Exam #2 Flashcards
proposed the Law of Succession: evolution explains the similarity between fossils of a location
-“on the law which has regulated the introduction of new species”
Alfred Russell Wallace
continental drift: noticed geological features on separated continents match when continents imagined together
-faced great opposition: could not explain how the continents moved apart
Alfred Wegener’s
plate tectonics, 1930s
Arthur Holmes
process by which the geographical range of a taxon is split into discontinuous parts by the formation of a physical barrier to gene flow
vicariance
“Population genetics is the most important, most fundamental body of theory in evolutionary biology”
Mark Ridley
genetic variation is the foundation of evolutionary change if it follows:
- mutations
- recombinant sex and horizontal gene transfer
- gene flow
example is spiral direction
discrete trait
example is skin color
continuous trait
variation comes in many forms:
- morphological
- cellular
- biochemical
- molecular
genetic effects
-inheritance, mutations
heritable
material effects
-composition of yolk, alcohol consumption
non heritable
changes that occur in individuals as a result of the environmental
environmental effects
not forward looking
not progressive
acts on existing traits
-occurs when there is a change in allele frequencies through time
nonrandom
assumptions underlying Hardy Weinberg equilibrium:
- organisms are diploid
- only sexual reproduction occurs
- generation are overlapping
- allele frequencies are equal in the sexes
-causes allele frequencies to change, often rapidly
-can lead to the loss of alleles except favored one
selection
-introduces new alleles into a population
-recurrent maintains alleles in the population, even if they are deleterious
mutation
-introduces new alleles into a population
-allele frequencies will become more homogeneous in the populations
migration
leads to random change in allele frequencies=genetic drift
small population size
-inbreeding increases homozygosity for all genes
-mate selection and directional selection can lead to the loss of alleles except favored one
non random mating
hardy weinberg equilibrium tells us what would happen without assortative mating, natural selection, migration, and mutation
null hypothesis
hardy weinberg equilibrium gives a mathematical demonstration that Medelian genetics preserves genetic variation
historical and conceptual importance
hardy weinberg equilibrium greatly simplifies our previously complex model for population genetics
theoretical importance
determines if the difference between the observed results and the excepted results in due to random chance alone
-does not prove/disprove if random chance is the only cause observed differences
chi squared test
assumptions of Hardy Weinberg equilibrium:
- no selection
- no mutation
- no migration
- large populations
- random mating
most important variable in the theory of evolution and it can be measured relative to selection
-it determines which genotype we can expect to see in the world today
fitness of genotypes
differential survival and reproduction of particular heritable genotypes over other
-can produce change rapidly in time even if it is a weak force
natural selection
chance of survival of a genotype
fitness (W)
measure of the relative fitness of a phenotype
selection coefficient (s)
selectively neutral compared to the dominant phenotype
s=0
complete lethality compared to the dominant phenotype
s=1
the fitness of a genotype increases as the genotype frequency in the population increases
-purifying selection
-gives an advantage to common alleles
–example: wing color in Heliconius butterflies
positive frequency dependent selection
the fitness of a genotype decreases as the genotype frequency in the population increases
-diversifying selection
-gives an advantage to rare alleles
–example: human influenza virus and plant self incompatibility alleles
negative frequency dependent selection
measure of genetic diversity
-high: increased diversity
-low: decreased diversity
–small populations are at a greater risk for this loss
heterozygosity
some evolutionary changes are predictable constancy from generation to generation
-example is natural selection
non random process
some evolutionary changes are not predictable constancy from generation to generation
-example if drift
random process
-fluctuations in the frequencies of alleles due to random chance alone
-most important in small populations
genetic drift
governed by or involving equal chances for each of the actual or hypothetical members of a population
random
not capable of being foretold; unknown in advance; irregular, not occurring at expected times
unpredictable
all the gene copies in the population can be traced back to a single ancestor
coalescence theory
merge or unite things; to merge or cause things to merge into a single body or group
coalesce
population undergoes a drastic reduction in size as a result of chance events
-lead to founder populations; have an affect on heterozygosity
bottleneck effect
small group of individuals (with a reduced genetic identity) creates a new generation
founder effect
true count
census
successful count
effective
effective size may be smaller than census size for many reasons:
- variations in population size (population bottleneck)
- variance in reproductive success (not all members are successfully mating)
- dioeciousness (selfing)
- skewed sex rations
- overlapping generations and age structured populations
matrilineal most recent common ancestor
-longest stretch of nonrecombining human mtDNA data
-most recent common woman from whom all living humans descend in an unbroken line of mothers
mitochondrial (MRCA)
patrilineal most recent common ancestor
-longest stretch of nonrecombining DNA in the human genome
-not as good at telling the story as the MRCA
y chromosome (PRCA)
bottleneck in human evolution
-one of the Earth’s largest eruption
-entire plant and worlds human population reduced
-evidence: human genetic studies, pollen studies from Bay of Bengal, stratified Toba ash
Toba Supereruption (YTT)
