The basic requirement for any ecosystem to function and sustain is

Answer

### Step-by-Step Solution:

1. **Understanding Ecosystem**:
- An ecosystem is defined as the interaction between biotic (living organisms) and abiotic (non-living elements like sunlight, water, soil) components along with their environment.

2. **Components of Ecosystem**:
- The biotic components include producers (plants), consumers (animals), and decomposers (fungi, bacteria).
- The abiotic components include sunlight, temperature, water, and nutrients.

3. **Basic Requirement for Ecosystem Functionality**:
- For an ecosystem to function and sustain itself, it requires a constant input of solar energy.

4. **Role of Solar Energy**:
- Solar energy is essential for the process of photosynthesis, where producers (like plants) convert sunlight into chemical energy (food).
- Without solar energy, producers cannot create their own food, which disrupts the entire food chain.

5. **Consequences of Lack of Solar Energy**:
- If producers are unable to produce food, the energy flow to higher trophic levels (consumers) ceases, leading to a collapse of the ecosystem.

6. **Conclusion**:
- Therefore, the basic requirement for any ecosystem to function and sustain is a constant supply of solar energy.