Define indicator species.

Indicator species may be affected by biomagnification. Discuss biomagnification using a named example of a pollutant.

Determine whether islands are open or closed ecosystems.

organism that is present/absent when specific environmental conditions exist
OR
organism used to assess a specific environmental condition

a. example  eg: DDT / mercury / cadmium

b. substance accumulates in «fat» tissue/not excreted «when consumed» 

c. contaminated organisms consumed «in large quantities» by higher level consumers 

d. pollutant becomes more concentrated at each higher trophic level / through the food chain 

e. some pollutants are more likely to be biomagnified «accumulate in fat tissue»
OR
some organisms are more likely to be affected by biomagnification than others
OR
biomagnification not the same at each trophic level 

Only [2] if verified example not given.

closed because islands do not exchange matter/nutrients with surroundings
OR
open because islands do exchange matter/nutrients with surroundings