Explain the causes and consequences of biomagnification of a named chemical.

Explain the concept of niche.

a. named example of chemical (for example: mercury, DDT, PCBs, TBT, PAHs,heavy metals, selenium);
b. long lived / do not biodegrade / stored in body tissues / fat soluble;
c. present in small concentration in the environment;
d. chemical becomes more concentrated in the bodies of organisms at each successive trophic level;
e. reach toxic levels in top consumer/organisms near the end of the food chain / example of top consumer affected;
Award [2 max] if no named example of chemical.

a. includes all aspects of way of life of a species/role of the species in the ecosystem;
b. includes relationships within the community;
c. feeding relationships;
d. interaction with environment/spatial habitat;

If candidates knew an example of biomagnification they were able to gain the three marks, but even so, many do not understand how and why a chemical becomes more concentrated in each successive trophic level.

The best answers to explaining a niche appeared to be rote-learned, otherwise candidates had difficulty using their own words.