Chp 17-Evolution of Populations -Explain how natural selection can impact allele frequencies of a population -Describe the factors that can contribute to the development of new species Endosymbiosis ● First organisms believed to be prokaryotes ○ What are characteristics of prokaryotes? ● Eukaryotes came about by symbiosis (living together) of single celled organisms ● What does natural selection directly act on, phenotype or genotype? ○ Phenotype-can only act on characteristics, not alleles ○ Indirectly affects genotype-affects what alleles are passed on to next generation ● Gene pool-all the genes/alleles that are present in a population ● Allele frequency-the number of times an allele occurs in a gene pool ● Evolution-change in allele frequency over time What alleles are in the gene pool? After a lava flow, what will happen to the allele frequencies of: Black fur? Brown fur? Genetic Recombination ● Genetic Recombination via sexual reproduction is source of variation ○ ex-think about you, your parents/siblings/relatives ○ don’t all look the same, due to mixing up of parents genes during meiosis (crossing over) Polygenic Traits ● Traits controlled by more than one gene ○ result in spectrum of phenotypes, rather than a few Directional Selection ● Individuals at one end of curve more fit than middle/opposite end ● What happens to the mean? Stabilizing Selection ● Individuals near middle of the curve more fit than those at the ends ● What happens to the mean? Disruptive Selection ● Individuals at outer ends have higher fitness than those near middle ● What happens to the mean? Examples: How do you think giraffes got their long necks? A. Directional Selection B. Stabilizing Selection C. Disruptive Selection Draw a graph to back up your answer. Genetic Drift ● RANDOM changes in allele frequency ● Is natural selection random? Bottleneck Effect ● Dramatic reduction in population size ○ disease, disaster etc ● Causes change in allele frequency Examples: cheetahs, elephant seals Founder Effect ● small group migrates away from rest of population, causes change in allele frequencies ○ ex: island populations Adaptive Radiation ● process in which organisms diversify rapidly into a multitude of new forms ○ change in the environment makes new resources available ○ opens environmental niches Genetic Equilibrium ● If no evolution is taking place, what happens to the allele frequencies? ● GE happens when pop not evolving, no change in allele frequencies Hardy-Weinberg Principle ● Used to predict allele frequencies in pops in GE ○ if allele frequencies don’t match, pop evolving ● allele frequencies stay the same UNLESS: ○ non random mating (sexual selection) ○ small pop (genetic drift) ○ immigration or emigration (individuals leaving/entering pop) ○ mutations ○ natural selection Species ● population or group of populations who can: ○ interbreed ○ FERTILE offspring ● speciation-forms new species Reproductive Isolation ● Species can’t breed anymore ● Splits gene pool Types of repro iso: ● Behavioral Isolation ○ diff courtship rituals ■ ex: birds with different songs Temporal Isolation reproduce at different times ex: flowers blooming at different times Types of repro iso: ● Geographic/habitat Isolation ○ geographic barriers separating pops ■ ex: canyons separating squirrel populations Types of repro iso: ● Gametic Isolation ○ produce gametes with different numbers of chromosomes ex: Horses have gametes with 32 chromosomes, donkeys have gametes with 31 chromosomes. Mules only have 63 chromosomes, and are unable to reproduce Gradualism: series of small changes over time (left) Punctuated equilibrium: sudden, dramatic changes followed by period of no change (right) Antibiotic Resistance ● Why is the Russian prison system considered to be "ground zero" in the fight against TB? ● What is responsible for the evolution of TB strains that are resistant to multiple drugs? ● How does the misuse of antibiotics affect the evolution of disease-causing bacteria? Use the theory of natural selection to explain the growing resistance to antibiotics. ● Why should we care about a resistant strain of TB in Russia? ● https://www.youtube.com/watch?v=W-WumllRPLI Read biology and society on pg 493 ● Why do doctors tell you to finish your antibiotics? Crash Course: 5 things he mentions you remember from yesterday 5 new things you learned Concept map Write Speciation in the middle of the paper. Create a concept map using the information your group wrote on their papers.
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