Population and genetics - Genetic drift

What do allopatric and sympatric speciation rely on?

Mutations occurring within individuals in populations

Why can speciation supposedly not happen without mutations?

There would be no alleles for selection to act upon (everything would be just as likely to survive)

Can speciation/evolution happen without mutations/different selection pressures?

Yes

What is it called when speciation/evolution occurs without mutations/different selection pressures?

Genetic drift

Define genetic drift.

Change in allele frequency in a population as a result of chance, not selection pressures

Is genetic drift more likely to have an impact on smaller or larger populations?

Smaller

Why does genetic drift affect smaller populations more?

Chance has a greater effect on which alleles are passed on. This is because chance variations in big population usually even out. Instead larger populations favour natural selection

Give an example of genetic drift.

1. There is a small population of plants growing near a playground with a rubber floor

2. Half of the plants have alleles for blue flowers, half of the plants have alleles for pink flowers

3. By chance, most of the seeds from the pink-flowered plants end up on the rubber floor of the playground, whereas all the seeds from the blue-flowered plants land on fresh fertile soil where they are able to germinate and grow

4. Over several generations, the alleles for the pink flowers may disappear from this population