exam 3 keiser Flashcards
what is evolution
change in the genetic compostiion of populations over time/alelle frequencies across generation
Evolutionary theory
how and why evolution occurs
Evolutionary theory
how and why evolution occurs
foundations of evolutions
variation, natural selection, heritability, genetic drift, common ancestors
variation
genotypes influence different phenotypes
heritability
phenotypes are passed down from parents to offspring via genes
heritability
phenotypes are passed down from parents to offspring via genes
genetic drift
more variation can arise through mutations
decesent with modifcation
charles darwin and lyell’s theory about evolution
endemic species
exist in only one location
alfred wallace
co founder of evolution, mostly known for biogeography
evolutionary synthesis
happened afte rhte discovery of mendelian genetics, reconciled evolution and genetics (1950s)
fitness
: the sucess of a pheontype regarding survival and reproductive capability RELATIVE TO OTHER PHENOTYPES
adaption
beneficial trait that spreads through a population by natural selection (also the process that produces it)
what generates variation
mutation and migration
what reduces variation (sometimes)
selection and nonrandom mating
mutations
changes in nucleotide sequences taht occur in individuals
genetic drift
small changes in allele freuence that produce large changes over time
when is genetic drift most effect
in small popualtions, with neutral mutations over time
allele frequency
the proportion of each allele in the “gene pool”
what does at allele frequence of 1.0 / 0.5/ 0 mean?
1.0 - everyone has this allele (fixation)
0.5 = half of the population has this allele
0 = no one has this allele
population bottlenecks
caused by extreme declines in populaiton size, reducing genetic variation in the survivng population (elephant seals)
founder effects
initiation of a new population with fewer individuals, reducing variation in the survivng population
migration
movemnet of alleles from one population to another, increased variations (gene flow)
selection
reduces variation sometimes (natural selection reduces individuals with deleterious allelles
what is selection usually represented by
frequency distributions
frequency distributiosn
vizualize count data, can show absolute frequences or relative frequences, like proportions or percentages
sexual selection
when individuals choose partners based on thier charactersitics (can lead to things like long tails, colorations)
modes of selection
directional, disruptive, stablizing
direction selection
more colorful moths are eat by birds, grey moths survive and reproduce
stabilizing selection
when individuals closest to the mean have the highest fitness, reduces variation but doesnt change the man (purifying selection)
disruptive selection
increaes variation can generate polymorphisms
polymorphisms
stable, discrete categories of pheotypes - smaller beaked birds have an advantage (can eat small seeds) big beaked birds have an advantage (can crack big seeds), medium beaked birds have it rough
heterozygote advantage
in changing condiitons, heterozygous indivs outperform homozygotes, which helps maintain allele variety.
Geographic variation
genetic variation is maintained in populatiosn in different geographic regions with different selective pressures
Frequence dependent selection
maintains genetic variations - polymorphisms can be maintained when its fitness is determined by its frequencey (scale eating fish, the rarer type will always have less competitions)
artifical selection
purposefully guided by humans with a goal in mind
agricultural research
long term selection experiemnts showed that selection can result in strong phenotypic differences and that trait change can be reversed
what does artificial selection need to function
existing genetic variation
heritability
estimates the proportion of variation in a trait determined by inherited genes and the enviornment
what does it mean if H^2 = 1
All variation in a population is due to genetic differences
what does it mean if H^2 = 0
no genetic varioan; all variaiton in the population comes from differences in the enviornments experiences by the individuals
equation for hertiability
variation inherited / (vinherited + venviornment)
what is heritability not
its is not genetic determination
factors that affect heritability
precision of measurement, enviornmental change, migration/gene flow, inbreeding
the higher the heritability estimate -
the easier it may be to modify that trait via artificial selection
The breeders equation
a foundation toool in quantitiative genetis, used to prdict evolutionary change - R = h^2S (h^2 = heritability, s = selection differential, R = response to selection)
what does the breeder’s equation assume
the trait of interest is not correlated with other traits affecting fitness
population genetic structures
can be described by frequences (0-1) of alleles and genotypes
formula of allele frequency
p = 2NAA + NAa = 2N (same with aa for the recessive)
p+q
ALWAYS 1
fixed
p = 1, q = 0 (or vice versa)
Hardy-Weinberg equilibrium
conditions for populaiton allele frequencies to stay the same
what are the 5 conditions for hardy weinberg equilibrium
no mutation, no selection, no gene flow, population size is infinite, and mating is random
how quickly can you restore HW equilibrium
one generation
what do deviations from HWE show?
that evolution is occuring
trade-offs in sexual selection
more likely to reproduce, but less likely to survive
2 main forms of sexual selection
intrasexual competition, mate choice
good genes hypothesis
some traits are honest signals of mate quality
runaway sexual selection
offspring will inherit their parent’s ornamental traits and preferences for that trait
genetic (sexual) conflict
when genes that govern males and female traits are anatgonistic
mutations
novel gene combos
nucleotide substitutions
changes in one nucleotide in a DNA sequence
synonymous substitutions
do not affect the function of a protein - neutral
nonsynonymous substitution
affect protein function, can ve deleterious, neutral or advantageous
hybrid incompability
offspring ofspring of individuals from different populations or even species are worse off
where are rates of substitution higher?
