Use of pesticides to protect our crops affect organisms at various trophic levels especially human beings. Name the phenomenon involved and explain how does it happen.
Use of pesticides to protect our crops affect organisms at various trophic levels especially human beings. Name the phenomenon involved and explain how does it happen.
The phenomenon involved is biological magnification.
How it happens:
- Entry into the Food Chain: Pesticides and chemicals sprayed on crops are washed down 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.
- Progressive Accumulation: Since these synthetic chemicals are non-degradable, they cannot be broken down by the metabolic activities of organisms. Consequently, they get accumulated progressively at each higher trophic level.
- Maximum Concentration in Humans: Because human beings occupy the top level in almost all food chains, the maximum concentration of these harmful chemicals gets accumulated in our bodies over time.
Marking Scheme
- 1Naming the phenomenon as 'biological magnification' (1 mark)
- 2Explaining how chemicals enter the food chain (absorption by plants from soil/water) (1 mark)
- 3Explaining progressive accumulation at higher trophic levels and why humans get the maximum concentration (1 mark)
Hint
Recall the term for the progressive accumulation of non-degradable chemicals at higher trophic levels, especially in top consumers like humans.
Quick Oral Answer
The phenomenon is biological magnification. It occurs when non-degradable chemicals like pesticides enter the food chain through plants and accumulate progressively at each higher trophic level, reaching the highest concentration in top consumers like humans.
Analysis & Explanation
As explained in the NCERT textbook, pesticides used to protect crops are non-degradable. When they enter the soil or water bodies, they are absorbed by producers (plants). As energy and organic matter flow from one trophic level to the next, these non-degradable chemicals do not get excreted or broken down; instead, they accumulate. Since the biomass decreases at higher trophic levels but the chemical amount persists, the concentration of these chemicals increases progressively at each trophic level. Since humans are omnivores occupying the highest trophic level in many food chains, we end up with the highest concentration of these toxic residues in our bodies, a process known as biological magnification.
Common Mistakes
- 1Calling the phenomenon 'eutrophication' or 'bioaccumulation' instead of 'biological magnification'.
- 2Failing to explain *why* the concentration increases (i.e., because the chemicals are non-degradable and accumulate progressively).
- 3Not mentioning that humans occupy the top level of the food chain.
Interesting Facts
Pesticide residues in food grains like wheat and rice, or in fruits and vegetables, cannot always be removed by washing because these chemicals are absorbed internally by the plants during growth.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2024?
This question carries 3 marks in the CBSE Class 10 Science 2024 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 2024 paper?
This is a Short Answer question from Section C in the CBSE Class 10 Science 2024 paper.