Question

need help with B, C, D

* 4. At right are 5 species of starfish, and where they're found. (18 pts) P Q R S T a. Draw a phylogeny that matches each pair of assumptions. North Coast species South Coast species You think starfish shape changes via evolution easily enough, but it's exceedingly rare for starfish to move between coasts. You think starfish can move between coasts easily enough, but it's exceedingly difficult for evolution to change starfish shape. b. Questions b, c, and d all refer to the phylogeny at right. This phylogeny suggests starfish have migrated between coasts... once / twice / depends Circle one, and explain. Р Q R S T 14 c. The same phylogeny at right suggests the spikey shape of Q and T is... Circle one, and explain. homologous / homoplasious / unclear (equally parsimonious) d. What evidence from species S would suggest that the spikey shape of Q and T is homologous?

Answer 1

B) Twice.

This is because the earliest species P is present at North coast. This suggest the common anscestor from which it has diverged was also on this coast initially.

Now, anscestor of Q and R,S,T group continues to live on north coast like P, as a result when Q diverged it also remains north.

Now , the anscestor of R,S,T clade migrates for the 1st time to south coast.

As a result, the 1st diverged T species lives on South only , and S and R clade anscestor continues to live on South coast, when it diverged to S and R , R remains on South coast, and S migrates to North coast again.

Thus, there is 2 migrations in total.

C) the shape of Q and T is homologous.

Reason- anscestor Q and R,S,T clade has spike shape, as a result descendent Q remains spike shaped, Now the shape remains spiked until anscestor of R,S,T from which descendent T gets spike shape.

This shape if again changed as a homoplasy in anscestor of S and R.

D) since the shape of S species is a homoplasy, means it has parallely originated again, this explains that the anscestor of R,S,T clade had the spike shape, T species inherited it from him, but homoplasy occured in the anscestor of R and S, as a result both show different shape from T species.

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