7.3

Question 1

why do individuals within population of species show wide range of variation in phenotype

Answer 1

genetic factors
mutation
crossing over between hc during meiosis or independent segregation
random fertilisation of gametes during sexual reproduction
envi factors

Question 2

evolution

Answer 2

change in allele frequency overtime in many generations in a population
occur through natural selection

Question 3

factors driving natural selection

Answer 3

predation disease and competition for means of survival
result in different reproduction and survival

Question 4

principles of natural selection in evolution of populations

Answer 4

random gene mutation result in new alleles of gene
due to selection pressure the new allele may benefit possessor so organism has selective advantage
possesor more likely to survive and have increased reproductive success
advantageous allele inherited by offspring
over many generations allele increases in frequency in gene pool

Question 5

stabilising selection

Answer 5

organism w allele coding for average allele of trait have selective advantage
so freq of alleles coding for average variation of trait increase and those coding for extreme decrease
range and standard deviation reduced

Question 6

directional selection

Answer 6

organism w allele coding for one extreme variation of trait have selective advantage
so this freq of alleles increase but those coding for other extreme variation of trait decreases

Question 7

disruptive selection

Answer 7

organism coding for allele for either extreme variation of trait have a selective advantge
so freq of alleles coding for both extreme variations of trait increase and those coding for average decreases
can lead to speciation

Question 8

speciation

Answer 8

how new species arise from existing species
reproductive separation of 2 populations
result in accumulation of differences in their gene pools
new species arise when these genetic differences lead to inability of members of population to interbreed and produce fertile offspring

Question 9

allopatric speciation

Answer 9

population split bc of geographical isolation
leads to reproductive isolation seperating gene pools by preventing interbreeding between populations
random mutation cause genetic variation within each population and different selection pressures
so different advantageous alleles passed on - allele frequencies within each population change over generations
Eventually lead to different populations that cant interbreed to produce fertile offspring

Question 10

sympatric speciation

Answer 10

population not geographically isolated
mutation leads to reproductive isolation separating gene pools by preventing interbreeding eg different courtship behaviours
different breading seasons
gamete incompatibility
different selection pressures act on each population
so different advantageous alleles are selected for and passed on I each population
so allele frequencys within each gene pool change over many generations
eventually cant interbreed to produce fertile offspring

Question 11

genetic drift

Answer 11

mechanism of evolution in which allele frequencies in population change over many generations due to chance
as some alleles are passed onto offspring more or less by chance regardless of selection pressures and whether alleles give selective advantage or not
strongest effects in small population as gene pool is small and chance has a greater influence
this can reduce genetic diversity as some alleles can be fixed or lost entirely