Answer:
Even a slight reproductive advantage will eventually lead to the elimination of the less well adapted of two competing species
Explanation:
The competitive exclusion describes relationship between two species that compete for the limiting sources, and cannot coexist. It is enough for one species to have slightly advantage to be dominant over the other. As a consequence, other species (the weaker one) will be extincted (shift to a different ecological niche).
An example of secondary pollutant is sulfurage
One of the many changes are the seasons, ex Winter, Spring, Summer, Fall