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, we need to identify the correct terms for the blanks in the statement: "Earth is an open ecosystem w.r.t. __(a)__ and is a closed ecosystem w.r.t. __(b)__."

### Step-by-Step Solution:

1. **Understanding Open Ecosystem**:
- An open ecosystem allows the exchange of energy with its surroundings. In the context of Earth, this refers to the flow of energy from the sun through various trophic levels (producers, consumers, etc.).
- **Hint**: Think about what enters and exits an ecosystem in terms of energy.

2. **Identifying (a)**:
- Since Earth receives energy from the sun and this energy flows through different levels of the food chain, we can conclude that Earth is an open ecosystem with respect to **energy**.
- **Hint**: Consider what is constantly being supplied to the Earth from an external source.

3. **Understanding Closed Ecosystem**:
- A closed ecosystem does not allow the exchange of materials with its surroundings. Instead, materials (like nutrients) cycle within the ecosystem.
- **Hint**: Think about what remains within the ecosystem and is recycled.

4. **Identifying (b)**:
- In the context of Earth, nutrients (such as carbon, nitrogen, and phosphorus) are recycled and do not leave the ecosystem once they enter. Therefore, Earth is a closed ecosystem with respect to **nutrients**.
- **Hint**: Reflect on the concept of nutrient cycles and how they function in an ecosystem.

### Final Answer:
- Earth is an open ecosystem w.r.t. **(a) energy** and is a closed ecosystem w.r.t. **(b) nutrients**.