Birds, snakes, lizards, turtles, and crocodiles are all thought to share a common ancestor and several homologous traits. Assuming that this is true, these groups of animals and their common ancestor would represent

Question

A.  a polyphyletic group.
B.  a monophyletic group.
C.  homoplastic convergence.
D.  an outgroup.
E.  a species cluster.


Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?
 
Gather Content
· What do you already know about monophyly?
 
Consider Possibilities · Consider the different answer options. Which can you rule out?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach 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

B.  a monophyletic group.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses monophyly.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.
· What key words does the question contain and what do they mean?
        o The common ancestor of a group is the last organism that gave rise to all the members of the group – i.e., the organism at the bottom node on the tree of the group.
        o Homologous traits are traits in different species that are the same, or very similar, because they arose from a common evolutionary origin.
 
Gather Content
· What do you already know about monophyly?
        o A monophyletic group is a group that includes the most recent common ancestor of the group and all of its descendants.
 
Consider Possibilities · Consider the different answer options. Which can you rule out?
        o Could you call this group of organisms and their ancestor a polyphyletic group? No, because that is a grouping that lacks the ancestor.
        o Could you call this group of organisms and their ancestor a homoplastic convergence? No, that would imply that all the shared characters were due to coincidence, not due to common evolutionary origin.
        o Could you call this group of organisms and their ancestor an outgroup? No, because that would be a distantly related species or group, relative to some other group of organisms being discussed.
        o Could you call this group of organisms and their ancestor a species cluster? No, that is not the proper term.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Could you call this group of organisms a monophyletic group? Yes. A monophyletic group includes the most recent common ancestor of the group and all of its descendants.

  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 how you could describe the group including birds, snakes, lizards, turtles, and crocodiles, plus their ancestor.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that the group of organisms sharing traits, and including the common ancestor, constitutes a monophyletic group.