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phylogeny = evolutionary history of a species or group of related species

systematics =

binomial nomenclature

  • system of taxonomy based on resemblances

  • two part names for species and hierarchical classification

    • two part scientific name of a species = binomial

      • first part: genus

      • second part: specific epithet (unique for each species within the genus)

  • hierarchical classification

    • grouping species in increasingly inclusive categories

linking classification and phylogeny

  • carnivora (order)

    • 3 families, 4 genus, and 5 species

  • what to take away from phylogenetic trees

    • these represent a hypothesis about evolutionary relationships

  • rooted tree

    • includes a branch to represent the most recent common ancestor of all taxa in the tree

cladistics

  • grouped by common ancestry

  • monophyletic groups = consist of ancestor and its descendants

  • paraphyletic group

  • polyphletic group

average heterozygosity = measures gene variability, the average % of gene loci that are heterozygous

nucleotide variability = measures the mean level of difference in nucleotide sequences among individuals in a population.

formation of new alleles

altering gene number or position

  • large chromosomal mutations that delete, disrupt or rearrange many loci are usually harmful

  • if duplicated, mutations can accumulate and new functions may arise

  • occurs due to errors in meiosis

  • increases in gene number likely played a major role in evolution

sexual reproduction

  • most genetic variation in sexually reproducing organisms results from recobination

  • new combinations of existing alleles occur through three mechanisms

    • crossing over

    • independent assortment

    • fertilization

gene pools and allele frequencies

  • a population is a group of individuals of the same species that live in the same area and interbreed

  • geographically isolated populations rarely exchange genetic material

  • if populations are not isolated, individuals still usually only breed with members of their own population

  • gene pool = all copies of every allele at every locus in all members of the population

  • a locus is fixed if all individuals in a population are homozygous for the same allele

  • two or more alleles for a locus - individuals may be homozygous or heterozygous

  • calculating frequency

    • p = frequency of C^r = 800/(800+200) = 0.8 (80%)

    • q =1 = p = 0.2 (20%)

hardy-weinberg equation

  • describes the expected genetic makeup for a population that is not evolving at a particular locus

  • if the observed genetic makeup of the population differs from expectations under hardy weinberg, then the population may be evolving

natural selection

  • based on differential success in survival and production

  • selection results in alleles being passed to the next generation in proportions that differ from those in the present generation

  • can cause adaptive evolution (traits that enhance survival or reproduction increase in frequency over time)

genetic drift

  • process in which chance events cause allele frequencies to fluctuate unpredictably from on gen to the next

  • reduces genetic variation due to random loss of alleles

  • ex:

Directional selection = favors individuals at one extreme end of the phenotypic range

Disruptive selection = favors individuals at both extremes of the phenotypic range

Stabilizing selection = favors intermediate variants and

acts against extreme phenotypes

sexual selection = process in which individuals with certain heritable traits are more likely to obtain mates than other individuals of the same sex

sexual dimorphism = difference in secondary sexual characteristics between the sexes

intersexual selection = direct competition among individuals of one sex (often males) for mates of the opposite sex

  • occurs when individuals of one sex (usually females) are choosy in selecting their males