<span>The deposition of heavy sediment can significantly diminish the water quality and aquatic habitat. The sentiment in the water can reduce the sunlight that reaches the floor of the waterway, affecting animal and plant life. For example, photosynthesis may be less effective due to the decreased sunlight and the gills of fish may get clogged from the sediment.</span>
It should be natural selection since there is no external influence implied. (like environment or genetic mutations.)
Deforestation. The animals forest that they once lived in are bein cut down.
