UGC NET Questions (Paper – 1)

Biomagnification occurs when persistent pollutants that are not easily broken down accumulate as they move up food chains. Small organisms take up low concentrations from water, but predators eat many contaminated prey. At each trophic level, the pollutant concentration in tissues becomes higher. The highest levels are often found in top predators, such as fish-eating birds, which is exactly what the correct statement describes.

Option A:
Option A is incorrect because water usually contains relatively low concentrations of DDT compared to living organisms. It is in organisms, not in the water itself, that concentrations tend to build up.

Option B:
Option B is incorrect since saying concentrations decrease at higher trophic levels reverses the observed pattern. That would imply biodilution, not biomagnification.

Option C:
Option C is correct because it shows increasing concentration from plankton to fish and then birds. This pattern explains why eggshell thinning was observed in birds exposed to DDT through aquatic food chains.

Option D:
Option D is incorrect because DDT is known for its persistence and slow breakdown. Its ability to enter and stay in organisms is the reason biomagnification occurs.

Biomagnification occurs when persistent, fat-soluble pollutants accumulate at higher levels in a food chain. Small organisms like plankton take up low concentrations from water, but predators eat many contaminated prey. At each trophic level, the pollutant becomes more concentrated in body tissues, so top predators show the highest levels. The classic example is DDT accumulation from plankton to fish to fish-eating birds.

Option A:
Option A is incorrect because water generally has lower concentration than organisms; pollutants move into and concentrate within living tissues.

Option B:
Option B is incorrect; biomagnification means increasing, not decreasing, concentrations at higher trophic levels.

Option C:
Option C is correct as it describes rising concentration from lower to higher levels, matching observed patterns for DDT and similar pesticides.

Option D:
Option D is incorrect because DDT is persistent and not completely degraded before entering food chains, which is why biomagnification occurs.