Discuss, using three examples, how alien species have impacted ecosystems.

a. the alien species can compete with existing species for resources / interspecific competition with native species;

b. appropriate example for competition with existing species;

c. alien species can be a predator of native species;

d. different appropriate example for predator of native species;

e. alien species can cause extinction of local species;

f. different appropriate example for causing extinction;

g. alien species can be deliberately added for biological control;

h. different appropriate example for biological control;

i. deliberate introduction of alien species for economic/other reasons;

j. different appropriate example for economic/other reasons;

Each impact must have a different example.

Although there were some very good answers, many candidates experienced some difficulty, partly due to poorly organized answers, repeated or vague examples and/or impacts.