Solved Worksheet Phylogenetic Trees BIOL R122 Instructions ... - Free Printable

Problem Analysis:

The task involves analyzing three phylogenetic trees and determining which one is the most parsimonious based on the given character data. Parsimony is a principle in phylogenetics that favors the simplest explanation, i.e., the tree that requires the fewest evolutionary changes to explain the observed differences among species.

#### Given Data:
- Ancestor: Body shape (round), Body color (orange), Head color (white), Antenna (yes), Jaw visible (no), Spots (yes).
- Species A: Body shape (round), Body color (orange), Head color (black), Antenna (yes), Jaw visible (yes), Spots (yes).
- Species B: Body shape (round), Body color (yellow), Head color (black), Antenna (yes), Jaw visible (no), Spots (no).
- Species C: Body shape (oval), Body color (yellow), Head color (white), Antenna (no), Jaw visible (yes), Spots (yes).

#### Phylogenetic Trees:
We are provided with three possible phylogenetic trees (Tree #1, Tree #2, and Tree #3). Our goal is to evaluate each tree based on the number of evolutionary changes required to explain the observed differences.

---

Step 1: Understanding Parsimony

Parsimony seeks to minimize the total number of evolutionary changes across all characters. To evaluate this, we will:
1. Compare the traits of each species to the ancestor.
2. Count the number of changes required for each tree.
3. Identify the tree with the fewest total changes.

---

Step 2: Evaluate Each Tree

#### Tree #1
- Branching Order: Ancestor → (A, B) → C
- Changes:
- Body shape:
- From round (ancestor) to oval (C): 1 change.
- Body color:
- From orange (ancestor) to yellow (B and C): 2 changes.
- Head color:
- From white (ancestor) to black (A and B): 2 changes.
- Antenna:
- From yes (ancestor) to no (C): 1 change.
- Jaw visible:
- From no (ancestor) to yes (A and C): 2 changes.
- Spots:
- From yes (ancestor) to no (B): 1 change.
- Total Changes: \(1 + 2 + 2 + 1 + 2 + 1 = 9\)

#### Tree #2
- Branching Order: Ancestor → (B, C) → A
- Changes:
- Body shape:
- From round (ancestor) to oval (C): 1 change.
- Body color:
- From orange (ancestor) to yellow (B and C): 2 changes.
- Head color:
- From white (ancestor) to black (A and B): 2 changes.
- Antenna:
- From yes (ancestor) to no (C): 1 change.
- Jaw visible:
- From no (ancestor) to yes (A and C): 2 changes.
- Spots:
- From yes (ancestor) to no (B): 1 change.
- Total Changes: \(1 + 2 + 2 + 1 + 2 + 1 = 9\)

#### Tree #3
- Branching Order: Ancestor → (A, C) → B
- Changes:
- Body shape:
- From round (ancestor) to oval (C): 1 change.
- Body color:
- From orange (ancestor) to yellow (B and C): 2 changes.
- Head color:
- From white (ancestor) to black (A and B): 2 changes.
- Antenna:
- From yes (ancestor) to no (C): 1 change.
- Jaw visible:
- From no (ancestor) to yes (A and C): 2 changes.
- Spots:
- From yes (ancestor) to no (B): 1 change.
- Total Changes: \(1 + 2 + 2 + 1 + 2 + 1 = 9\)

---

Step 3: Compare the Trees

All three trees (Tree #1, Tree #2, and Tree #3) require the same total number of evolutionary changes (9 changes). Since there is no difference in parsimony among the trees, any of them could be considered equally likely based on the given data.

---

Final Answer:

Since all three trees have the same number of evolutionary changes, none can be definitively chosen as more parsimonious than the others. However, if forced to choose, any of the trees could be selected. For the sake of this problem, let's assume Tree #1 is chosen arbitrarily.

\[
\boxed{\text{Tree #1}}
\]