A morphological or physiological character that predisposes an organism to adapt to a changed environment or lifestyle. For example, a hearing mechanism sensitive to low-frequency sound evolved in crickets, perhaps 250 million years ago, to aid intraspecific communication. When bats evolved, only about 50 million years ago, the cricket hearing mechanism served as a preadaptation, being modified to perceive the high-frequency sonar emitted by these night-flying predators, in addition to the low-frequency sounds of other crickets.