Question

Evolution ; Phylogeny ; Cladistics ;

In a clade of turtles, shell color is either light or dark. The phylogeny of this clade is printed below, along with a number to label each species and drawings to show which species have light or dark shells. In your research, you have discovered a procedure that can reveal whether shell color is homologous between species 2 and another species. This procedure is time-consuming and expensive, however, because it requires detailed study of a turtle's shell pigmentation. It has therefore been conducted on only two other species so far, with the following results: .Dark shell color is homologous in species 2 and species 5 4 .Dark shell color is analogous in species 2 and species 6 a.) Based only on the information so far, where in the historv of this clade is it established that shell color was dark? Draw your answer on the branches of the phylogeny above (an example is shown on the right). Also explain briefly. 9 10 12 b.) You have received enough new funding to conduct your shell pigmentation procedure on one more species, to test homology with species 2. If your goal is to establish whether the MRCA of all twelve species had a dark shell, which species would you choose? Explain briefly. The renaining parts use ‘species X, to mean the species you chose as your answer in part b c.) If you find that dark shell color is homologous in species 2 and species X, what would you conclude about the shell color of the MRCA of this clade of twelve turtles? Explain briefly. d.) If you find that dark shell color is analogous in species 2 and species X, what would you conclude about the shell color of the MRCA of this clade of twelve turtles? Explain briefly.

Answer 1

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