The largest man-made ecosystem lackes all,except

Options

A. High diversity
B. High productivity
C. Complex food chains
D. Frequent circulation of nutrients

Answer

To solve the question regarding the largest man-made ecosystem and what it lacks, we need to analyze the options provided: high diversity, high productivity, complex food chain, and frequent circulation of nutrients.

### Step-by-Step Solution:

1. **Understanding Man-Made Ecosystems**:
- Man-made ecosystems are environments that have been created or significantly altered by human activity. Examples include zoos, aquariums, and agricultural fields.

2. **Evaluating High Diversity**:
- In a zoo, for instance, while there are various animal species, the overall number of species is limited compared to a natural ecosystem. Thus, the diversity is not high.
- **Conclusion**: Man-made ecosystems typically lack high diversity.

3. **Evaluating High Productivity**:
- Productivity refers to the rate at which energy is produced in an ecosystem. Man-made ecosystems can be designed to be productive, especially in controlled environments like farms or aquariums.
- **Conclusion**: Man-made ecosystems can exhibit high productivity.

4. **Evaluating Complex Food Chains**:
- A complex food chain involves multiple species interacting in various ways. In a zoo, different species can interact, forming food chains and webs.
- **Conclusion**: Man-made ecosystems can have complex food chains.

5. **Evaluating Frequent Circulation of Nutrients**:
- Nutrient cycling is essential for ecosystem health. In man-made ecosystems, especially those designed for specific purposes, nutrient cycling can occur, though it may not be as dynamic as in natural ecosystems.
- **Conclusion**: Man-made ecosystems can have frequent circulation of nutrients.

6. **Final Analysis**:
- Based on the evaluations, the only option that man-made ecosystems lack is **high diversity**. Therefore, the correct answer to the question is **high diversity**.

### Final Answer:
The largest man-made ecosystem lacks all, except **high productivity, complex food chain, and frequent circulation of nutrients**. It specifically lacks **high diversity**.