Intraspecific allometry just describes growth

Intraspecific allometry just describes growth - . Figures...

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Intraspecific allometry just describes growth, and alone is not an evolutionary comparison. It is of interest that the allometric coefficient of Bio 48 males and females is ~ 1.0, but if the toddler data are included the allometric coefficient goes up to ~ 1.3. This means that as adults we have about the same proportions (a=1) but as we grow from infant to adult, our arms get proportionally longer (a=1.3). Allometry is useful in describing the evolution of size and shape. Different species attain different morphologies by virtue of different timing of various developmental processes. This change in timing is called heterochrony
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Unformatted text preview: . Figures 21.5 - 21.8 and table 21.1, pgs. 590-594 review some of the typical examples of heterochrony. Using the figure below, we can group these into two general classes: in figs B and C the ancestor (dotted) and descendant (solid, but hard to see in C) have the same slope but the descendant stops growing (=adult) at a different time ; in figure D and E, the descendant grows for the same amount of time (in these cases same amount of x but different amount of y) but at a different slope . Both are heterochronic changes because some aspect of timing (relative or absolute) has changed in evolution....
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