Phylogenetic Tree Worksheet 2 - Practice Problems 1. What trait ... - Free Printable

Absolutely! Let’s walk through each question using the first cladogram (the one with Lancelet, Lamprey, Tuna, Salamander, Turtle, Leopard). I’ll explain how to read the cladogram and then answer each question.

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🔍 How to Read a Cladogram:

- Each branch point (node) represents a common ancestor that had a new trait (called a derived trait).
- Organisms that share a more recent branch point are more closely related.
- Traits listed on the branches are shared by all organisms to the right of that trait.
- The outgroup (Lancelet) is the least related and helps root the tree.

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## ✔ Answers & Explanations:

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1. What trait separates Lampreys from tuna on this cladogram?

➡️ Jaws

Explanation:
- Look at the branch leading to Lamprey — it splits off before the “Jaws” trait appears.
- Tuna is after the “Jaws” trait, meaning tuna has jaws, but lampreys do not.
- So, jaws is the trait that separates them.

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2. What separates a salamander from a turtle?

➡️ Amniotic egg

Explanation:
- Salamander branches off *before* the “Amniotic egg” trait.
- Turtle branches off *after* “Amniotic egg”, meaning turtles have amniotic eggs, but salamanders (amphibians) do not.
- So, amniotic egg is the key trait separating them.

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3. Which organism is most related to the leopard?

➡️ Turtle

Explanation:
- On the cladogram, the leopard shares the most recent common ancestor with the turtle — they both come after “Four walking legs”, “Amniotic egg”, and “Jaws”.
- Salamander branches off earlier (before amniotic egg), so it’s less related.
- Tuna and lamprey are even farther back.
- So, turtle is the closest relative shown here.

*(Note: In real biology, leopards are mammals and more closely related to other mammals, but in THIS cladogram, turtle is the closest because it shares the most recent node with leopard.)*

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4. What 4 traits do these two organisms share?

*(Assuming “these two organisms” refers to the two most closely related — Leopard and Turtle — since no specific pair is named, but contextually it makes sense.)*

➡️ Vertebral column, Jaws, Four walking legs, Amniotic egg

Explanation:
- Both leopard and turtle are to the right of all these traits.
- They both have:
- Vertebral column (all except lancelet)
- Jaws (all except lancelet and lamprey)
- Four walking legs (salamander, turtle, leopard)
- Amniotic egg (turtle and leopard)

*(Note: Leopard does NOT have an amniotic egg? Wait — actually, mammals DO have amniotic eggs — it’s just internalized! So yes, they share it.)*

✔ So the 4 shared traits are:
Vertebral column, Jaws, Four walking legs, Amniotic egg

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5. Which organism will have DNA most similar to the turtle?

➡️ Leopard

Explanation:
- DNA similarity correlates with evolutionary closeness.
- Turtle and leopard share the most recent common ancestor among all listed organisms.
- Therefore, leopard will have the most similar DNA to the turtle.

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6. Which organism’s DNA will differ the most from the leopard?

➡️ Lancelet

Explanation:
- Lancelet is the outgroup — it branched off first, before any of the traits like vertebral column or jaws.
- It shares the fewest derived traits with the leopard.
- So, lancelet is the most distantly related → its DNA will differ the most.

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## 🧠 Summary of Answers:

1. Jaws
2. Amniotic egg
3. Turtle
4. Vertebral column, Jaws, Four walking legs, Amniotic egg
5. Leopard *(Wait — that can’t be right for #5… let me double-check.)*

⚠️ Correction for #5:

> 5. Which organism will have DNA most similar to the turtle?

The turtle’s closest relative on the cladogram is the leopard, so YES — leopard is correct.

But wait — if you’re asking “which organism has DNA most similar TO the turtle”, then the answer is still leopard, because they share the most recent common ancestor.

✔ So answer remains: Leopard

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## ✔ Final Answer Key:

1. Jaws
2. Amniotic egg
3. Turtle
4. Vertebral column, Jaws, Four walking legs, Amniotic egg
5. Leopard
6. Lancelet

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Let me know if you’d like help with the second cladogram (“Your Turn”) too — just say the word! 😊