Solved Name Evolutionary Relationships & Phylogenies | Chegg.com - Free Printable

Let's solve this Evolutionary Relationships & Phylogenies Worksheet step by step. We are given a table of five animal taxa and five characteristics (traits), each coded as "1" (present) or "0" (absent). We need to use this data to label a phylogenetic tree based on shared derived traits (synapomorphies).

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Step 1: Analyze the Character Table

| Taxon | Four limbs | Amnion | Pre-orbital fenestra | Hair | Feathers |
|--------|------------|--------|----------------------|------|----------|
| Trout | 0 | 0 | 0 | 0 | 0 |
| Lizard | 1 | 1 | 1 | 0 | 0 |
| Duck | 1 | 1 | 1 | 0 | 1 |
| Toad | 1 | 0 | 0 | 0 | 0 |
| Rabbit | 1 | 1 | 0 | 1 | 0 |

We'll interpret these traits in evolutionary terms.

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Step 2: Understand the Traits

- Four limbs: Present in all tetrapods (lizard, duck, toad, rabbit), absent in trout.
- Amnion: A membrane that protects the embryo; present in reptiles, birds, mammals (lizard, duck, rabbit), absent in fish and amphibians (trout, toad).
- Pre-orbital fenestra: A hole in the skull before the eye; found in reptiles and birds (lizard, duck), not in mammals or amphibians.
- Hair: Only in mammals (rabbit).
- Feathers: Only in birds (duck).

These traits help us determine derived characters (evolutionary novelties) that define clades.

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Step 3: Build the Tree Based on Shared Derived Traits

We will use parsimony — assume the fewest evolutionary changes.

#### Outgroup: Trout
- Trout has no derived traits (all zeros).
- So it is the most distantly related (basal taxon).
- All other animals share at least one trait with each other but not with trout.

So the first split must be:
- Trout vs. all others (tetrapods)

Thus, the first derived trait (A) must be four limbs, which evolved after trout diverged.

> ✔ A = Four limbs

Now we have four tetrapods: Lizard, Duck, Toad, Rabbit

Let’s compare:

- Toad lacks amnion and pre-orbital fenestra → likely more basal than lizard/duck/rabbit
- Lizard and Duck both have amnion, pre-orbital fenestra → they are closely related
- Rabbit has amnion, no pre-orbital fenestra, has hair
- Duck has feathers

So let’s look for shared derived traits.

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Step 4: Trace Evolutionary Changes

We’ll go from root to tips.

#### Node A (after Trout splits):
- Trait: Four limbs → shared by all tetrapods (lizard, duck, toad, rabbit)
- So A = Four limbs

#### Next split: Toad vs. (lizard, duck, rabbit)

- Toad has no amnion, no pre-orbital fenestra, no hair, no feathers
- Lizard, duck, rabbit all have amnion → so amnion evolved here
- But toad lacks amnion → so amnion is a derived trait shared by lizard, duck, rabbit

So B = Amnion

Wait — but pre-orbital fenestra is also shared by lizard and duck, but not rabbit.

Let’s see:

- Toad → no amnion, no fenestra → basal among tetrapods
- So the split is:
- Toad (amphibian)
- Then: amniotes (lizard, duck, rabbit)

So B = Amnion

Now within amniotes: lizard, duck, rabbit

- Lizard and duck both have pre-orbital fenestra → shared derived trait
- Rabbit does not have it → so fenestra evolved in lineage leading to lizard + duck
- Rabbit has hair, duck has feathers

So:
- C = Pre-orbital fenestra (shared by lizard and duck)
- Then, D = Hair (only in rabbit)
- E = Feathers (only in duck)

But wait — let’s map it correctly.

Let’s reconstruct the tree structure.

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Tree Structure Interpretation

The tree looks like:

```
┌── 1. _________
│
├── A. _________
│
├── B. _________
│ ┌── C. _________
│ │
│ ├── D. _________
│ │
│ └── E. _________
│
└── 2. _________
│
├── 3. _________
│
└── 4. _________
│
└── 5. _________
```

Wait — actually, looking at the diagram:

It seems like:

- Root splits into:
- Left branch: Trout
- Right branch: All others

Then, on the right side:

- First split: Toad vs. (Lizard, Duck, Rabbit)

So:

- A = trait shared by Toad, Lizard, Duck, Rabbit → Four limbs
- B = trait shared by Lizard, Duck, Rabbit → Amnion
- Then split between:
- Lizard + Duck (both have pre-orbital fenestra)
- Rabbit (has hair)

So:
- C = Pre-orbital fenestra (shared by lizard and duck)
- D = Hair (in rabbit)
- E = Feathers (in duck)

But wait — feathers are only in duck, so it should be on the duck branch.

