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Lamarck = Inheritance of acquired characteristics Giraffe stretches neck over several generations to reach leaves high in trees Lamarck Natural selection – favorable new traits resulting from random mutations are passed on to succeeding generations Darwin Darwin = Proposes the “Origin of Species” (by natural selection) 5 year world cruise Ancestral bird “adapts” (by natural selection) into various habitats leaves seeds fruit Vegetarian insects insects Ancestor? grubs Uses tools seeds Woodpecker cactus Darwin’s Finches Microevolution: Change in the gene frequency within a population Provides new genetic material for new traits …… without which all life would look the same ….. like the first life. Many bacteria, including resistant variety Expose all bacteria to antibiotics; most normal die Resistant bacteria multiply and dominate Entire infection evolves into resistant strain % RESISTANCE Add Antibiotic Normal bacteria Resistant bacteria Dead bacteria Example of microevolution Causes of microevolution: 1. Mutation – nucleotide or chromosome 2. Non random mating – mate selection 3. Gene Flow - migration 4. Genetic Drift – accidental loss of individuals 5. Natural Selection – most fit reproduce more often UV light Thymine dimer Radiation (x-ray) causes chromosome damage With and without mutation No mutation mutation No mutation mutation No mutation No mutation Factors that will cause microevolution: 1. Mutation – nucleotide or chromosome change 2. Non random mating – mate selection 3. Gene Flow - migration 4. Genetic Drift – accidental loss of individuals 5. Natural Selection – most fit reproduce more often Non random mating The wolf is probably close to natural dog if dogs allowed to mate freely Specific breeds of dog result if dogs are only allowed to breed with others in the same breed 20,000 Cheetahs Extreme example of nonrandom mating = inbreeding Results in mostly homozygous genotypes (e.g. HH or hh) Cubs low survival rate Susceptible to disease Males have low sperm count Only chance for new genes is through mutation Factors that will cause microevolution: 1. Mutation – nucleotide or chromosome change 2. Non random mating – mate selection 3. Gene Flow - migration 4. Genetic Drift – accidental loss of individuals 5. Natural Selection – most fit reproduce more often Gene flow (migration) Genes for the brown beetle move to green population Population A = 100% green Population B = 100% brown Factors that will cause microevolution: 1. Mutation – nucleotide or chromosome change 2. Non random mating – mate selection 3. Gene Flow - migration 4. Genetic Drift – accidental loss of individuals 5. Natural Selection – most fit reproduce more often Genetic Drift: accidental loss of members of a small population 33% purple 20% purple 33% purple 32% purple Small population with 12.5% white and 87.5% dark 75% dark 25% white 100% dark 0% white Factors that will cause microevolution: 1. Mutation – nucleotide or chromosome change 2. Non random mating – mate selection 3. Gene Flow - migration 4. Genetic Drift – accidental loss of individuals 5. Natural Selection – most fit reproduce more often Light moth reproduces more often – why? Bird eats dark moth Dark moth reproduces more often – why? Bird eats light moth Best adapted moth reproduces more offspring Natural Selection does not give an organism an adaptation simply because it will do better with it. – Adaptations occur by chance mutations Factors that will cause microevolution: 1. Mutation – nucleotide or chromosome change 2. Non random mating – mate selection 3. Gene Flow - migration Review 4. Genetic Drift – accidental loss of individuals 5. Natural Selection – most fit reproduce more often SPECIES = group of interbreeding populations reproductively isolated from other populations Are lions and tigers separate species? Liger = lion x tiger Are horse and donkey different species?? Horse X sperm Donkey egg = Mule (sterile) No meiosis Ensatina eschscholtzii Geographic Isolation can lead to differences and new species Becomes separate species as mutations make them different Ensatina eschscholtzii Kaibab and Abert’s squirrels separated by Grand Canyon = geographic isolation Colorado River Geographic isolating mechanisms (fences) prevent exchange of genetic differences between dog breeds allowing differences to build-up If population is geographically isolated long enough, then behavioral isolating mechanisms occur