| Date | May 2015 | Marks available | 4 | Reference code | 15M.3.SL.TZ2.12 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Discuss | Question number | 12 | Adapted from | N/A |
Question
Discuss the endosymbiotic theory for the origin of eukaryotes.
Markscheme
a. microorganisms/prokaryotes taken into cell by endocytosis;
b. kept inside cell and perform respiration/photosynthesis;
c. developing into mitochondria/chloroplasts;
d. mitochondria/chloroplasts have double membranes (as expected in cells taken in by endocytosis);
e. mitochondria/chloroplasts have (circular naked) DNA (as prokaryotes);
f. mitochondria/chloroplasts have 70S ribosomes (as prokaryotes);
g. mitochondria/chloroplasts grow and divide like (prokaryotic) cells;
Examiners report
Most candidates scored some points in questions 11 and 12 with the top candidates achieving full marks.
