Evolution Flashcards
(37 cards)
What is natural selection?
best adapted organisms survive and pass on their traits to their offspring
What are Darwins assumptions
- individuals within species are variable
- some variations are passed onto offspring
- in most generations, more offspring are produced that can survive
- survival and reproduction are not random - survival of fittest
What is evolution?
survival of the fittest
occurs because of changes in allele frequencies
fittest genotypes vary between populations
divergence of populations leads to speciation
what is the modern synthesis of evolution?
considered in terms of changes in allele and gene frequencies over time, and the average action of selection on genotypes
when does selection act on alleles?
in relation to their average contribution to their action on the individuals that carry them
acts on levels of individuals
transmission of alleles important
When does selection operate?
to remove less fit variants, or increase variants with greater fitness
artificial selection
- humans affected genotypes of dogs & can remove and select for different phenotypes
what is invasion of rare mutants?
new alleles are constantly created
dominant allele are always expressed, selection against will remove excess alleles
What is genetic drift?
chance difference in transmission of alleles, leading to fluctuations in allele frequency
greater influence than selection
increases rare recessive alleles
What is a genetic bottleneck?
random allele is lost
founder effect
significant as reduction of population
completely random and small surviving population
what is balancing selection?
how variation is maintained in a population
selection both for and against
what is frequency dependent selection?
Rare alleles producing unusual phenotypes may be predated on less than those with the main allele
Alleles can become common and predators learn their patterns
what is fluctuating selection?
also select for rare alleles
unstable and changeable
may favour opposing phenotypes over short timescales
what is fitness?
Used to measure reproductive success, described as the ability to both survive and reproduce and is equal to average contribution of the gene pool of the next generation that is made by an average individual of the specified genotype of phenotype.
what ate the methods for measuring fitness?
- relative survival of genotypes within a generation
- changes in gene frequencies between generations
deviations from hardy-weinburg ratios
what is fitness equation?
W = 1 -s
w is fitness
s is selection
selection determines how fast allele frequencies change
when s is high, allele frequencies change rapidly
selection example
peppered moths
mark release recapture experiments and found dark forms adapted to survive in industrial revolution
mark release recapture technique
tested how well survived in different environments
recapture allows to see survival rate
assume optimal survivorship
ca then calculate selection coeffecient
what is an adaptive landscape?
natural selection tends to move populations towards peaks of hills
never ending evolutionary journey
visualise relationship between genotypes and phenotypes
what is stabilising selection?
stabilises a population
intermediate variants are selected for
most common
what is directional selection?
individuals at one extreme are selected for
shift
what is disruptive selection?
individuals at both extremes are selected for
bimodal distribution
what is sexual selection?
competition for mates
maximises reproductive success
even at potential cost to survival
extreme case of natural selection
what does kin selection refer to?
changes in gene frequency across generation driven by interactions between related individuals
Natural selection of genes that tend to cause the individuals bearing them to be altruistic to close relatives
helping your relatives, even at a cost to yourself, you may be promoting the success and transmission of genes that you share in common
