evolution may lead top speciation

Question 1

1. What is a gene pool?

Answer 1

All the alleles of all the genes in a population;

Question 2

2. What causes the variation in the phenotypes of a species?

Answer 2

The different alleles in the population and the impact of the environment. Mutations may also occur to cause variation.

Question 3

3. What is the primary cause of genetic variation?

Answer 3

All alleles are the result of mutations in the past.

Question 4

4. What are other causes of genetic variation?

Answer 4

Mutation; Independent assortment and crossing over in meiosis; random fertilisation of gametes during sexual reproduction;

Question 5

5. What can result in differential survival and reproduction within a population?

Answer 5

Predation, disease and competition for resources.

Question 6

6. What is the effect of stabilising selection?

Answer 6

The extreme phenotypes are selected against (removed); which reduces the frequency of alleles for extreme phenotypes;

Question 7

7. What is the effect on allele frequency of directional selection?

Answer 7

A mutation occurs that gives an advantage; organisms with the advantageous allele are more likely to survive and breed; the offspring are more likely to inherit the allele; the frequency of the allele increases in the population;

Question 8

8. What can disruption selection cause to happen over time?

Answer 8

Speciation may occur; if the two populations are reproductively isolated; and they have different selection pressures meaning organisms with different alleles are selected for and passed on to offspring; eventually the two populations cannot interbreed to produce fertile offspring.

Question 9

9. Describe the process of allopatric speciation..

Answer 9

Geographical isolation; Different selection pressures in the separated populations due to different biotic (food, competition) and abiotic (environment, climate); Variation in alleles due to mutation; Individuals with advantageous alleles are more likely to survive and reproduce passing these alleles to their offspring; The frequency of the advantageous alleles increases in the future generations; The frequency of advantageous phenotype increases in the future generations; No interbreeding with the other population, separate gene pool.

Question 10

10. Describe the process of sympatric speciation.

Answer 10

Variation of alleles between individuals due to mutation (link back to characteristic discussed in question); Occurs in the same habitat (no geographical isolation); Reproductive isolation occurs (due to changes in courtship behaviours, changed behaviours etc). Different selection pressures on different populations; Different alleles passed on to offspring, causing a change in the frequency of alleles; so no gene flow between individuals with and without allele. Eventually populations become genetically different and so cannot interbreed to produce fertile offspring.

Question 11

11. What is genetic drift?

Answer 11

A change in the allele frequency in small populations due to the chance disappearance of particular alleles as individuals die or do not reproduce.

Question 12

12. Why is genetic drift only important in small populations?

Answer 12

Larger populations have a wider variety of alleles, and individuals have more chance of reproducing with individuals that possess different alleles from them. Decreasing the likelihood of genetic drift.

Question 13

13. What is evolution

Answer 13

A change in the allele frequency over time

Question 14

14. By what process does evolution occur by?

Answer 14

Natural selection

Question 15

15. What are the three types of natural selection?

Answer 15

Directional, disruptive, stabilising.