CEVAP:

While hunger and thirst are essential for the survival of an organism, sexuality is important only for the continuation of a species. When hunger and thirst drives are not satisfied for a long time, the organism may die. However, this is not the case for sexuality behavior. In addition, the number of stimulants that might trigger sexuality motive is quite high. While hunger and thirst are directly affected by stimulants related with these needs, anything might be a stimulant for sexuality. In addition, organism spends energy while satisfying sex motive, but satisfaction of hunger or thirst provides energy for the body. Also, the motive of hunger or thirst increases even if the individual does not want. In sexuality, the individual wishes and starts the arousal and later searches for ways to relieve this tension.