microevolution Flashcards
what is microevolution
change in allele frequency in population/species across generations
–> evolutionary change over shorter time periods
what is macroevolution
evolution above species level –> variation among species and questions related to diversification
–> over long periods of time
(T/F) macroevolution is the results of microevolution
T
what are the 4 processes that can cause microevolution
- mutation
- gene flow
- genetic drift
- natural selection
what does microevolution NEED
genetic variation
what is panmixia
random mating in a population
what is random mating
individuals mate randomly with respect to their genotype at locus of interest
what is non-random mating
mating system in which at least some individuals are more or less likely to mate with individuals of a particular genotype than with individuals of other genotypes
–> more common
why is mating often non-random
- relatives may mate more often or less often than expected by chance
- individuals may self-fertilize more or less often than expected by chance
- individuals may mate more often with others more or less similar to them in phenotype than expected by chance
what is inbreeding
when mating takes place between related individuals
–> resulting offspring are inbred
what are the effects of inbreeding
can cause increase in frequency of homozygotes
–> 1+ generations of random mating may restore HW ratios
what is inbreeding depression
decrease in fitness as a consequence of inbreeding
–> can increase loss of gene variation that occur in small populations due to genetic drift
what are the 2 mendelian causes of inbreeding depression
- dominance hypothesis: alleles that decrease fitness (deleterious alleles) tend to be partially-completely recessive –> homozygosity will increase expression of these alleles
- heterozygote advantage: heterozygotes have higher fitness than either homozygotes –> increased homozygosity = lower fitness
what is outbreeding
mating between individuals that are less related
what are the effects of outbreeding
increases heterozygosity
what is heterosis
increase in fitness relative to non-outbred individuals
how does heterosis occur
- deleterious alleles more likely to be masked
- heterozygotes have higher fitness
what is a mutation
a change in genetic information of an organisms DNA
what are the effects of mutation
can create new alleles –> ultimate source of genetic variation
–> RANDOM
when are mutations heritable
if they are present in the germ line
what are the types of mutation
small scale (point mutation):
- substitution: single nucleotide is replace with another –> silent or replacement
- insertion/deletion: 1+ nucleotide is added or removed
large scale: mutations in chromosomal structure
- translocation
- inversion
- duplication
(T/F) most new mutations are beneficial
F
what is gene flow (AKA migration)
movement of alleles between populations occuring via migration
–> introduces/removes alleles from populations
what are the effects of gene flow
homogenizes populations –> reduced genetic variation
what is local adaptation
population adapts to its local environment
can gene flow impede local adaption
yes, by constantly introducing maladaptive alleles from other populations –> outbreeding depression
what is genetic drift
random changes in allele frequencies across generations
–> occurs due to sampling variation: difference between value in finite sample compared to true population size
effects of genetic drift
causes unpredictable changes in allele frequencies
typically reduces genetic variation –> alleles are lost
will cause populations to diverge from one other (without gene flow)
what are population bottlenecks
severe decrease in population size which reduces genetic variation and enhances genetic drift
what is a founder effect
small group of individuals colonize a new geographic area, isolated from other populations
what does natural selection act on
phenotypes
what is frequency-dependent selection
when fitness of a phenotype depends on its frequency in the population
what is positive frequency-dependence
directional selection for a phenotype strengthens as phenotype becomes more common
what is negative frequency-dependence
directional selection for phenotype is stronger when the phenotype is less common
–> form of balancing selection
what is heterozygot advantage
when heterozygote at locus has a higher fitness than either homozygotes
