Draw and interpret phylogenetic trees - AP Biology - Free Printable

This image presents a data table used in biological classification, specifically for constructing a phylogenetic tree. The task is to analyze the shared derived characters (synapomorphies) among different organisms to determine their evolutionary relationships.

Let me break down the problem and solve it step by step.

Step 1: Understand the Table

The table shows five organisms (Lion, Fish, Scorpion, Jellyfish, Sea urchin) and five shared derived characters (Deuterostome, Backbone, Hair, Segmentation, Three tissue layers). A "1" indicates the organism possesses that character, while a "0" means it does not.

Step 2: Identify Key Characters and Groupings

- Three tissue layers: All organisms except Jellyfish have this, indicating Jellyfish is the most distantly related.
- Deuterostome: Lion, Fish, and Sea urchin are deuterostomes. Scorpion and Jellyfish are not.
- Backbone: Only Lion and Fish have a backbone, placing them together as vertebrates.
- Hair: Only the Lion has hair, making it unique among these.
- Segmentation: Lion, Fish, and Scorpion show segmentation, while Jellyfish and Sea urchin do not.

Step 3: Build the Phylogenetic Tree

Based on the shared derived characters, we can infer the following evolutionary relationships:

1. Jellyfish is the outgroup because it lacks all the advanced features (no three tissue layers, no segmentation, etc.).
2. Sea urchin shares the "three tissue layers" and "deuterostome" traits with Lion and Fish but lacks a backbone and segmentation, placing it as a deuterostome but non-vertebrate.
3. Scorpion shares "segmentation" and "three tissue layers" with Lion and Fish but is not a deuterostome, placing it as a protostome with segmentation.
4. Fish and Lion are both vertebrates (have a backbone) and deuterostomes. Lion also has hair, which is a derived trait unique to mammals.

Step 4: Construct the Tree

The phylogenetic tree would look like this:

```
┌── Jellyfish
│
├── Sea urchin
│
├── Scorpion
│
└──┬── Fish
└── Lion
```

Explanation:

- Jellyfish branches off first because it lacks the most basic derived characters.
- Sea urchin branches next as it shares some traits (three tissue layers, deuterostome) but not others (backbone).
- Scorpion branches off as it shares segmentation and three tissue layers but is not a deuterostome.
- Fish and Lion are closest relatives, sharing backbone and deuterostome traits, with Lion being more derived due to having hair.

This analysis helps us understand the evolutionary history and relationships among these organisms based on their shared derived characteristics.