MECHANISMS FOR EVOLUTION. Honors Biology. REVIEW. Evidence for Evolution and Examples What is Natural Selection? How did Darwin develop theory of Natural Selection?. PATTERNS OF EVOLUTION. Coevolution: 2 or more species evolve in association with one another
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
MECHANISMS FOR EVOLUTION Honors Biology
REVIEW • Evidence for Evolution and Examples • What is Natural Selection? • How did Darwin develop theory of Natural Selection?
PATTERNS OF EVOLUTION • Coevolution: • 2 or more species evolve in association with one another • Predators and Prey • Plants and Pollinators • Bats and Flowers
PATTERNS OF EVOLUTION • Convergent Evolution: • Organisms that look similar but are not related • Analogous features • Similar environments • Sharks and Dolphins
PATTERNS OF EVOLUTION • Divergent Evolution • 2 or more related populations or species become more and more dissimilar • Usually a response to new habitat • Can result in new species • Adaptive radiation • Artificial Breeding • Humans and Chimps
POPULATION GENETICS AND EVOLUTION • What did Darwin know? • Environment is important • Competition for Resources • Natural Selection: Individuals with traits more suitable for a particular environment are more likely to survive AND reproduce • What did Darwin not know? • Where does variation come from
POPULATION GENETICS • We now know that variation comes from genetics; no variation extinction • Population genetics: study of evolution from genetic point of view
WHAT CAUSES VARIATION • Need to think about variation in GENOTYPE • Mutation: change in DNA/chromosomes • Recombination: during meiosis • Random fusion of gametes
OTHER MECHANISMS FOR EVOLUTION • Things that upset genetic equilibrium • Using Hardy Weinberg you can predict genotypes; Only in hypothetical populations
MUTATION • Change in DNA or chromosomes • Make new alleles for a trait • Many are harmful • Can be neutral (code for same amino acid) • Some are beneficial
MIGRATION/GENE FLOW • Call it gene flow • Populations exchange genes • Increases within group variation • Decreases between group variation • DOESN’T HAVE TO BE MIGRATION
GENETIC DRIFT • Occurs in small populations • Allele frequencies shift as a result of RANDOM events • Coin Toss • Founders Effect; Bottleneck
NONRANDOM MATING • Sexual Selection • Positive assortative mating – mate with someone similar • Negative assortative mating: redheads!
NATURAL SELECTION • Darwin and neoDarwinians believe is the most important way evolution occurs • Types of Selection
STABILIZING SELECTION • Average form are selected for • Lizards: • Predators caught slow small and large visible • Select for medium size
DIRECTIONAL SELECTION • Individuals with an extreme trait are selected for • Anteaters with long tongues
DISRUPTIVE SELECTION • Individuals with either extreme are selected for • Limpet shell color; light and dark on different surfaces
SEXUAL SELECTION • Choosing mates based on traits • Intersexual Selection • Intrasexual Selection • Bird Color
SPECIATION • If enough changes accumulate new species • Biological concept of species: organisms can mate and produce fertile offspring; not just morphological (what they look like) • Isolating mechanisms speciation • Geographic isolation • Reproductive isolation
SPECIATION • Rates of speciation • Gradualism: species evolve gradually over time • Punctuated equilibrium: species go through times of fast change and slow or no change