Based on the below diagram and other information from your text, what is the most likely (e.g., most parsimonious) explanation for the evolution of flight in vertebrates?

Question

A.  The common ancestor of all terrestrial vertebrates was wingless and wings evolved independently three different times: in bats, in pterosaurs and in the common ancestor of birds and dinosaurs.

B.  Wings evolved once in vertebrates (e.g., the common ancestor of all terrestrial vertebrates had wings) and wings were subsequently lost in all but three lineages: bats, pterosaurs and birds.

C.  The common ancestor of all terrestrial vertebrates was wingless and wings evolved independently three different times: in bats, in pterosaurs and in birds.

D.  The common ancestor of all terrestrial vertebrates was wingless and wings evolved independently two different times: once in bats and once in the common ancestor of birds, pterosaurs and dinosaurs.

E.  The common ancestor of all terrestrial vertebrates was wingless and wings evolved independently three different times: in bats, in birds and in the common ancestor of pterosaurs and dinosaurs.



Clarify Question

· What is the key concept addressed by the question?

· What type of thinking is required?



Gather Content

· What do you know about the evolution of flight in vertebrates? What other information is related to the question?



Choose Answer · Given what you now know, what information is most likely to produce the correct answer?



Reflect on Process

· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  The common ancestor of all terrestrial vertebrates was wingless and wings evolved independently three different times: in bats, in pterosaurs and in birds.

Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the evolution of flight in vertebrates.
· What type of thinking is required?
        o You are being asked to evaluate statements about the evolution of flight in vertebrates.

Gather Content
· What do you know about the evolution of flight in vertebrates? What other information is related to the question?
        o The evolution of flight is a classic example of convergent evoluØtion, having occurred independently four times, once in insects and three times among vertebrates. All three vertebrate fliers modified the forelimb into a wing structure, but they did so in different ways, illustrating how natural selection can sometimes build similar structures through different evolutionary pathways. Based on the evolutionary tree, you can see that the vertebrates with and without wings are mixed, showing that the common ancestor to vertebrates did not have wings, and that wings arose three different times in bats, in pterosaurs and in birds.

Choose Answer · Given what you now know, what information is most likely to produce the correct answer?
        o The common ancestor of all terrestrial vertebrates was wingless and wings evolved independently three different times: in bats, in pterosaurs and in birds. If the common ancestor to dinosaurs and either pterosaurs or birds had wings which were lost in dinosaurs, then the fossils of those species would have evidence of wings. This has not been seen.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to evaluate statements about the evolution of flight in vertebrates. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you think that the common ancestor to dinosaurs and either pterosaurs or birds had wings and then it was lost in dinosaurs? Did you think that the common ancestor to all vertebrates had wings?