Literally ‘different place’: a mechanism for generating changes in developmental outcomes that depends on where certain genes are expressed. For example, in the developing hindlimb of a chick the webbing between the toes is lost because of the action of a signal protein called bone morphogenetic protein 4 (BMP4), which stimulates cell death (apoptosis) of those tissues. By contrast, in the hindlimb of a duck a second protein called Gremlin is also expressed in the webbing cells; this inhibits the action of BMP4, thus preventing apoptosis and resulting in a webbed foot. Changes in the regulatory regions of such genes can alter in which tissues they are expressed, leading to morphological changes that may be of adaptive significance. Compare heterochrony; heterometry; heterotypy.