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How can morphological data accurately represent evolution?

  1. Dec 23, 2015 #1
    I was reading through the answer key of question 3 in an AP Biology free response (found here: https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap15_biology_sg.pdf ), and it had this question:

    "Identify whether morphological data or amino acid sequence data are more likely to accurately represent the true evolutionary relationships among the species, and provide reasoning for your answer."

    My natural response is that amino acid sequence is more accurate, however, Collegeboard also acknowledged "morphological data" as a valid response. I read Collegeboard's reasoning (posted below), and I do not understand it. Can anyone understand their reasoning (see below)?

    " Morphological data reasoning:
    • Similar molecular sequences may result in different morphologies.

    • An example of species with similar proteins but different morphology (e.g., chimps and

      humans). "
  2. jcsd
  3. Dec 23, 2015 #2


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    In the days before modern molecular biology and DNA sequencing, biologists inferred evolutionary relationships solely from morphological data and created a mostly correct picture. Amino acid (and DNA) sequences often give better results because they provide more data from which to infer evolutionary relationships. Of course, there are some limitations to using molecular data. For example, many morphological changes can be due to changes in non-coding DNA sequences (e.g. enhancer sequences), many of which are not known or well understood, so morphological data can be complementary to molecular data. The best models will use some combination of the two, though figuring out the right statistical models to weight the strengths and weaknesses of the two types of data is not an easy task.
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