Founder Effect + Bottleneck Effect

Question 1

Describe First Step in Founder Effect

Mainland description

Answer 1

A mainland posseses a population with genetic variation (different alleles present)

Question 2

Describe Second step in Founder Effect

Colonisation

Answer 2

Few individuals from mainland population colonise/migrate an isolated area. They are physically isolated with no gene flow and are thus genetically isolated

Colonisation may have occurred by chance and luck.

Question 3

Describe Third step in Founder Effect

Allele Frequency on Colony

Answer 3

There may be a higher frequency of a particular allele in the founder population just by chance. Founder population may have non-representing sample of alleles from parent population.

Most common allele in founder pop may not be most common on mainland.

Question 4

Describe Fourth step in Founder Effect

After few generation

Answer 4

Founder population grows in size over generations without any gene flow. Allele in low frequency is at risk of genetic drift, if individual fails to carry offspring carrying allele.

Question 5

Describe Fifth step in Founder Effect

Genetic Drift occurs

Answer 5

Genetic drift occurs, low frequency allele is lost completely. Individual that carries it may have failed to have offspring carrying allele or could have died by chance.

Question 6

Describe Sixth step in Founder Effect

Mutations

Answer 6

After a few generations, mutation may occur creating a new allele.

Question 7

Describe Seventh step in Founder Effect

Beneficial mutation

Answer 7

After a few generations, new allele increases in frequency as mutation is not harmful (is beneficial).

Question 8

Describe Eight step in Founder Effect

Comparing the population

Answer 8

Founder population may evolve quite differently from parent population, especially if environment is different

Question 9

What are population bottlenecks?

Answer 9

Ecological events that may reduce sizes of population dramatically

Question 10

How ar population bottlenecks caused?

Answer 10

Bys disasters that are unselective (alleles cannot protect you), such as earthquakes, floods, fire, etc.

Question 11

What is the effect of population bottlenecks on genetic diversity?

Answer 11

Reduces genetic diversity and some alleles may be completely eliminated by chance.

Question 12

How does the new population compare to old one?

3 points

Answer 12

• New population is significantly smaller in number
• Diffferent allele frequencies in population
• Surviving population is unlikely to be representative of old population
• Some alleles may be overrepresentated whilst others may be entirely eliminated

Question 13

Describe the effect of surviving population on future generations

Answer 13

Low numbers in surviving population, teherfore few alleles and hence low genetic diversity. Survivors breedand numbers increase. Low genetic diversity remains since today’s organisms have inherited their alleles from the small numbers available from surviving population

Question 14

State 4 similarities between founder effect and bottlenecking effect

Answer 14

1. Both are followed by genetic drift which changes allele frequencies because of small populations.
2. Initially, genetic diversity is lost/reduced
3. Both involves small number of individuals breeding with each other (and may involve inbreeding)
4. Both may result in new population whihc carries alleles that are unlikely to be true representationof original group

Question 15

State key difference between bottleneck effect and founder effect

Answer 15

In bottleneck effect, individuals are killed (by disaster) whilst in founder effect individuals are separated (geographically)