The correct option is 1 and 2 only.
Explanation
An ecosystem is a functional unit of nature where living organisms interact among themselves and with the surrounding physical environment. Ecosystems are broadly classified based on their origin into Natural Ecosystems (self-regulating) and Artificial Ecosystems (man-made). Based on habitat, they are categorized into Terrestrial (land-based) and Aquatic (water-based).
Statement-wise Analysis:
- Pair 1 is correctly matched: Forests are land-based environments where the interaction of flora and fauna occurs on solid ground. Thus, they are classified as Terrestrial ecosystems, similar to grasslands and deserts.
- Pair 2 is correctly matched: An estuary is a semi-enclosed coastal body of water where freshwater from rivers mixes with saltwater from the ocean. As the primary medium is water, it is an Aquatic ecosystem.
- Pair 3 is incorrectly matched: An aquarium is created and maintained by humans. It lacks the complete self-regulating capabilities of a wild environment and depends on human intervention for food supply and waste management. Therefore, it is an Artificial (Anthropogenic) ecosystem, not a natural one.
- Pair 4 is incorrectly matched: The Biosphere is the narrow zone of Earth where land, water, and air interact to support life. It represents the sum of all ecosystems on Earth. Consequently, it is regarded as a Global ecosystem, not a local one.
Key Takeaway:
Natural ecosystems (e.g., forests, estuaries, ponds) evolve naturally, whereas artificial ecosystems (e.g., aquariums, crop fields, gardens) are engineered by humans. The Biosphere is the composite global ecosystem.