earth is an open ecosystem w.r.t. __(a)__ and is a closed ecosystem w.r.t. __(b)__

Options

A. Energy(a) and heat(b)
B. Food web(a) and energy(b)
C. Energy(a) and nutrient cycle(b)
D. nutrient cycle(a) and energy(b)

Answer

To solve the question "Earth is an open ecosystem w.r.t. __(a)__ and is a closed ecosystem w.r.t. __(b)__", we need to analyze the concepts of open and closed ecosystems.

### Step-by-Step Solution:

1. **Understanding Ecosystems**:
- An ecosystem can be classified as open or closed based on the exchange of energy and matter with its surroundings.

2. **Open Ecosystem**:
- An open ecosystem is one that exchanges both energy and matter with its environment.
- In the case of Earth, it is considered an open ecosystem with respect to **energy**.
- The primary source of energy for Earth is the sun. Solar radiation reaches the Earth, and the Earth, in turn, radiates energy back into space.

3. **Closed Ecosystem**:
- A closed ecosystem, on the other hand, does not exchange matter with its surroundings.
- Earth is considered a closed ecosystem with respect to **matter**.
- The nutrients and materials (such as carbon, nitrogen, and phosphorus) cycle through various forms (like plants, animals, and soil) but do not leave the Earth. They are recycled within the ecosystem.

4. **Conclusion**:
- Therefore, we can fill in the blanks as follows:
- (a) Energy
- (b) Matter (or Nutrient Cycle)

### Final Answer:
Earth is an open ecosystem w.r.t. **energy** and is a closed ecosystem w.r.t. **matter**.