Date | May 2012 | Marks available | 1 | Reference code | 12M.3.SL.TZ2.21 |
Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
Command term | State | Question number | 21 | Adapted from | N/A |
Question
Explain how living organisms can affect the abiotic environment during primary succession.
State one example of biological control of an invasive species.
Invasive species: ......................................................
Biological control: ......................................................
Define biomagnification.
Markscheme
remains/debris/litter from growth/death of plants can increase soil depth;
remains/debris/litter from growth/death of plants can increase soil mineral content;
remains/debris/litter from growth/death of plants can alter soil pH;
remains/debris/litter from growth/death of plants can improve soil water retention and reduce drainage;
growth of (larger) plants can reduce erosion though binding action of roots;
example of invasive species and an example of its biological control
e.g.:
prickly pear cactus is controlled by moth (Cactoblastis cactorum)
Accept other suitable example.
a process when chemical substances become more concentrated at each trophic level
Examiners report
Many candidates did not know how plants affected the environment in a primary succession.
Many incorrect answers. Some candidates invented examples of biological control. In some cases, the candidate mentioned an invasive species and then a different example of biological control.
In (c) Most candidates could define biomagnification.