Speciation

Question 1

What is speciation?

Answer 1

The development of a new species from an existing species.

Question 2

When does speciation occur?

Answer 2

When one population of the same species becomes reproductively isolated. This means that there are now two populations of the same species and they can’t breed together. This leads to an accumulation of differences in their DNA meaning they can no longer interbreed and produce fertile offspring.

Question 3

What is allopatric speciation?

Answer 3

The formation of a new species due to the formation of a physical barrier.

Question 4

How does allopatric speciation occur?

Answer 4

1. Geographical isolation
2. Variation due to mutation.
3. They will experience different selection pressures.
4. They will have different adaptations that will help them survive and reproduce.
5. This leads to a change in allele frequency and may mean that the two populations will no longer be able to inter breed and produce fertile offspring.

Question 5

What is sympatric speciation?

Answer 5

Speciation that happens without geographical isolation.

Question 6

How does sympatric speciation occur?

Answer 6

This happens with organisms living in the same habitat. A mutation changes something and this leads to reproductive isolation. This means that different alleles are passed on and there’s is no gene flow. Disruptive selection occurs and eventually the different species and no longer interbreed and produce fertile offspring.

Question 7

How do seasonal changes cause reproductive isolation?

Answer 7

If individuals have different mating and flowering seasons they won’t be able to breed together and reproduce.

Question 8

How do mechanical changes cause reproductive isolation?

Answer 8

Changes in the genitalia prevent individuals from breeding and reproducing.

Question 9

How do behavioral changes cause reproductive isolation?

Answer 9

If a group of individuals develop courtship rituals that are not attractive to the main population those individuals won’t be able to bond successfully with the members of the main population.

Question 10

How can different changes in allele frequencies occur in the seperate populations?

Answer 10

1. Natural selection.
2. Mutations.
3. Genetic drift

Question 11

What is genetic drift?

Answer 11

Chance rather than environmental factors dictate the survival, breeding and alleles being passed on.

Question 12

How does genetic drift work?

Answer 12

1. By chance the allele for one genotype is passed on to more offspring than others.
2. This means the number of individuals with that allele increases.
3. If by chance the same allele is passed on more often again and again this leads to evolution.

Question 13

How does population size affect genetic drift?

Answer 13

The smaller the population the bigger the effect of genetic drift because in these populations chance has a greater influence. In larger populations, the effect of chance tends to even out.

Question 14

What are examples of genetic drift?

Answer 14

1. Founder effect.
2. Bootle-neck effect.