The correct answer is A.
Toxins and various pollutants increase in concentration through the food chain in a process called biomagnification. This means that the organisms on the top of the food chain, like the herring gull, have many times greater concentration of toxins than the lower food chain level organisms because they prey on lower food chain level organisms. If a herring gull ears 100 herrings, it will have a 100x times greater concentration of toxins in its body than a herring.
The correct answer is option D, Temporal isolation
Temporal isolation is the mechanism which prevents the mating of closely related species living in the same ecosystem. Basically the reproductive barriers prevent these species from interbreeding. Temporal isolation is a prezygotic barrier that causes “time isolation” between the breeding period of two closely related species. The difference in time could be “difference in time of day”, “ difference in season of mating”, “difference in months” and in some cases “ difference in years”.
Biodiversity is essential in medicine as most active chemicals used to make medicines are derived from plants or other organisms. Climate change today threatens species that are vital to medicine. An example would be coral reefs. Studies have been done on reefs that look at fighting cancers, HIV and other ailments. One of the richest zones of biodiversity is the tropics and this region is under threat from global warming and deforestation. It is important to preserve these species for use in future medicinal research. <span />
