Question 19N.3.SL.TZ0.11c
| Date | November 2019 | Marks available | [Maximum mark: 4] | Reference code | 19N.3.SL.TZ0.11c |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Ensuring the delivery of water to homes requires a pressure to be maintained in the pipes. Biofilm formation will reduce the pressure in the pipes. Three experimental water piping systems were set up and the water was treated before entering the system in one of the following three ways:
• untreated water (Control)
• ultrafiltration (UF) filters particles <500 nm
• nanofiltration (NF) filters particles <1 nm.
The drop in pressure of the water coming out of the tap at the end of the system compared to the pressure of water entering the system was measured.
[Source: reprinted from Water Research, 47(8), G. Liu, M.C. Lut, J.Q.J.C. Verberk, J.C. Van Dijk, A comparison of additional
treatment processes to limit particle accumulation and microbial growth during drinking water distribution, pp 2719–2728,
Copyright (2013), with permission from Elsevier ]
Some biological systems show emergent properties. Emergent properties arise from the interaction of the component parts of a system that are not predictable from studying the individual components.
Explain how biofilms show emergent properties.
[4]
a. biofilms are composed of different species of bacteria/communities of microbes ✔
b. ‹biofilms› form an extracellular film/slime/EPS/exopolipeptide/exopolysaccharides ✔
c. microbes of biofilms show coordination/cooperation/quorum sensing ✔
d. individual microbes have a greater chance of survival in the biofilm «than on their own» ✔
e. biofilms have antibiotic resistance ✔
f. there are exchanges of nutrients between the microbes which is not possible for individual cells ✔
