Question

Biomagnification refers to an increase in the concentration of the toxicant at successive trophic levels. This happens because
A. A toxic substance accumulated by an organism cannot be metabolized
B. A toxic substance accumulated by an organism cannot be excreted
C. A toxic substance passed on to the next highest trophic level
D. All of the above

Answer 1

Hint: Biomagnification also known as biological magnification is the phenomena of increase in the concentration of the toxicant at each trophic level. This is commonly seen in aquatic food chains where the animals are found in water and water acts as a source of toxicant.

Complete Answer:
Biomagnification (also termed as bio amplification) in toxicology terms defined as the increase in concentration of the substance that is toxic to the individual like pesticide at the successive trophic levels in a food chain. It happens because toxic substances are accumulated in an organism but cannot be metabolized or excreted by the body and therefore passed to the next higher trophic level which feeds on them.

The correct option is D i.e. all of the above.

Note: Biomagnification is most commonly seen in case of mercury or pesticide like DDT. The pathway by which the biomagnification takes place in the food chain is as follows:
- Water having a concentration of DDT 0.003 ppb.
- Zooplankton consumed that water thus the concentration increases to 0.04 ppm.
- Small fishes that feed on that zooplankton have concentration 0.5 ppm.
- Large fishes that feed on these small fishes have a concentration of 2 ppm.
- Finally, fish-eating birds that feed on large fishes have a concentration of 25 ppm.
- The level of DDT present in fish eating birds is enough to cause toxicity in them and for disturbing calcium metabolism in birds which is responsible for the production of thin shelled eggs that eventually cause the decline in bird population.
- It mainly occurs due to the disposal of untreated effluent of industries directly into the water bodies.