Question 20N.2.SL.TZ0.b
| Date | November 2020 | Marks available | [Maximum mark: 5] | Reference code | 20N.2.SL.TZ0.b |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Describe | Question number | b | Adapted from | N/A |
Describe the changes that occur in gene pools during speciation.
[5]
a. gene pool is all genes/alleles in an (interbreeding) population;
b. gene pool splits/divides/separated during speciation;
c. due to reproductive isolation (of groups within a species);
d. temporal/behavioral/geographic isolation (can cause reproductive isolation);
e. divergence of gene pools;
f. allele frequencies change;
g. natural selection different (in the isolated groups so there is divergence);
h. different (random) mutations occur (in the isolated populations so there is divergence);
i. speciation has occurred when differences between populations prevent interbreeding;
Do not award both mpc and mpi for the same idea (reproductive isolation separating populations vs speciation due to interbreeding not being possible).
Answers to this part of the question were mostly poor. Gene pools and speciation are the subject of sub-topic 10.3, but many candidates struggled to link these two concepts. Various misunderstandings were seen. As in previous exams, some candidates thought that speciation is evolutionary change over time in a species, rather than the splitting of a species into two or more separate species. Mutations were sometimes described as though they happen in response to a need for new traits, rather than them happening spontaneously and occasionally being selected for.
