The table shows the distribution of traits (A-E) in six extant species (1-6). A "0" indicates the ancestral condition, while "1" indicates the derived condition. Based on this data, which species would be considered the outgroup?

Question

A.  1

B.  2

C.  3

D.  4

E.  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

D.  4

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 To help construct a phylogeny, a trait must have derived characters shared between members of a group, and the ancestral character in the outgroup.
        o An outgroup carries ancestral 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 an outgroup has ancestral characters, the best outgroup here is species 4, which has ancestral characters for all the useful traits (Trait A is shared by everybody and thus not useful).
 
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 species is the outgroup.
        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 outgroup is the species with the most ancestral characters?         o Did you try drawing the cladogram for this data?