Quiz & Worksheet - Cladograms and Phylogenetic Trees | Study.com - Free Printable

Let’s go step by step through each question.

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Question 1: According to the cladogram shown, which organisms are most closely related?

A cladogram shows evolutionary relationships — organisms that share a more recent common ancestor are closer together on the tree. The ones that branch off from the same point (or very close points) are most closely related.

Looking at the first diagram:

- At the top left, we see Zygogynum, Exospermum, Belliolium, and Bubbina all branching off from nearly the same spot — meaning they’re very closely related.
- Among the answer choices, only “Belliolum and Bubbia” appears as a pair that branches off together near the top.
- “Exosperman and Takhtajan ia” — these are far apart on the tree.
- “Exosperman and Tasmania” — also not close.
- “Belliolum and Drinys” — Drinys is farther down the tree.
- “Exosperman and Drinys” — again, not close.

So, Belliolum and Bubbia are the most closely related among the options given.

✔ Final Answer for Q1: Belliolum and Bubbia

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Question 2: According to the phylogenetic tree, which organisms are the least related to each other evolutionarily?

In a phylogenetic tree, organisms that are on opposite ends of the tree — especially those that split off earliest — are least related.

Looking at the second diagram:

- Arthropoda splits into two main groups: Arachnata (which includes Trilobita and Chelicerata) and Mandibulata (which includes Crustacea, Myriapoda, Insecta).
- So, any organism from Arachnata vs. any from Mandibulata will be less related than pairs within the same group.
- Let’s check the options:
- Trilobita and Insecta: Trilobita is under Arachnata; Insecta is under Mandibulata → different major branches → very distantly related.
- Insecta and Myriapoda → both under Mandibulata → relatively close.
- Insecta and Crustacea → both under Mandibulata → close.
- Trilobita and Chelicerata → both under Arachnata → close.
- Crustacea and Myriapoda → both under Mandibulata → close.

So, Trilobita and Insecta are on completely different main branches → least related.

✔ Final Answer for Q2: Trilobita and Insecta

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Question 3: Which term best describes a group of species without a known common ancestor?

This is about classification terms in biology:

- Polyphyletic = a group that does NOT include the most recent common ancestor of all members — meaning the group was formed by picking species from different lineages, so no single shared ancestor for the whole group.
- Monophyletic = includes an ancestor and ALL its descendants (a true clade).
- Paraphyletic = includes an ancestor but NOT all descendants.
- Lateral and Binomial don’t fit here — binomial refers to naming (like Homo sapiens), lateral isn’t a standard term for this context.

The question says: “a group of species without a known common ancestor” — that matches polyphyletic.

✔ Final Answer for Q3: Polyphyletic

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Final Answers:

1. Belliolum and Bubbia
2. Trilobita and Insecta
3. Polyphyletic