| Date | November 2016 | Marks available | 3 | Reference code | 16N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
| Command term | Suggest | Question number | 14 | Adapted from | N/A |
Question
Cryptococcus neoformans and the closely related species Cryptococcus gattii are human fungal pathogens. The reproduction of these yeast species on increasing concentrations of pigeon droppings (PD) was examined to determine whether they occupy the same or different ecological niches. The results for reproduction are expressed as a percentage relative to the control.
Suggest how this experiment shows that pigeon droppings represent a realized ecological niche for C. neoformans and a fundamental (but not a realized) niche for C. gattii.
Markscheme
a. the realized niche is the actual while the fundamental niche is «all of» the potential
b. «shared» fundamental niche shown by equal reproduction on control
c. C. neoformans reproduces on PD indicating a realized ecological niche
d. competitive exclusion decreases realized niche of C. gattii
e. C. gattii reproduces poorly on PD representing a fundamental niche
OR
C. gattii reproduces poorly on PD so not a realized niche
