List two natural ecosystems.

Explanation

### Step-by-Step Solution:

1. **Define Ecosystem**: An ecosystem is a community of living organisms (plants, animals, microorganisms) interacting with their physical environment (soil, water, air) in a specific area. It includes both biotic (living) and abiotic (non-living) components.

2. **Identify Types of Ecosystems**: Ecosystems can be broadly classified into two main categories:
- **Terrestrial Ecosystems**: These are land-based ecosystems. Examples include forests, grasslands, deserts, and tundras.
- **Aquatic Ecosystems**: These are water-based ecosystems. They can be further divided into freshwater ecosystems (like rivers and lakes) and marine ecosystems (like oceans and coral reefs).

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