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BIOL 1001
Tamara Kelly

B4 Phylogenetic Tree:represents evolutionary relationships with common ancestry branch population through time direction of branches is the direction of time node / fork a point in time when an ancestral species slip into descendant species tip / terminal node species that is living today or went extinct monophyletic group cut a branch, all attached is part of the group Microevolution: changing allele frequency D1 Evolution is a process that happens to populations. It doesn't happen to individuals because individuals are given a set of DNAthat does not change. DNAsequence can only change when offspring a born so evolution happens between generations. Many individuals that are born reproduce and die allow change in allele frequency to occur. D2 Variation is important for evolution so that the allele frequency can change. (if there is only one allele it will always remain and nothing will change). Variation is generated by mutation. (When looking at a graph/scenario: The more alleles, and the more evenly distributed those alleles are the more variation) D3 Hardy-Weinberg p^2 + 2pq + q^2 = 1 p^2 = genotype frequency of Homozygous q^2 = genotype frequency of Homozygous (adds up frequency of all 2pq = genotype frequency of Heterozygous genotypes) (phenotype frequency, if p is Dominant and q is recessive... p^2 + 2pq = Dominant phenotype frequency q^2 = recessive phenotype frequency p + q = 1 p = allele frequency q = allele frequency (adds up frequency of all alleles) Be careful if it says EGG or SPERM they only have one allele! so the chance of those having an allele is ‘p’or ‘q’. D4 Hardy-Weinberg acts as a null hypothesis for evolution because Hardy-Weinberg can ONLY happen if no mechanisms of evolution are occuring (mutation, sexual selection, genetic drift, gene flow, natural selection DO NOT occur in Hardy-Weinberg but are occuring in evolution) D5 Natural Selection: members of a species compete for resources and individuals with better adaptations have a better chance at reproduction. ● It does not move toward perfection but moves toward what survives best in the circumstances; in some situations an adaptation is useful but in other environments it is harmful. ● Natural selection is non-random because the worst adapted produce the fewest offspring. The genetic variation is random but the genetic variants that are useful will increase in frequency. ● Natural selection can only act on genes that cause a real life effect. If a unhelpful recessive allele is hidden by a helpful Dominant one the unhelpful allele will not be selected against. D6 Types of Natural Selection Stabilizing Selection / purifying Average is advantageous. The bell curve gets tall and narrow Directional Selection One extreme is advantageous. The bell curve moves left/right Disruptive Selection Average is disadvantageous / both extremes are advantageous. The bell curve splits into two D7 ● There are limits to adaptation because natural selection can only work on existing alleles. ● Also the ways in which the genes and traits are organised in the genome can cause limitations. For example when increasing the beak strength of a finch the beak width is also widened. It isnt possible to adapt to have both a narrow and strong beak. D8 Adaptation is not universally good because an adaptation in one environment or situation may be harmful in another situation. ● Fitness tradeoff example: Peacock males are coloured to attract females and also attract predators. D9 Mechanisms of Evolution Mutation ● adds more variation ● they appear randomly and are passed down vertically ● can be helpful or disappear because it stops Natural selection ● leads to adaptation ● reduces variation Genetic Drift ● random fluctuation in allele frequency ● more effect on small populations than large ones ● in conservation biology: a near extinction species has a small population, that population is more susceptible to a reduction in variation making it harder to recover ● can lead to allele fixation / disappearance ● reduces variation Gene flow ● migration ● makes populations more similar ● does not increase variation Nonrandom mating ● sexual selection (type of natural selection) ● reduces variation ● Founder effect and population bottleneck are both drastic reduction in population size. They make the population susceptible to genetic drift. Founder effect is when a small peice of a
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