Consider the cladogram shown. Which pair of species shares the greatest number of derived characters (synapomorphies)?

Question

A.  1 and 4

B.  2 and 3

C.  2 and 4

D.  6 and 4

E.  6 and 5





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 cladistics?

 

Consider Possibilities

· What other information is related to the question? Which information is most useful?

 

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.  2 and 3


Clarify Question
· What is the key concept addressed by the question?
        o This question addresses cladistics.
· 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 A cladogram is a diagrammatic representation of a hypothesis about evolutionary relationships.
        o A synapomorphy is a shared derived character. In other words, a newly-evolved trait shared by a group of species.
 
Gather Content
· What do you already know about cladistics?
        o Cladistics is the method used to construct a cladogram — a graphically represented hypothesis of evolutionary relationships.
        o Only shared derived characters are useful for inferring phylogenies, and they must be contrasted to an outgroup that has the ancestral characters.
 
Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o A cladogram is a set of nested clades, characterized by their synapomorphies (shared, derived characters).
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Since the nested clades are defined by synapomorphies, the species in the innermost nested clade – the most closely related species in this cladogram – must share more synapomorphies than more distantly related pairs of species.
        o So species 2 and 3 share the most characters.
 
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 which two species share the most derived characters.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that a large number of shared characters indicates that two species are closely related? So the two species closest on the tree have the most shared derived characters.
        o Did you remember that nodes are established by the appearance of a new derived character on one branch?