How many of the following statements are correct?
A. An ecosystem varies greatly in size, from a small pond to a large forest or a sea.
B. Many ecologists regard the entire biosphere as a global ecosystem, a composite of all local ecosystems on Earth.
C. Pond, lake, wetland, river and estuary are some examples of aquatic ecosystems.
D. Crop fields and an aquarium may be considered as natural ecosystems.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Three
An ecosystem is a functional unit of nature in which living organisms interact among themselves and with their physical surroundings. NCERT groups ecosystems as terrestrial and aquatic, and also separates natural ones from those made by humans.
A. An ecosystem varies greatly in size, from a small pond to a large forest or a sea. — True. There is no fixed size; a pond and a sea are both ecosystems.
B. Many ecologists regard the entire biosphere as a global ecosystem, a composite of all local ecosystems on Earth. — True. The biosphere is the largest ecosystem, made up of all the smaller ones.
C. Pond, lake, wetland, river and estuary are some examples of aquatic ecosystems. — True. All of these are water-based, while forest, grassland and desert are the terrestrial examples.
D. Crop fields and an aquarium may be considered as natural ecosystems. — False. Crop fields and an aquarium are set up and kept by humans, so NCERT calls them man-made ecosystems.
A, B and C are correct, so three statements are correct.
NCERT Extract:
Ecosystem – “… Ecosystem varies greatly in size from a small pond to a large forest or a sea. Many ecologists regard the entire biosphere as a global ecosystem, as a composite of all local ecosystems on Earth. Since this system is too much big and complex to be studied at one time, it is convenient to divide it into two basic categories, namely terrestrial and aquatic. Forest, grassland and desert are some examples of terrestrial ecosystems; pond, lake, wetland, river and estuary are some examples of aquatic ecosystems. Crop fields and an aquarium may also be considered as man-made ecosystems.”