| Date | May 2015 | Marks available | 3 | Reference code | 15M.3.SL.TZ1.11 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Discuss | Question number | 11 | Adapted from | N/A |
Question
The diagram shows some of the later stages in the origin of eukaryotic cells according to the endosymbiotic theory.
Discuss the endosymbiotic theory including the evidence for the process shown in the diagram.
Markscheme
a. ancestral eukaryote cell engulfs free living prokaryote;
b. free living prokaryote not digested;
c. symbiotic relationship develops between ancestral eukaryote cell and engulfed prokaryote;
d. ancestral eukaryote cell and engulfed prokaryote reproduce as a unit;
e. the engulfed prokaryote provides energy by aerobic respiration for the eukaryote;
f. prokaryote gains protection/nutrition;
g. organelles have double membranes;
h. organelles have DNA/ribosomes;
i. theory cannot be falsified/tested;
Examiners report
There was sound knowledge of endosymbiosis
