| Date | May 2013 | Marks available | 4 | Reference code | 13M.2.SL.TZ2.3 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 2 |
| Command term | Outline | Question number | 3 | Adapted from | N/A |
Question
List two factors that could cause an increase in the size of an animal population.
1. ..................................................................
2. ..................................................................
Outline how overpopulation of a species in a given environment may lead to evolution.
Markscheme
a. natality / increased birth rate;
b. immigration;
c. extra food/water / breeding sites;
d. expanding habitat;
e. lack of predators/disease/parasites / reduced death rate;
a. more are born than can survive;
b. there is variety/variability in the offspring;
c. competition for resources / struggle for survival / selection pressure;
d. only the most able/adapted survive / survival of the fittest;
e. the survivors reproduce and pass on genes;
f. genes of less able/adapted are eliminated / change in the gene pool;
g. natural selection occurs;
Examiners report
Most of the candidates obtained both marks. Expanding habitat was hardly mentioned.
Many candidates failed to receive points because they often wrongly implied the following: "..competition between species", "survival of the fittest species".
