Question

Phenomenon involved in increasing the concentration of non-degradable pollutants in a trophic level of an ecosystem,
(a) Biodegradation
(b) Biomineralization
(c) Bioaccumulation
(d) Biomagnification

Answer 1

Toxicants get into the body of animals through different pathways. Within the animal body, they may follow two major pathways, biotransformation, and biological magnification. In the former, toxicants get transformed into different chemical forms. But in the latter, they accumulate in the different organs, then enter the food chain and pass to other animals.

Complete step by step answer:
Biotransformation, also called metabolic transformation, is the transformation of a substance from one chemical form to another by the biochemical reaction within the body. Biotransformation of toxicants involves the conversion of harmful toxicants to less harmful metabolites. Biomagnification is the progressive increase in the concentration of a substance, such as a pesticide DDT, from lower to higher trophic levels in a food chain. It is a consequence of the substance. Although sometimes used interchangeably with 'bioaccumulation' an important distinction is drawn between the two. Bioaccumulation occurs within a trophic level and is the increase in the concentration of a substance in an individual's tissues due to uptake from outside. Thus bioaccumulation occurs within an organism, whereas biomagnification occurs across trophic levels. Bioaccumulation and biomagnification result in its build- up in adipose tissue of successive trophic levels such as zooplankton, small nekton, large fish, etc. Other animals that eat these fish also consume the higher levels of mercury accumulated in the fish. This process explains why predatory fishes such as sharks and swordfish or birds like eagles, have a higher concentration of mercury in their tissue.

Additional information:
- Lipid soluble substances cannot be excreted in the urine, which is a water- based medium. So, they accumulate in the fatty tissues of an organism, if the organism lacks enzymes to degrade them.
- When this organism is eaten by another organism, fats are absorbed in the gut, causing the substance to accumulate in the fats of the predator.
- Biodegradation is the process by which organic substances are decomposed by microorganisms such as bacteria into simpler substances such as carbon dioxide, water, and ammonia.
- Biomineralization is the process by which living organisms manufacture minerals for different functional purposes, such as mechanical stiffening of tissue, magnetic or gravitational sensing, and element storage.
So, the correct answer is ‘Biomagnification’.

Note: There are three main groups of substances that biomagnify, namely novel organic substances, metals, and radioactive substances. These are lipophilic and not easily degradable. Novel organic substances are not easily degraded because organisms lack previous exposure and have thus not evolved specific detoxification and excretion mechanisms.