Study of inter-relationships between organisms and their environment is

Options

A. Ecology
B. Ecosystem
C. Phytogeography
D. Ethology

Answer

To solve the question regarding the study of inter-relationships between organisms and their environment, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Key Concepts**: The question asks about the study of inter-relationships between organisms and their environment. This indicates a focus on interactions among living organisms and their surroundings.

2. **Evaluate the Options**: The options given are:
- Ecology
- Ecosystem
- Phytogeography
- Ethology

3. **Define Each Term**:
- **Ecology**: This is the branch of biology that deals with the relationships of organisms to one another and to their physical surroundings. It encompasses the study of interactions between organisms and their environment.
- **Ecosystem**: This refers to a community of living organisms (plants, animals, and microbes) interacting with one another and with their non-living environment (like air, water, and minerals). It is a broader concept that includes ecological interactions but is not solely focused on the study of those interactions.
- **Phytogeography**: This is a branch of botany that focuses on the geographical distribution of plants. It does not encompass the broader interactions between all organisms and their environment.
- **Ethology**: This is the scientific study of animal behavior, particularly in natural environments. It does not cover the interactions between all types of organisms and their environments.

4. **Select the Correct Answer**: Based on the definitions, the term that best fits the description of studying inter-relationships between organisms and their environment is **Ecology**.

5. **Conclusion**: Therefore, the correct answer to the question is **Ecology**.

### Final Answer:
The study of inter-relationships between organisms and their environment is called **Ecology**.