evolution and pop gen Flashcards
what is genetic drift
the change in allele frequencies in a population due to random chance
this will typically occur due to nat disaster or accidents
what might happen if genetic drift occurs on a smaller pop
potential risk of losing entire alleles
what is a fixed allele
when there is only 1 type of allele present or left in a population
what is a population bottle neck
a temporary/ larger reduction of individuals due to a nut disaster, disease or human influence. this results in a loss of overall genetic diversity
what is the founder effect
when a small sub population colonizes a new location. usually the allele frequency will differ in this area when comped to the source/ parent population
what is gene flow
the continuous introduction or removal of alleles between populations vai the movement of individuals
what is reproductive isolation
the lack of gene flow between populations. when this occurs species may result.
what are the 3 broad ways to define a species ( concepts)
morphological, phylogenic and biological
what is the morphological species concept, and what does this entail
classification of orgs based on conserved (similar) anatomical features
what is the phylogenetic species concept
classification/ defining organs based on their evolutionary history and phylogenetic similarity
what is the biological species concept
the classification of orgs by their ability to interbreed ad produce viable,fertile offspring
what is reproductive isolation. what are the different types
barriers which prevent 2 orgs to breed successfully this maybe be geographical, behavioral, physiological or genetic
there is prezygotic and postzygotic mechanisms
prezygotic mechanisms
ecological iso: 2 orgs are physically spe and cannot come together
temporal iso: different fertility times
behavioural iso: the behavioral cue or one or both indiv are not met
mechanical iso: reproductive parts (genitalia) do not fit and cannot deliver the pollinators
post zygotic mechanisms
hybrid inviability: abnormal zygotic development to which the offspring will die before repord maturity
hybrid sterility: normal development of the hybrid but is unable to produce viable gametes
what causes speciation
reproductive isolation. this occurs of the shift occurs in a reproductive trait commonly by genetic drift or natural selection
what are the three forms of speciation wrt geography
allopatric
parapatric
sympatric
allopatric speciation
a group is divided by a geographical barrier
parapatric speciation
when a population expands into a new habitat and will generally occupy new nieches. the parent population still remains and gene flow may occur
what is sympatric speciation
when a parent pop form genetically distinct sub populations by natural selection. this occurs without isolation.
what is ecological speciation?
the formation of barries to gene flow between pop based on ecologically divergent selections orgs have between environments. this means as the environment differs from the og environ, there is a greater chance for report isolation to occur
set of org are adapted to a particular niche, posing as the isolating barrier between populations
what is assortative mating
the tendency for indiv to choose mates. this may be positive (similar) or negative (different)
how does sympatric speciation typically occur
when a disruptive selection for a specific trait emerges and. is coupled with assorting mating. commonly it is the positive assortative mating that results in sympatric
complete dominance
in a hetero, one allele is expressed (dom) while the other is repressed (recessive)
incomplete dom
the 2 allele work to express an intermediate pheno type
white+ red= pink
co-dominace
when both allele are dominant in a heterozygote. both are expressed (pattern showing both)
what are the assumptions of HWE
no natural selection
random mating
no genetic drift due to a large population
no migration (gene flow)
no mutation
any violation to these will lead to evolution
what is the HW principle
the idea that the allele frequencies will remain stable from one generation to the next. if this is true then the population is in equilibrium and evolution IS NOT OCCURING
what are the prezygotic isolating mechanisms
ecological (finding mate)
temporal (fertile)
behavioral (cues)
mechanical (mating/ zygote formation)
what are postzygotic isolating mechanism
hybrid inviability (zygote/ embryonic development)
hybrid sterility (no further continuation of sepices)
