Which of the following is correct regarding the ecosystem?
(a) There is cyclic exchange of materials between living beings and environment.
(b) The flow of energy is unidirectional
(c) It is a self-regulating unit
(d) All of these

Options

A. There is cyclic exchange of materials between living beings and environment.
B. The flow of energy is unidirectional
C. It is a self-regulating unit
D. All of these

Answer

To solve the question regarding the ecosystem, we need to analyze each of the provided statements and determine their correctness.

1. **Statement (a): There is cyclic exchange of materials between living beings and environment.**
- In an ecosystem, materials such as nutrients and water are recycled between living organisms (biotic components) and their environment (abiotic components). This cyclic exchange is crucial for maintaining the balance of ecosystems. Therefore, this statement is **correct**.

2. **Statement (b): The flow of energy is unidirectional.**
- Energy in an ecosystem flows in a unidirectional manner. It starts from the sun, is captured by producers (like plants), and then moves through various trophic levels (herbivores to carnivores). Once energy is used, it is not recycled back to the producers, making this statement **correct**.

3. **Statement (c): It is a self-regulating unit.**
- Ecosystems are indeed self-regulating systems. They can maintain stability through feedback mechanisms, where the interactions between biotic and abiotic components help regulate population sizes and resource availability. Thus, this statement is also **correct**.

4. **Statement (d): All of these.**
- Since statements (a), (b), and (c) are all correct, statement (d) which claims that "all of these" statements are correct is also **correct**.

Based on the analysis, the correct answer is:
**(d) All of these.**