Word Study
biological clock
THESAURUS
biological clock
anima, animating force, atman, bathmism, beating heart, biorhythm, blood, breath, breath of life, divine breath, divine spark, elan vital, essence of life, force of life, growth force, heart, heartbeat, heartblood, impulse of life, inspiriting force, jiva, jivatma, life breath, life cycle, life essence, life force, life principle, life process, lifeblood, living force, pneuma, prana, seat of life, soul, spark of life, spirit, vis vitae, vis vitalis, vital energy, vital flame, vital fluid, vital force, vital principle, vital spark, vital spiritFor further exploring for "biological clock" in Webster Dictionary Online