In: Biology
Some species of finches have more robust beaks in order to crush seeds available in their environment. Recent data show that their BMP4 expression in the developing beak is initiated sooner than other species, resulting in more tissue growth during embryogenesis.
First, indicate whether this is an example of heterotopy, heterochrony, heterometry, or heterotypy, defining your chosen term. Second, describe how you might use the chicken embryo as a model system to test the hypothesis that this earlier timing of BMP4 expression is responsible for more robust beaks in some species of finches. Be sure to provide a brief description of the relevant technique(s), and to include at least one control.