Why is a lake considered to be a natural ecosystem?

Explanation

### Step-by-Step Text Solution:

1. **Definition of Natural Ecosystem**: A natural ecosystem is defined as a self-sustaining system where the growth and survival of organisms depend entirely on natural processes.

2. **Characteristics of a Lake**: A lake is considered a natural ecosystem because it hosts a variety of organisms, including different species of fish, microbes, and plankton.

3. **Self-Sustaining Nature**: The organisms in a lake are self-sustaining. They produce their own food using natural resources such as sunlight, wind, and climatic changes.

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