Question

SCIENTIFIC INQUIRY • DRAW IT (a) Draw a phylogenetic tree based on characters 1–5 in the table below. Place hatch marks on the tree to indicate the origin(s) of characters 1–6. (b) Assume that tuna and dolphins are sister species and redraw the phylogenetic tree accordingly. Use hatch marks to indicate the origin(s) of characters 1–6. (c) Determine how many evolutionary changes are required in each tree. Identify the most parsimonious tree.

Short answer

(a) The phylogenetic tree is prepared based on the characters 1 and 5 that are present in the table. The characters are backbone and milk.

(b) The phylogenetic tree is redrawn by linking tuna and dolphins of the phylogenetic tree as sisters.

(c) In the first phylogenetic tree, seven changes are necessary. In the second phylogenetic tree, nine changes are necessary. The first tree is more parsimonious.

Step-by-step solution

Explanation for part (a)

Characters one and five are linked in the first phylogenetic tree. The hatch marks are placed to indicate how characters one and six have developed. Hence, the hatch mark is placed on tuna because it is the only organism in the tree with both traits.

Step 2: Explanation for part (b)

The phylogenetic is reconstructed to produce a phylogenetic tree in which the dolphins and tuna are sisters. In this tree, dolphins and tuna are placed next to each other, and the hatch marks labeled 3, 4, 5 are placed on the dolphin. In this tree 9 evolutionary changes are observed.

Step 3: Explanation for part (c)

The parsimonious tree among one and two is one. This is due to the fact that phylogenic parsimony is directly dependent on the least number of changes that take place during the course of evolution. Since tree one requires only five changes, it is called a parsimonious tree.