Evolution Flashcards
what is the gene pool ?
range of alleles present in a population
what is the term for how often an allele occurs in a population ?
allele frequency
state what evolution is
change in allele frequency over time
what is selection pressure ?
factor (predatation/disease/competition) that creates a struggle for survival
what is stabilising selection ?
- environment is constant
- individuals w/ alleles for characteristics in middle of range more likely to survive
- reduces range of possible phenotypes
give an example of stabilising selection
range of fur length:
- in stable climate, having extremes of fur length makes harder to maintain body temp
- less likely to survive…
- allele freq. of average fur length increases
- range of fur length decreases
what is directional selection ?
- change in environment
- individuals w/ alleles for more extreme characteristics more likely to survive
- allele frequency shifts to one side
give an example of directional selection
fur length:
- habitat becomes very cold
- those w/ long fur are more likely to survive
- over time, allele frequency of long fur increases
what is genetic drift ?
alleles being passed on through generations and increasing in frequency, all based on chance
when is genetic drift more of a cause of evolution than natural selection ?
in small populations, where chance has a greater influence
what is genetic bottleneck ?
- event occurs, greatly reducing population
- reduction in gene pool
- allele frequency changes
- genetic drift has a greater effect
what is the founder effect ?
- some individuals start new population
- by chance, most are one particular genotype
- new pop. will grow w/ reduced genetic variation
- more heavily influenced by genetic drift as is small pop.
what does the Hardy-Weinberg principle predict ?
predicts frequency of alleles in a population won’t change from one generation to next
what are the certain conditions for Hardy-Weinberg principle to be true ?
- large population
- no immigration / natural selection / mutations
- random mating
what can Hardy-Weinberg principle be used to calculate ?
estimate allele and genotype frequency within population
Hardy-Weinberg principle allele frequency equation :
p + q = 1
what do p and q stand for in Hardy-Weinberg principle
p : frequency of dominant allele
q : frequency of recessive allele
Hardy-Weinberg principle genotype freq. equation :
p^2 + 2pq + q^2 = 1
what do p^2 / 2pq / q^2 stand for in Hardy-Weinberg principle
p^2 : frequency of homozygous dominant genotype
2pq : frequency of hetrozygous genotype
q^2 : frequency of homozygous recessive genotype
outline the process of artificial selection for dairy cattle
- female w/ high milk yield selected
- male w/ mother w/ high milk yield selected
- mate together
- select offspring w/ highest milk yields and breed
- continued over generations
outline the process of artificial selection for wheat plants
- wheat plants w/ high wheat yield bred together
- offspring w/ highest yields bred together
- continued over generations
what is bad about artificial selection ?
- reduces gene pool
- less genetic variation so may be more susceptible to disease / drought
- useful allele for medicine may be lost
define species
group of similar organisms that can reproduce to give fertile offspring
what is speciation ?
development of new species
what causes speciation ?
reproductive isolation
what is allopatric speciation and how does it occur ?
- geographical isolation (physical barrier) divides population
- different conditions favour different characteristic
- mutations occur independently
- allele frequency changes leads to phenotype frequency changing
- no longer able to interbreed and produce fertile offspring
state the ways reproductive isolation occurs
- geographical isolation
- breeding seasons different times
- mechanical changes (genitals dont fit)
- behavioral (different courtship rituals)
what is sympatric speciation ?
speciation as a result of mutations
give an example of sympatric speciation
- mutation occurs, increasing no. of chromosomes
- polyploid may reproduce asexually, if so, a new species may form
