Question

The range of biomagnification of DDT in an aquatic food chain, if starting from 0.003 ppb level in water may go at fish-eating bird level upto:
a. 0.3 ppm
b. 3.0 ppm
c. 25.0 ppm
d. 0.003 ppm

Answer 1

Hint: Biological magnification is the process by which harmful substances enter into our food chain and its concentration increases while moving from each trophic level. Biological magnification or simply biomagnification starts mostly with the aquatic food chain where harmful toxins enter through the water bodies (industrial waste, sewage, etc.) inside aquatic organisms.

Complete answer:
There are so many toxic substances present in our environment such as harmful gases from the burning of fossil fuels, industrial and domestic wastes containing nitrogen and phosphorus, etc. These toxic substances which are present in our environment could enter our bodies.

When the toxic substances enter into the aquatic food chain, they get accumulated in the body of the organisms and cannot be excreted out, and in this way pass from one trophic level to the next trophic level. The concentration becomes highest at the maximum level. When the toxic substances get deposited into the organisms of higher trophic levels, it is called bio-accumulation.

DDT stands for dichlorodiphenyldichloroethane and is an insecticide. Insecticides are non-degradable substances; hence tend to move into the organisms. Their concentration increases in each successive tropical level. The concentration of DDT starts at 0.003 ppb (parts per billion) in the water. When it moves up in each tropical level, its concentration increases through biological magnification and reaches up to 25 ppm (parts per million) in fish-eating birds.

Hence, the correct answer is option (C).

Note: When the concentration of DDT increases in birds, it leads to disturbance in calcium metabolism causing changes in the eggshell (thinning) and sometimes premature hatching causing the death of the newborns.