Ecological niche is

Options

A. the sum total of environmental factors or conditions , which determine the existence of organism , population , or community in a particular locality
B. an ecologically adapted zone and is the address of an organism
C. the physical position and functional role of a species within the community
D. formed of all plants and animals living at the bottom of a lake

Answer

To determine the correct definition of an ecological niche from the provided options, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Ecological Niche**:
- An ecological niche refers to how an organism or species interacts with its environment, including its habitat, resource use, and role in the ecosystem.

2. **Analyze the Given Options**:
- **Option 1**: "The sum total of environmental factor or condition which determines the existence of organism, population or community in a particular locality."
- This describes environmental conditions but does not specifically define the niche.
- **Option 2**: "An ecologically adapted zone and is the address of an organism."
- This suggests a location but lacks the functional aspect of a niche.
- **Option 3**: "The physical position and the functional role of species within the community."
- This option captures both the physical location and the role of the species, aligning well with the definition of an ecological niche.
- **Option 4**: "Formed of all plants and animals living at the bottom of the lake."
- This describes a specific habitat, not the concept of a niche.

3. **Select the Correct Option**:
- Based on the analysis, **Option 3** is the most accurate definition of an ecological niche as it encompasses both the physical position and the functional role of a species within its community.

4. **Conclusion**:
- Therefore, the correct answer is **Option 3**: "The physical position and the functional role of species within the community."