In most natural populations rapid exponential growth is unsustainable. As populations increase, environmental resistance causes the growth rate to slow down, until carrying
capacity is reached. Brainstorm several factors that could be considered as environmental
resistance.

Carrying capacity is defined a the ability of the natural ecosystem to take care of the environment which does not necessarily cause the resistance in population increase.
Explanation:
The earth indeed has a mechanism of delivering changes to the system and keeping it intact but as the case of the rapid growth of population arises the mother nature sees this as an exponent of unsustainable growth as the resource used to sustain large populations is no longer available or are exhausted.
A population increase so does the carrying capacity and workload of the natural environment which at the time gets slow due either due to the man's artificial technology or the natural process like hurricane or earthquake itself.
But seeing the nature as providing possibilities for the existence of the societies throughout ages and hence trying to maintain its originality may break those activities that it considers resistance as several biotic factors like predators, disease, competition, and lack of food.

Where are the phrases

Photosynthesis. . .