Biomagnification of DDT caused decline in bird population by:

Options

A. bringing disturbance in calcium metabolism
B. thinning of egg small
C. premature breaking of eggs
D. all the above

Answer

**Step-by-Step Solution:**

1. **Understanding DDT**: DDT (Dichloro-Diphenyl-Trichloroethane) is a synthetic pesticide that was widely used for agricultural purposes. It is known for its effectiveness in controlling insect populations.

2. **Biomagnification**: This is the process where certain substances, like DDT, become more concentrated in the tissues of organisms at each successive level of the food chain. When smaller organisms (like insects and fish) absorb DDT, the concentration increases as it moves up the food chain to larger predators (like birds).

3. **Impact on Calcium Metabolism**: DDT disrupts calcium metabolism in birds. Calcium is crucial for the formation of eggshells. When birds are exposed to high levels of DDT, their ability to metabolize calcium properly is impaired.

4. **Thinning of Eggs**: Due to the disturbance in calcium metabolism, the eggs produced by birds become thinner and weaker. Thinner eggs are more susceptible to breakage, which can lead to decreased hatching success.

5. **Premature Breaking of Eggs**: The weakened eggshells can lead to premature breaking of the eggs, either during the incubation period or shortly after laying. This results in fewer chicks surviving to adulthood.

6. **Conclusion**: All of the above factors contribute to the decline in bird populations due to DDT. Therefore, the correct answer to the question is that biomagnification of DDT causes a decline in bird populations by bringing disturbance in calcium metabolism, thinning of the eggs, and premature breaking of the eggs.

**Final Answer**: All of the above.

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