Answer question numbers 4(a) to 4(d) on the basis of your understanding of the following paragraph and the related studied concepts.
Human body is made up of five important components, of which water is the main component. Food as well as potable water are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.
(a) Why is the maximum concentration of pesticides found in human beings? (1 mark)
(b) Give one method which could be applied to reduce our intake of pesticides through food to some extent. (1 mark)
(c) Various steps in a food chain represent:
(a) Food web
(b) Trophic level
(c) Ecosystem
(d) Biomagnification (1 mark)
(d) With regard to various food chains operating in an ecosystem, man is a:
(a) Consumer
(b) Producer
(c) Producer and consumer
(d) Producer and decomposer (1 mark)
Answer question numbers 4(a) to 4(d) on the basis of your understanding of the following paragraph and the related studied concepts.
Human body is made up of five important components, of which water is the main component. Food as well as potable water are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.
(a) Why is the maximum concentration of pesticides found in human beings? (1 mark)
(b) Give one method which could be applied to reduce our intake of pesticides through food to some extent. (1 mark)
(c) Various steps in a food chain represent:
(a) Food web
(b) Trophic level
(c) Ecosystem
(d) Biomagnification (1 mark)
(d) With regard to various food chains operating in an ecosystem, man is a:
(a) Consumer
(b) Producer
(c) Producer and consumer
(d) Producer and decomposer (1 mark)
(a) Human beings occupy the top level in any food chain. Since pesticides are non-biodegradable, they cannot be broken down by biological processes and instead accumulate progressively at each successive trophic level. This phenomenon is known as biological magnification, resulting in the highest concentration of these chemicals in human bodies.
(b) One method to reduce our intake of pesticides is to adopt organic farming practices (which avoid the use of synthetic chemical pesticides) or to thoroughly wash, peel, and clean food grains, fruits, and vegetables before consumption to remove surface residues.
(c) Correct Option: (b) Trophic level
(d) Correct Option: (a) Consumer
Marking Scheme
- 1For (a): 1 Mark for explaining that humans occupy the top trophic level and non-biodegradable pesticides accumulate progressively (biological magnification).
- 2For (b): 1 Mark for suggesting a valid method like organic farming or washing/peeling produce.
- 3For (c): 1 Mark for identifying 'Trophic level' (Option b).
- 4For (d): 1 Mark for identifying 'Consumer' (Option a).
Hint
Recall that non-biodegradable substances accumulate as we go higher up the food chain, and humans occupy the topmost position. Think about how food chains are structured into different feeding levels.
Quick Oral Answer
Biological magnification is the progressive accumulation of non-biodegradable chemicals like pesticides at each successive trophic level in a food chain, reaching maximum concentration at the top level, which is occupied by humans.
Analysis & Explanation
The case study highlights the concept of biological magnification.
- For (a), the NCERT text states that because these chemicals are not degradable, they accumulate progressively at each trophic level. Since human beings occupy the top level in any food chain, the maximum concentration gets accumulated in our bodies.
- For (b), while the text notes that pesticide residues cannot always be completely removed by washing, surface residues can be reduced by washing and peeling. A more systemic solution is shifting towards organic farming to prevent pesticides from entering the food chain in the first place.
- For (c), the NCERT text explicitly defines: 'Each step or level of the food chain forms a trophic level.'
- For (d), humans cannot synthesize their own food via photosynthesis (producers) nor do they decompose dead organic matter (decomposers). They depend on producers directly or indirectly, making them consumers.
Common Mistakes
- 1Believing that washing completely removes all pesticides (some are absorbed systemically by the plant tissues).
- 2Confusing biological magnification with biodegradation.
Interesting Facts
Because of biological magnification, top predators like eagles and humans often have pesticide concentrations in their bodies that are thousands of times higher than the concentration of those chemicals in the surrounding water or soil.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2020?
This question carries 4 marks in the CBSE Class 10 Science 2020 examination.
What topic does this question cover in Science?
This question covers the topic "Biological Magnification and Trophic Levels" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2020 paper?
This question appears in Section A in the CBSE Class 10 Science 2020 paper.