The Four ‘F’s of Biology are…

… Feeding, Fighting, Fleeing and… Reproduction.

References

Jean-Marc Fellous and Michael A. Arbib (2005). Who Needs Emotions? The Brain Meets the Robot. See page 355: “Karl Pribram (1960) has quipped that the limbic system is responsible for the ‘four Fs:’ Feeding, Fighting, Fleeing, and Reproduction”.

Pribram, Karl H. (1960). A review of theory in physiological psychology. Annual Review of Psychology, 11, 1-40. See pages 11 and 13.