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Q5(b):
Write critical notes on the following:
(b) Biological magnification
Solution :
1. Conceptual Foundation of Biological Magnification
Biological magnification, also known as biomagnification, is defined as the progressive increase in the concentration of non-biodegradable chemical substances—specifically persistent organic pollutants, pesticides (e.g., $DDT$), and heavy metals (e.g., Mercury)—at successive trophic levels in a food chain. [Ref: Trophic Dynamics & Bioaccumulation Theory].
2. The Mechanics of Accumulation
The phenomenon occurs due to three fundamental requirements of the pollutant:
- Persistence: The substance must not be easily degraded by environmental processes or biological enzymes.
- Lipid Solubility: The toxin must be fat-soluble (lipophilic) rather than water-soluble, allowing it to be stored in the adipose tissues of organisms instead of being excreted.
- Bioaccumulation: The rate of intake must exceed the rate of metabolic breakdown or excretion.
3. Mathematical Representation of Biomagnification
Consider a food chain with $n$ levels where $C_n$ represents the concentration of a toxin in an organism at trophic level $n$. If $E$ is the efficiency of transfer (accumulation factor), the concentration at level $n+1$ is given by:
$C_{n+1} = C_n \cdot \frac{I \cdot T}{M \cdot E_{out}}$
Where $I$ = Intake rate, $T$ = Exposure time, $M$ = Metabolic degradation rate, and $E_{out}$ = Excretion rate.
4. Case Analysis: The DDT Mechanism
Dichlorodiphenyltrichloroethane ($DDT$) exemplifies biomagnification. When $DDT$ enters an aquatic ecosystem:
| Trophic Level | Process | Biological Impact |
|---|---|---|
| Primary Producers/Consumers | Minimal ingestion | Sub-lethal accumulation in adipose tissue |
| Apex Predators (Birds) | High-volume consumption | Inhibition of Calcium ATPase, leading to eggshell thinning |
5. Physiological Consequences
The critical danger of biomagnification is that while the environment may show negligible levels of a toxin, the biological impact on the apex predator is catastrophic:
- Endocrine Disruption: Many persistent pollutants act as hormone mimics, causing developmental abnormalities.
- Reproductive Failure: As observed with $DDT$ in birds of prey, shell thinning leads to premature breakage during incubation, causing population declines [Per the Law of Population Ecology].
- Neurotoxicity: Heavy metals like Methylmercury result in severe neurological damage in apex consumers, including humans.
Final Solution: Biological magnification is the exponential rise in tissue-level concentration of non-metabolizable toxins as they move up the food chain, resulting in systemic toxicity and reproductive failure for apex organisms.
More Questions from Class 12 Biology Environmental Issues EXERCISES
- Q1: What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
- Q1: What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
- Q2: List all the wastes that you generate, at home, school or during your trips to other places. Could you very easily reduce the generation of these wastes? Which would be difficult or rather impossible to reduce?
- Q2: List all the wastes that you generate, at home, school or during your trips to other places. Could you very easily reduce the generation of these wastes? Which would be difficult or rather impossible to reduce?
- Q3: Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
- Q3: Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
- Q4: Match the items given in column A and B:
- Q4: Match the items given in column A and B: Column A Column B (a) Catalytic converter (i) Particulate matter (b) Electrostatic precipitator (ii) Carbon monoxide and nitrogen oxides (c) Earmuffs (iii) High noise level (d) Landfills (iv) Solid wastes
- Q5(a): Write critical notes on the following: (a) Eutrophication
- Q5(a): Write critical notes on the following: (a) Eutrophication
- Q5(b): Write critical notes on the following: (b) Biological magnification
- Q5(c): Write critical notes on the following: (c) Groundwater depletion and ways for its replenishment
- Q5(c): Write critical notes on the following: (c) Groundwater depletion and ways for its replenishment
- Q6: Why does ozone hole form over Antarctica? How will enhanced ultraviolet radiation affect us?
- Q6: Why does ozone hole form over Antarctica? How will enhanced ultraviolet radiation affect us?
- Q7: Discuss the role of women and communities in protection and conservation of forests.
- Q7: Discuss the role of women and communities in protection and conservation of forests.
- Q8: What measures, as an individual, would you take to reduce environmental pollution?
- Q8: What measures, as an individual, would you take to reduce environmental pollution?
- Q9(a): Discuss briefly the following: (a) Radioactive wastes
- Q9(a): Discuss briefly the following: (a) Radioactive wastes
- Q9(b): Discuss briefly the following: (b) Defunct ships and e-wastes
- Q9(b): Discuss briefly the following: (b) Defunct ships and e-wastes
- Q9(c): Discuss briefly the following: (c) Municipal solid wastes
- Q9(c): Discuss briefly the following: (c) Municipal solid wastes
- Q10: What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
- Q10: What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
- Q11(a): Discuss briefly the following: (a) Greenhouse gases
- Q11(a): Discuss briefly the following: (a) Greenhouse gases
- Q11(b): Discuss briefly the following: (b) Catalytic converter
- Q11(b): Discuss briefly the following: (b) Catalytic converter
- Q11(c): Discuss briefly the following: (c) Ultraviolet B
- Q11(c): Discuss briefly the following: (c) Ultraviolet B
CBSE Solutions for Class 12 Biology Environmental Issues
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
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