| Date | May 2017 | Marks available | 3 | Reference code | 17M.3.SL.TZ2.9 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Explain | Question number | 9 | Adapted from | N/A |
Question
The diagram shows a biofilm that has formed on a tooth.
Using the diagram, explain the concept of emergent properties of biofilms.
Markscheme
a. «in biofilms» bacteria exhibit «emergent» properties not predictable from the individual components of the system
OR
biofilm exhibits its own properties, quite different in comparison with those shown by the single species
b. biofilms form when bacteria adhere to surface of tooth and begin to excrete an EPS/extracellular polymeric substances/exopolysaccharides
c. formation of EPS maintains bacteria together «in biofilm»
d. interspecies relationships are favourable
OR
one species produces growth factors for/facilitates attachment of another species
e. individual forces are low but the overall binding force can exceed that of covalent bonds
f. glue properties/cohesiveness given by different types of bonding
g. biofilms show resistance to antibiotics/other pathogen
