Explain the phenomenon of “biological magnification.” How does it affect organisms belonging to different trophic levels particularly the tertiary consumers ?
Explain the phenomenon of “biological magnification.” How does it affect organisms belonging to different trophic levels particularly the tertiary consumers ?
Biological magnification is the phenomenon where non-biodegradable chemicals, such as pesticides, accumulate progressively at each successive trophic level in a food chain.
- Entry into Food Chain: Chemicals used to protect crops are washed into the soil or water bodies. From the soil, they are absorbed by plants along with water and minerals; from water bodies, they are taken up by aquatic plants and animals.
- Progression: Since these chemicals are not degradable, they are not excreted or broken down. Instead, they are passed from one trophic level to the next.
- Effect on Tertiary Consumers: Because energy decreases at each level but the chemical amount remains constant or concentrated, the concentration of these chemicals increases at each step. As tertiary consumers (or humans) occupy the top level of the food chain, they accumulate the maximum concentration of these harmful residues in their bodies.
Marking Scheme
- 1Definition of biological magnification as the progressive accumulation of non-degradable chemicals. (1 mark)
- 2Explanation of how chemicals enter the food chain through producers and move through trophic levels. (1 mark)
- 3Explanation of why tertiary consumers/top levels have the maximum concentration. (1 mark)
Hint
Think about why non-biodegradable substances like pesticides don't leave the body and what happens to their concentration as they move from plants to top predators.
Quick Oral Answer
Biological magnification is the increase in the concentration of harmful non-biodegradable chemicals like pesticides as we move up the food chain. Tertiary consumers are most affected because they sit at the top of the chain, meaning they consume all the accumulated toxins from the levels below them.
Analysis & Explanation
According to the NCERT text, biological magnification occurs because certain chemicals used in agriculture (like pesticides) are non-degradable. When producers (plants) absorb these chemicals, they enter the biotic environment. As herbivores eat plants, and carnivores eat herbivores, these chemicals are transferred. Because the chemicals cannot be metabolized or excreted effectively, their concentration per unit of biomass increases as we move up the trophic levels. The text specifically highlights that humans, being at the top of many food chains, end up with the highest concentrations, which is why food grains like wheat and rice often contain pesticide residues that cannot be removed by washing.
Common Mistakes
- 1Confusing biological magnification with energy flow (energy decreases, but chemical concentration increases).
- 2Assuming chemicals can be removed by washing the food.
- 3Stating that biodegradable substances cause magnification (only non-biodegradable ones do).
Interesting Facts
Even if we stop using certain pesticides today, they can persist in the environment and food chains for decades because they are non-biodegradable.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2010?
This question carries 3 marks in the CBSE Class 10 Science 2010 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Our Environment" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Biological Magnification" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2010 paper?
This is a Short Answer question from Section B in the CBSE Class 10 Science 2010 paper.