Similarly, hair is only in rabbit.

So let’s assign the letters:

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Assigning Letters to Traits

Let’s walk through the tree:

1. Root → Trout (no derived traits)
2. Split 1: Trout vs. Tetrapods
- A = Four limbs (evolved here, shared by all tetrapods)
3. Split 2: Toad vs. Amniotes
- B = Amnion (evolved here, shared by lizard, duck, rabbit)
4. Split 3: Lizard + Duck vs. Rabbit
- C = Pre-orbital fenestra (shared by lizard and duck, not rabbit)
5. Split 4: Duck vs. Lizard
- D = Feathers (only in duck)
6. Split 5: Rabbit
- E = Hair (only in rabbit)

Wait — but in the diagram, there are five numbers (1–5) on the far right, and letters A–E near tick marks.

Let’s re-express the tree:

```
┌─────────────── 1. _______
│
│ ┌────── A. _____
│ │
│ ├────── B. _____
│ │
│ │ ┌────── C. _____
│ │ │
│ │ ├────── D. _____
│ │ │
│ │ └────── E. _____
│ │
│ └────── 2. _______
│
└─────────────── 3. _______
│
└────── 4. _______
│
└────── 5. _______
```

Actually, better to interpret it as:

- The tick marks (A–E) represent derived traits at nodes.
- The numbers 1–5 are labels for the tips (taxa).

So:

- Number 1: Trout
- Number 2: Toad
- Number 3: Lizard
- Number 4: Duck
- Number 5: Rabbit

Now, the tick marks (A–E) are synapomorphies at branching points.

Let’s build the tree:

1. Trout (number 1) is sister to all others → no derived traits at base
2. Four limbs evolved at the node uniting all tetrapods → A = Four limbs
3. Amnion evolved at the node uniting Lizard, Duck, Rabbit → B = Amnion
4. Pre-orbital fenestra evolved at the node uniting Lizard and Duck → C = Pre-orbital fenestra
5. Feathers evolved in Duck → D = Feathers
6. Hair evolved in Rabbit → E = Hair

But wait — the tree has only five tick marks: A, B, C, D, E.

And five tip labels: 1–5.

So:

- 1. Trout
- 2. Toad
- 3. Lizard
- 4. Duck
- 5. Rabbit

Now, let’s map the traits:

- A is on the branch leading to Toad, Lizard, Duck, Rabbit → so Four limbs (since trout lacks them)
- B is on the branch leading to Lizard, Duck, Rabbit → Amnion (toad lacks it)
- C is on the branch leading to Lizard and Duck → Pre-orbital fenestra (rabbit lacks it)
- D is on the branch leading to Duck → Feathers (only duck has it)
- E is on the branch leading to Rabbit → Hair (only rabbit has it)

Yes! That matches.

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✔ Final Answer:

#### Label the Tree:

- A. Four limbs
- B. Amnion
- C. Pre-orbital fenestra
- D. Feathers
- E. Hair

#### Tip Labels:

- 1. Trout
- 2. Toad
- 3. Lizard
- 4. Duck
- 5. Rabbit

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Explanation:

We used cladistics (phylogenetic systematics) to infer relationships based on shared derived traits (synapomorphies).

- Trout is the outgroup (no derived traits).
- Four limbs evolved once in the ancestor of all tetrapods (A).
- Amnion evolved in the ancestor of reptiles and mammals (but not amphibians) → B.
- Pre-orbital fenestra evolved in archosaurs/reptiles (lizard and duck) → C.
- Feathers evolved in birds (duck) → D.
- Hair evolved in mammals (rabbit) → E.

This reflects the actual evolutionary history:

- Fish (trout) → Amphibians (toad) → Reptiles (lizard) → Birds (duck) and Mammals (rabbit)

With amniotes (lizard, duck, rabbit) sharing amnion.

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✔ Final Answer Summary:

Letters (derived traits):
- A. Four limbs
- B. Amnion
- C. Pre-orbital fenestra
- D. Feathers
- E. Hair

Numbers (taxa):
- 1. Trout
- 2. Toad
- 3. Lizard
- 4. Duck
- 5. Rabbit

This tree represents the most parsimonious phylogeny based on the character data.