A(n) is anything that causes an increase in the frequency of a behavior.

Behavior-altering effect- either (a) an increase in the current frequency of behavior that has been reinforced by some stimulus, object, or event, called an evocative effect; or (b) a decrease in the current frequency of behavior that has been reinforced by some stimulus, object, or event, called an abative effect.

Explanation:

Photosynthesis occurs in the chloroplasts, whereas cellular respiration occurs in the mitochondria.