Science — CBSE Class 10 board question

(i) Two human-made ecosystems are: aquarium and crop field (agriculture field).

(ii) A pond is a natural, self-sustaining ecosystem with its own decomposers, producers, and consumers maintaining balance. An aquarium is an artificial ecosystem that lacks this balance, so it needs regular cleaning. Cleaning a pond similarly would destroy its natural balance and self-purifying ability.

• For (i), any two valid human-made (artificial) ecosystems are accepted — e.g., aquarium, crop field, garden.
• For (ii), the key idea is that a pond is a natural self-sustaining ecosystem with decomposers and other organisms that naturally break down waste, whereas an aquarium is artificial and lacks this balance. Examiners expect the term "self-sustaining" or equivalent reasoning about natural balance being disturbed.
• Note: The source passages provided do not directly cover this topic, but this answer is based on the standard CBSE Class 10 Science Chapter 15 (Our Environment) content.