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

Question

A.  1 and 3

B.  6 and 4

C.  6 and 5

D.  2 and 3

E.  6 and 3



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

C.  6 and 5

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 must share more synapomorphies than more distantly related pairs of species.
        o So species 6 and 5 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 most closely related species that are highest 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?