You are given three cladograms that represent possible evolutionary relationship
ID: 189876 • Letter: Y
Question
You are given three cladograms that represent possible evolutionary relationships for 3 taxa identified as 1, 2 and 3. Consider three characters, the number of toes on the front foot, skin covering and tail: with the ancestral character-state having 5 toes, scaly skin and a tail. If each taxon had the following characters:
Taxon
Characters
1
5 toes
scales
no tail
2
4 toes
scales
no tail
3
5 toes
no scales
tail
Which cladogram represents the most parsimonious phylogeny? ______
Briefly state WHY?
Taxon
Characters
1
5 toes
scales
no tail
2
4 toes
scales
no tail
3
5 toes
no scales
tail
2 3 Scales no scales Tail no tall Tall- no tail 5 toes 4 toesExplanation / Answer
The parsimonious phylogeny is the evolutionary relationship that requires the fewest number of changes. Three changes were needed to produce the derived character states:
In Taxon 1 + taxon 2 evolution, the tail is lost. Scales are lost in evolution of taxon 3. In the evolution of taxon 2, a toe is lost.
In claudogram A and C, the tail was lost was regained and then lost again.
The claudogram B is the most plausible claudogram as least number of extreme changes occurred in the taxons. It provides the simplest explanation of the evolutionary changes between the 3 taxons. In this claudogram, once the tail is lost, it is not regained. They first lost the scales, then lost the tail and finally the toes. Hence, this claudogram had the least number of changes.
Right Option: Claudogram B represents the most parsimonious phylogeny.
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