| Date | May 2013 | Marks available | 4 | Reference code | 13M.3.SL.TZ1.12 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
Compare convergent and divergent evolution.
Explain how polyploidy can contribute to speciation.
Markscheme
Reject unqualified statements to the effect that both are types of evolution.
Polyploidy:
a. having more than 2 (complete) chromosome sets/description of polyploidy;
b. happens through chromosome mutation / non-disjunction;
c. occurs more frequently in plants than animals;
Contribution to speciation
d. polyploids cannot reproduce with original species / meiosis fails / chromosomes cannot pair;
e. creates reproductive barrier;
f. but can self-fertilize / reproduce with similar individuals;
g. thus forming a new species;
h. new species formed by sympatric speciation;
Examiners report
D3 (a) was reasonably answered by most candidates, though many answers in (b) were very vague.
D3 (a) was reasonably answered by most candidates, though many answers in (b) were very vague.
