Q:Process:  - Pollution enters natural water sources such as rivers and lakes - The pollution negatively affects the water quality - The pollution negatively affects the health of plants and animals - The plants and animals have shorter, less healthy lives - The plants and animals do not reproduce very well - The number of plants and animals decreases over time - The quality of water gets worse and worse as there are no plants or animals to clean it - Eventually there is nothing living in the water and it is unusable -   Perturbation hypothesis: suppose the population decreases happens, how will it affect there are more pollution producing companies.  Does the supposed perturbation have an effect (direct or indirect) on the process?
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