Evidence suggests that the crocodiles are more closely related to the birds than the turtles and snakes. If so, then including crocodiles, but not birds, in the Class Reptilia would make the Class Reptilia

Question

A.  a monophyletic group.
B.  a paraphyletic group.
C.  a polyphyletic group.
D.  parsimonious.
E.  not homologous.


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 paraphyletic 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 Class Reptilia is a traditional grouping of reptiles, but recent understanding has revealed that the grouping is not monophyletic, since birds should be included.
 
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 In this case, would Class Reptilia be a monophyletic group? No, because a monophyletic group includes all the related members within the group.
        o In this case, would Class Reptilia be a polyphyletic group? No, that would be a grouping of distant relatives, missing the common ancestor (such as bats and birds).
        o In this case, would Class Reptilia be parsimonious? No. Something is only parsimonious if it describes the simplest, most likely evolutionary scenario.
        o In this case, would Class Reptilia not be homologous? No, this is not the correct way to describe it. Only features can be homologous, if they are derived from a common evolutionary origin.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o In this case, would Class Reptilia be a paraphyletic group? Yes, that is the correct term for a group that is missing one of its members.
  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 describe “Class Reptilia” defined without the inclusion of birds.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that when a member is missing from a grouping, that grouping is called paraphyletic?