT Population is NOT isolated: GENE FLOW Mutations occur Mating is NOT random Natural selection exists: some traits are better fit than others Causes of Microevolution: Genetic Drift: Gene pool changing due to CHANCE BOTTLENECK EFFECT Pop shrinks due to natural disaster FOUNDER EFFECT Colony leaves Gene Flow & Non Random Mating Gene Flow NONrandom Mating Causes of Microevolution: Natural Selection 3 outcomes of Natural Selection: Stabilizing, Directional, Disruptive/Diversifying Macroevolution: Speciation Speciation – the creation of new species Species: a population or group of populations whose members can interbreed and produce fertile offspring Reproductive Barriers Reproductive barriers prevents different species from mating with each other: Mating times / seasons different Different habitat Different mating behavior so little attraction between species Reproductive Barrier: Geographic Barrier Allopatric Speciation: When a population is cut off from its parent population, species evolution may occur gene pool is changed by natural selection, genetic drift, or mutation Geographic Barrier: Adaptive Radiation Adaptive radiation (ex of allopatric speciation) on an island chain – from one main species there are multiple different species evolving