Constructing and reading cladograms
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Question
What is a cladogram?
Answer
A branching **tree-diagram** showing the **most probable evolutionary relationships** among groups (clades), based on the best current evidence.
Question
What does a node on a cladogram represent?
Answer
A **common ancestor** — the point where one ancestral lineage **diverged (split)** into two lineages.
Question
How do you find the two most closely related groups?
Answer
Find the pair whose branches meet at the **most recent node** (nearest the tips) — they share the **most recent common ancestor**.
Question
What is the root of a cladogram?
Answer
The **deepest (oldest) node**, on the far left — the **common ancestor of every group** on the tree.
Question
Why are some groups more distantly related than others?
Answer
Their branches meet only at a **deep node (near the root)**, so their **common ancestor is much older** — they diverged earlier.
Question
Why is a cladogram only a hypothesis?
Answer
It shows the **most probable** relationships from the **evidence available** (now mainly DNA). New evidence can lead to it being **revised**.
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Full study notes for Constructing and reading cladograms
Topic 1.7 hub
Classification and cladistics
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