Consider the following statements conerning food chains
(i) Removal of 80% tigers from an area resulted in greatly increased growth of vegetation
(ii) Removal of most of the carnivores resulted in an increased population of deers
(iii) The length of food chains is generally limited to 3 - 4 trophic levels due to energy loss
(iv) The length of food chains may vary from 2 to 8 trophic levels
Which two of the above statements are correct?

Options

A. II and III
B. III and IV
C. I and IV
D. I and III

Answer

To solve the question, we need to evaluate each of the four statements concerning food chains and determine which two are correct.

### Step-by-Step Solution:

1. **Evaluate Statement (i)**: "Removal of 80% tigers from an area resulted in greatly increased growth of vegetation."
- In a food chain, tigers (as apex predators) help control the population of herbivores (like deer). If 80% of tigers are removed, the deer population would likely increase due to reduced predation. This increased deer population would lead to overgrazing, which would actually decrease vegetation, not increase it.
- **Conclusion**: This statement is **incorrect**.

2. **Evaluate Statement (ii)**: "Removal of most of the carnivores resulted in an increased population of deers."
- Carnivores, such as tigers, keep herbivore populations in check. If most carnivores are removed, the herbivore population (deers) would increase due to the lack of predation.
- **Conclusion**: This statement is **correct**.

3. **Evaluate Statement (iii)**: "The length of food chains is generally limited to 3 - 4 trophic levels due to energy loss."
- According to the 10% rule of energy transfer in ecosystems, only about 10% of energy is passed from one trophic level to the next. This significant energy loss limits the number of trophic levels in a food chain, typically to 3 or 4 levels.
- **Conclusion**: This statement is **correct**.

4. **Evaluate Statement (iv)**: "The length of food chains may vary from 2 to 8 trophic levels."
- While food chains can theoretically have varying lengths, having 8 trophic levels is impractical due to the energy loss mentioned earlier. Generally, food chains are observed to have 3 to 4 levels for sustainability.
- **Conclusion**: This statement is **incorrect**.

### Final Conclusion:
The two correct statements are:
- Statement (ii): Removal of most of the carnivores resulted in an increased population of deers.
- Statement (iii): The length of food chains is generally limited to 3 - 4 trophic levels due to energy loss.

Thus, the correct answer is **option 1** (statements ii and iii are correct).