The table shows the distribution of traits (A-E) in six extant species (1-6). A "0" indicates the ancestral condition, and a "1" indicates the derived condition. Which trait is least informative of phylogenetic relationships within the group?
A. A
B. B
C. C
D. D
E. E
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?
E. E
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.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Since trait E is the same (derived) in all the species listed here, that trait cannot help us to understand their relationships.
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 of the traits is least useful for understanding the phylogenetic relationships.
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 a trait is only useful for building a cladogram if the trait varies (from ancestral to derived) in different species?
o Did you try drawing the cladogram for this data?
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