Ecosystem may be defined as:-

Options

A. A localized association of several plants and animals
B. Different communities of plants, animals and microbes together with their physico-chemical environment.
C. Different communities of plants microbes plus their physico-chemical environment
D. None of the above

Answer

**Step-by-Step Solution:**

1. **Understanding the Definition of Ecosystem**: An ecosystem is a complex network that includes all living organisms (plants, animals, and microorganisms) and their interactions with each other and their physical environment.

2. **Components of an Ecosystem**: An ecosystem consists of:
- **Biotic Components**: These are the living organisms, which include:
- **Autotrophs**: Primarily plants that produce their own food.
- **Heterotrophs**: Animals that consume plants and other animals.
- **Microorganisms**: Bacteria, fungi, and other microscopic life forms.
- **Abiotic Components**: These are the non-living elements that affect the ecosystem, such as:
- Soil
- Water
- Air
- Temperature
- Climate

3. **Analyzing the Options**:
- **Option A**: "A localized association of several plants and animals" - This definition is too narrow as it does not include the non-living components.
- **Option B**: "Different communities of plants, animals, and microbes together with their physicochemical environment" - This option includes all living organisms and their interactions with the abiotic environment, making it a comprehensive definition.
- **Option C**: "Different communities of plant microbes plus their physicochemical environment" - This option excludes animals, making it incomplete.
- **Option D**: "None of the above" - This option is incorrect since Option B is a valid definition.

4. **Conclusion**: The correct definition of an ecosystem is provided in **Option B**.

**Final Answer**: Option B - "Different communities of plants, animals, and microbes together with their physicochemical environment."

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