The table shows the distribution of traits (A-E) in six extant species (1-6). A "0" indicates the ancestral condition, while a "1" indicates the derived condition. Based on this data, which pair of species diverged most recently?

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 analyze the information given, using logic, to dissect the problem and determine the answer.
· What key words does the question contain and what do they mean?
        o Traits are features of an organism, used as data to build a tree.
        o Extant species are still alive – i.e., not extinct.
        o The ancestral condition of a trait is the original condition; the derived condition is the more newly evolved version.
 
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 (synapomorphies) 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 Evolutionary distance in a cladogram is indicated by a node defined by a new synapomorphy on one branch.
        o If two species are not differentiated by a character, they must be closely related.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Species 2 and 3 have five shared derived characters. They share more characters than the other species, so they must be most closely related.
 
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 pair of species diverged the most recently.
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that the species with the most shared derived traits are most closely related?