at synonymous sites vs non synonymous sits
neutral theory of molecular evolution
majority of evolutionary changes occursa t the molecular level and most genetic variation is due to random genetic drift of alleles that are selectively neutral
although genetic drift of exist gene variants is stronger in small populations
the rate of fixation of new neutral mutations is independent of population size
molecular clock
the rae of fixation of new neutral mutions is relatively constant, so it can be used as a molecular clock to calculate evolutionary diverengce times between species
dn
of nonsynonymous substitutiosn per non synonymous site
ds
numbers of synonymous substitutions per synonymous site
dn/ds = 1
neutral
dn/ds > 1
positive directional selection
dn/ds < 1
stabilizing selection
gene expression
might account for mucch of the evolution of diverse body forms we observe across living organisms
homeotic mutations
replaces one structure with another
genetic switches
can turn genes on or off, regulate gene expression
heterometry
different amount of gene expression
heterochrony
different timing of gene expression
heterotropy
spatial diference in difference in gene expression
phylogeny
evolutionary history of genetic relationships
phylogenetic tree
visual reconstruction of shared history
lineage
series of ancestor and descendant populations
components of a phylogenetic tree
vertical distances between branches have no meaning, order after a node is arbitrary
nodes
indicate timing of splitting events
split events
a speciation event, gene dupliction, transmission event etc
homologous features
shared by two or more species and inherited fro m a common ancestor
ingroup
the group of organisms of primary interest
outgroup
species closely related to by phylogenetically outside of the group of interst
parsimony
the preferred explanation of observed data is the simplest explanation
convergent evolution
different selective pressures on different taxa led to similar traits
Taxa
expected to be monophyletic - can be cut off from a phlyogenetic tree witha s ingle cut in the tree
polyphyletic groups
do not include its common ancestory - birds and mammals are warm blooded, but it doesnt inlcude their common ancestors
paraphyletic
do no include all the decsendants of a common group - reptiles inlcudes turtles, snakes etc, ut not birds even through they are within that lineage
how is a molecular clock calibrated
the fossil record, known times of divergence, biogeographic data
species
groups of organisms that share genetic and morphological attributes, and are reproductively isolate from other such
speciation
Divergence of biological lineages and emergence of reproductive isolation
what did linneaus base the taxonomic system off
appearance / morphological concept
polymorphisms
multipe phenotypes within one species
cryptic species
two or more species that are indistinguisable
biological species concept
species are groups of actually or potentially interbreeding natural poplaitons that re reproductively isolaed from other such groups
reproductive isolation
two groups can not make viable offspring
complications with biological species conept
asexual reproduction, extinct groups only known from fossils, hybridization between closely related species
phylogenetic / lineage species concept
a species is a branch on a phylogeny which ahs a history that starts at a species event and ends at another speciation or extinction
Dobzhansky Muller model
genetic basis for disruptiv selection which leads to speciation
hybrid incompatibility
two species interbreed but their offspring are bad at surviving so they eventually stop breeding wth each other
hybrid zones
when reproductive isolation is incomplete
what maintains species barriers
hybrid suffering
do hybrid zones always reinforce species barriers
no, sometimes they can relax barrier and act as a bridge between species
allopatric speciation
speciation that results when a pop is divided by a physical barrier
sympatric speciaiton
no physical isolation, occurs within the same population
sister species
species that are each others closeset relatives can arise on opposite sides of the barrier
ecological speciation
divergent natural selection ebtween contransting ecological enviornemnt
ecological speciation
divergent natural selection ebtween contransting ecological enviornments
polyploidy
the duplication of sets of chromosomes within indivs, can result in complete reproductive idolation in 2 generations
temporal isolation
changes in breeding season can cause reproductive isolation
behavioral isolation
mating and stuff are different
adaptive radiation
rapid diversification of a large number of descendant species from a single ancestor species that now inhabit a variety of enviornments
who has high speciation rates
groups with poor dispersal abilites, and lineages with strong sexual selection
stratigraphy
the study of geological strata - the oldest rocks on the bottom strata and the new rocks on top
radioisotopes
decay in a predictable pattern over long period of time
half-life
half of the atoms in a radioisotope decay to become a different, stable (nonradioactive) isotope
radiometric dating
the use of radiosotopes to date fossils and rocks is known as radiometric dating
paleontology
extinct life
3 time periods to know
archean cambrian creataceous
continental drift
the movement of continents due to plate tectonics
plate tectonics
geophysical movements of the “plates that make up the Earth’s layer
pangea
big ass continenet
mass extintictions
things like meteors, sea level
atmospheric changes
atmosphere did not have much oxygen until cyanobacteria came on the scene
more oxygen
big ass bugs
permineralization
occurs when an organism is buried in sediment and empty spaces are filled with minerals
holotype
a single physical speciment used to describe a species
casts and molds
the organisms dissolves and leaves an organism shaped hole
impressions
trace fossil that hint at an extinct organisms biological activity but don’t contain any organic material
abiogenisis
origin of life, RNA first hypothesis
Miller - Urey Experiment
tested the chemical origin of life hypothesis and produced ovr 20 amino acids from chemicals and electricity
cambrian explosion
glaciers recede, increasing o2, and huge explosion of biological diversity
mass extinctions
end of ordovician -> glaciers formed and oceans receded and 75% of things died
permian
pangea, and at th end there were massive volcanic eruptions that cooled the climate and then created a glaciation event - 96% of all multicellular species became extinct at the end of the permian
KT extinction
at the end of the cretaceous period, meteor struck in mexico and killed alll non - avian dinosuars plant life died too
hominin evolution
bipedal locomotion, split off from chimpanezees
