Well depending on what the environmental change is the organisms will have to adapt, or move. if they don't they may not survive.
comment if you want an example or 2
<span>Excess nitrogen is brought in the pond from the fertilizer, which are ladden in nitrogen and phosphorous, and rain water or running water takes that nitrogen to the water bodies.Bacteria must have come from the sewage disposal in the pond. Sewage is rich in organic material and allows proliferation of bacteria, which is taken to the pond when the sewage is disposed in the pond.</span><span />
The way that you will easily deduce which one it is is that you'll see the mouth first instead of the anus because of the different ways of development.
