These are clearly different alterations, brought about by different mechanisms, with different effects. Eg, especially with fossil record there is no developmental information. But need not result from heterochronic alterations of developmental processes. Discuss general problem in evol biol of the nonlinearity of genotype-phenotype mapping. Can't predict type or magnitude of one change from knowledge of the other.
Mapping is done by the complex phenomenon of development.
A. Differentiative heterochronies can potentially have drastic effects on morphology by altering basic organization of embryo, patterns of morphogenesis, or differentiation. It is this kind of heterochrony that is seen as central to large-scale yet integrated changes in morphology by means of developmental alterations. Can occur by differences in response to growth hormones by different target tissues. 14 mutant causes cell line to undergo more mitotic divisions before differentiation. Thus delayed onset of differentiaton.