evolution may lead to speciation

Question 1

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

Answer 1

genetic factors
envi factors like food available
mutations - crossing over between HC during meiosis
indépendant segregation of HC during meiosis
random fertilisation of gametes during sexual reproduction

Question 2

evolution

Answer 2

change in allele freq over time or generations in a population
occurs through process of natural selection

Question 3

what drives natural selection

Answer 3

predation
disease
competition for means of survival
so different survival and reproduction

Question 4

principles of natural selection in evolution of populations

Answer 4

random gene mutation
new allele of gene
due to selection pressures new allele may benefit possessor so organism has selective advantage
advantageous allele inherited by members of next generation
over many generations allele frequency increases in gene pool

Question 5

stabilising selection

Answer 5

Organisms with alleles coding for average trait have a selective
eg. babies with an average weight
So frequency of alleles coding for average
variations of a trait increase and those coding
for extreme variations of a trait decrease
range standard deviation is reduced

Question 6

directional selection

Answer 6

Organisms with alleles coding for one extreme
variation of a trait have a selective advantage
(eg. bacteria with high resistance to an antibiotic)
So frequency of alleles coding for this extreme
variation of the trait increase
those coding for the other extreme variation of the trait decrease

Question 7

disruptive selection

Answer 7

Organisms with alleles coding for either extreme
variation of a trait have a selective advantage

So frequency of alleles coding for both extreme
variations of the trait increase
those coding for the average variation of the trait decrease
This can lead to speciation

Question 8

speciation

Answer 8

reproductive separation of two populations
due to accumulation of differences in their gene pools
new species arise when these genetic differences lead to inability of members of populations to interbreed and produce fertile offspring

Question 9

allopatric

Answer 9

population split bc of geographical isolation
reproductive isolation separating gene pools preventing interbreeding and gene flow between populations
random mutations - genetic variation within each population
so Dif advantageous alleles selected for in each population
allele freq within each gene pool changes over many generations
so Dif pop cant interbreed to produce fertile offspring

Question 10

sympatric

Answer 10

not geo isolated
mutation = reproductive isolation seperating gene pools and preventing interbreeding within one population
eg Dif breading seasons or courtship behaviours or body shapes
Dif selection pressures on each population
so Dif adv alleles are selected for
so allele frequencies within each gene pool change over many generations
eventually different populations cant interbreed to produce fertile offspring

Question 11

genetic drift

Answer 11

mechanism of evolution
allele frequencies in pop change over generations due to chance
some alleles passed onto offspring more or less often by chance
regardless of selection pressure or whether alleles give selective adv
so stronger in small pop as gene pool small - chance has greater influence
bottle neck or founder effect eg
reduces genetic diversity some alleles fixed or lost entirely