Biology Reference
In-Depth Information
FIGURE 11.5
The direc-
tions of ontogenetic change of
the cotton rat skull measured
between successive ages
(in
days postnatal).
link between ontogeny and extrinsic time, as in studies that relate evolving ontogenies to
ecology. That requirement for age data may be most obvious for the case of heterochrony,
which concerns the changes in developmental rate and timing that produce the parallelism
between ontogeny and phylogeny (
Gould, 1977
). Without age data, it is not possible to
distinguish between various changes that produce the same morphological outcome, such
as a later onset of development, a slower rate of development or a shorter duration of
development. All produce a descendant that resembles the ancestral juvenile. In another
case, we also need information about age because the questions are specifically
