7.3 Evolution

Question 1

Why may individuals show a range of variation

Answer 1

Genetic factors:
-mutation
-crossing over (meiosis)
-independent segregation (meiosis)

Environmental factors:
-food availability
-light
-etc

Question 2

What is evolution

Answer 2

Change in allele frequency over time (many generations)

Occurring though natural selection

Question 3

Factors that may drive evolution

Answer 3

Predation
Disease
Competition

Question 4

Principles of natural selection in evolution of pops

Answer 4

MARIA

mutations - can result in new alleles

Advantages - allele may benefit its predecessor so will have a select advantage

Reproduction- increase in reproductive success

Inheritance - advantageous alleles is passed down to the next generation

Allele freq- allele freq is increased

Question 5

Effects of stabilising selection

Answer 5

Organisms with average variations have an advantage

So freq of alleles coding for that average variation increase and those coding for extreme decrease

So range/SD is decreased

Question 6

Directional selection

Answer 6

Organisms coding for extreme variations have a selective advantage

So the freq of the allele increases and those coding for the other extreme decrease (graph moves left or right)

Question 7

Disruptive selection

Answer 7

Organisms coding for either extreme have selective advantage

So freq of both alleles increases

So coding for average variation decreased

Leading to speciation

Question 8

What is speciation

Answer 8

Reproductive separation of 2 pops

Results in accumulation of differences in their gene pools

New species arise when the genetic difference can no longer breed to produce fertile offspring

Question 9

Allopatric speciation

Answer 9

Pop soil due to geographical isolation

Reproductive isolation, separate gene pools by preventing interbreeding

Random mutations (genetic variation)

Different selection pressures( environment acts on pop)

So different advantage alleles

So allele freq per gene pool changes over many generations

Species can’t interbreed

Question 10

Sympathetic speciation

Answer 10

Pop isn’t geographically isolated

Mutations lead or reproductive isolation, separating gene pools (no interbreeding) e.g. could be different breeding seasons

Diffrent selection pressures for each pop

Different advantages alleles for each pop

Allele freq will change over many generations

Populations can’t interbreed

Question 11

What is genetic drift

Answer 11

Mech of evolution in which allele freq in a pop will change over time due to chance

Question 12

Why is genetic drift more important in small populations

Answer 12

Alleles are passed more/loss often by chance

So strongest effects in a small pop with no interbreeding with other populations (chance has a greater influence)

Can reduce genetic diversity -some alleles will have a high frequency