| Date | May 2015 | Marks available | 2 | Reference code | 15M.3.HL.TZ1.2 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Outline | Question number | 2 | Adapted from | N/A |
Question
Outline the endosymbiotic theory.
[2]
b.
Define gene pool.
[1]
c (ii).
Markscheme
a. mitochondria/chloroplasts were once (independent) prokaryotes;
b. taken in by (larger) heterotrophic/host cell (through endocytosis);
c. new living arrangement mutually beneficial / depend on each other to exist as single organism;
b.
all the alleles/genes of a population (at a particular time)
c (ii).
Examiners report
While many candidates were able to get 1 mark, and some 2, few wrote clearly or accurately about the endosymbiotic theory. The question was not asking for evidence of the theory which is what some candidates wrote about.
b.
The definition of gene pool in (ii) was answered better than in previous years.
c (ii).
