Correct answer: (1) A stable ecosystem can be altered, and then it can recover to a point of stability.
The graph illustrates an ecosystem that has been disturbed. This has caused a decline in the population of species. After some time, another community starts to inhabit the ecosystem and starts to grow in numbers, until it reaches the climax community, which is the most stable stage of the ecosystem.
(2) An ecosystem remains unchanged.
If the ecosystem remains unchanged, then the stability curve must be drawn as a strait horizontal line.
(3) The stability of an ecosystem remains unchanged but its biodiversity decreases.
Ecosystem stability depends on the biodiversity or number of species found in the ecosystem. Thus, once biodiversity decreases, ecosystem stability is also changed.
(4) A stable ecosystem cannot recover after it is altered.
An ecosystem has a natural way of recovering from any disturbance to continue life. This phenomenon is called ecological succession. Natural changes and species replacements occur in an ecosystem over time.