The two figures to the left show two potential phylogenies of a group of birds c
ID: 78007 • Letter: T
Question
The two figures to the left show two potential phylogenies of a group of birds called the ratites. These birds, with the exception of tinamous, are all flightless and occur on the continents that were formerly part of the southern supercontinent of Gondwana. Their content of Elephant bird occurrence (or former occurrence, Moas and the Elephant bird are extinct) is listed after their name in phylogeny C. We know that Africa split apart from the rest of the landmass first, followed by New Zealand. Finally, Australia and Elephant South America broke apart. One of these bird phylogenies reflects the biogeographic explanation of the breakup of Gondwana, while the other is based on morphological homologies Which phylogeny, B or C, would be expected if the evolutionary relationships among these birds reflected the biogeographic pattern of the breakup of Gondwana. Explain your answer. If the phylogeny you did NOT choose in A is correct, how could you explain the geographic ranges of these species? Based on what you know about trait evolution, would you expect it to be easier for flightlessness to evolve from flying species or for flight to evolve from a flightless species? Why? How would flying change the likelihood of dispersal between separate continents? How might your answers from parts c and d help clarify which of the two phylogenies is more likely?Explanation / Answer
a.
b.
c.
d.
e.
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