embryology
milhayser | September 5, 2012On Pharyngula, PZ Myers considers a computer model which posits that bones are simply exoskeletons turned inside-out. Myers writes “We know from the homology of the patterning molecules involved that vertebrates and invertebrates are upside-down relative to each other, so at some point an ancestor flipped.” Such major differences in body plan arise during embryonic development, driven by highly evolved genetic instruction. But the growth of internal and external skeletons depends on distinct biological mechanisms, leading PZ to call the dataless computer model “abiological and ahistorical…
jwhitfield | February 9, 2009From the first dawn of life, all organic beings are found to resemble each other in descending degrees, so that they can be classed in groups under groups.
Isn't that a good sentence? It's the first of this chapter. There's music in the way the Biblical ring of "From the first dawn of life", falls towards the swallowed repetition of "groups under groups", which itself mirrors and explains the descending degrees of resemblance that gives the sentence its scientific filling.
The next line is just as good: "This classification is evidently not arbitrary like the grouping of the stars in…