Solved Phylogenetic trees worksheet 1. Consider the | Chegg.com - Free Printable

Let’s go step by step through each question.

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a. Would a group composed only of fungi and Fonticula be monophyletic? Justify your answer.

First, remember: A monophyletic group (also called a clade) includes an ancestor and *all* of its descendants — no more, no less.

Look at the tree:

- Fungi and Fonticula are both connected to node 8.
- But node 8 also leads to Nuclearia.
- So if you take only fungi and Fonticula, you’re leaving out Nuclearia — which is also a descendant of node 8.
- That means this group is not monophyletic, because it doesn’t include *all* descendants of their most recent common ancestor (node 8).

✔ Final justification: No, because their most recent common ancestor (node 8) also gave rise to Nuclearia, so excluding Nuclearia makes the group incomplete → not monophyletic.

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b. Identify a monophyletic group of your choice that includes choanoflagellates. List all of the members of this group and the node of the common ancestor.

Choanoflagellates are on the branch coming from node 10.

Node 10 is the common ancestor of:
- Choanoflagellates
- Sponges
- Insects
- Vertebrates

Wait — let’s trace carefully.

Actually, looking again:

- Node 10 connects to:
- Choanoflagellates (directly)
- And then to node 11, which leads to:
- Sponges
- Node 12 → which leads to Insects and Vertebrates

So the full group descending from node 10 includes:
→ Choanoflagellates, Sponges, Insects, Vertebrates

That’s a monophyletic group! All share node 10 as their most recent common ancestor.

You could also pick a smaller one — like just “Animals” (which includes Sponges, Insects, Vertebrates), but that does NOT include choanoflagellates.

So to include choanoflagellates, we must go back to node 10.

✔ Members: Choanoflagellates, Sponges, Insects, Vertebrates
✔ Common ancestor node: 10

(Note: Some might argue Capsaspora is also under node 7 or 6 — but choanoflagellates are directly under node 10, and node 10 does NOT include Capsaspora. Capsaspora branches off earlier at node 7.)

Double-checking the tree:

From node 6 → splits into:
- Breviatea
- Node 7 → Capsaspora + Node 8 (Fungi, Fonticula, Nuclearia)
AND
- Node 10 → Choanoflagellates + Node 11 (Sponges, etc.)

Yes — so node 10 is correct for including choanoflagellates and animals.

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c. Which node represents the most recent common ancestor of land plants and animals?

We need to find where the lineages of land plants and animals meet.

- Land plants branch off near the bottom — they come from node 3? Wait, let’s trace.

Looking at the big picture:

The entire right side (Opisthokonts) includes animals, fungi, etc.

Land plants are on the left side — they branch off after node 2, before node 3.

Actually, let’s follow the main trunk:

Root → node 1 → splits into:
- Bacteria
- Then node 2 → splits into:
- Archaea
- Then node 3 → splits into:
- Land plants
- Then the rest (including Opisthokonts, Amoebozoa, etc.)

Wait — actually, looking again:

After node 2, the next split is node 3.

Node 3 leads to:
- Land plants (one branch)
- And the other branch goes to node 4, 5, 6, etc. — which eventually leads to animals.

So the most recent common ancestor of land plants and animals would be the node where their lines first join — that’s node 3.

Because:
- Land plants come directly from node 3.
- Animals come from the other branch of node 3 (via nodes 4, 5, 6, 7, 10, 11, 12, 13...).

So yes — node 3 is the last point where land plants and animals shared a common ancestor.

✔ Answer: Node 3

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Final Answer:

a. No, because fungi and Fonticula share a common ancestor at node 8, but node 8 also gave rise to Nuclearia. Leaving out Nuclearia means the group is not monophyletic.

b. One possible monophyletic group including choanoflagellates is: Choanoflagellates, Sponges, Insects, and Vertebrates. Their common ancestor is node 10.

c. Node 3