Assertion: Secondary succession always involves a predictable sequence of species and ends up with the same climax community as existed prior to the disturbance.
Reason: A pond cannot be considered as a self. Sustained ecosystem as it does not possess all the structural and functional components which work as a unit in an ecosystem.

Answer

D

Explanation

Secondary succession does not always involve a predictable sequence of species and does not always end up with the same climax community as existed prior to the disturbance. Chance factors may play a role when species not normally a part of the succession happen to colonise, and so alter the normal sequence. Succession will not follow a predictable sequence if the climax community was a relict community that is more appropriate to the new conditions appears after destruction of the relict community. Similarly, where human activities have modified the climate or soil or have eliminated potential colonists by destroying adjacent communitites, the same climax community may not reappear. Pond is a self-sustained ecosystem present in a shallow water body. It has all the structural components (biotic and abiotic) which work as a unit and shwo all the functional aspects of the ecosystem.