Identify the statements which are not true for the natural ecosystem.

(A) Grassland and desert are examples of terrestrial ecosystem.

(B) Oceans and rivers are man-made ecosystems.

(C) Wetland and estuary are examples of aquatic ecosystem.

(D) Crop fields and aquarium are natural ecosystems.

Choose the correct answer from the options given below:

(B) and (D) only

The correct answer is Option (4) –(B) and (D) only

(A) Grassland and desert are examples of terrestrial ecosystem.

• This statement is true. Terrestrial ecosystems refer to land-based ecosystems, and grasslands and deserts are examples of such ecosystems.

(B) Oceans and rivers are man-made ecosystems.

• This statement is not true. Oceans and rivers are natural ecosystems that exist without significant human intervention. They are vast bodies of water that support diverse forms of life and are shaped by natural processes such as currents, tides, and geological forces.

(C) Wetland and estuary are examples of aquatic ecosystem.

• This statement is true. Aquatic ecosystems refer to water-based ecosystems, and wetlands and estuaries are examples of such ecosystems. Wetlands are areas where water covers the soil or is present either at or near the surface of the soil all year or for varying periods of time during the year, while estuaries are areas where freshwater from rivers and streams meets and mixes with saltwater from the ocean.

(D) Crop fields and aquarium are natural ecosystems.

• This statement is not true. Crop fields are areas where crops are cultivated, and aquariums are artificial environments where aquatic organisms are kept for display or research purposes. These are examples of human-made or artificial ecosystems rather than natural ecosystems, as they are heavily influenced by human activities and are not representative of naturally occurring ecological systems.

So, options (B) and (D) are not true for natural ecosystems.