Node — Science definition
Defined in 3 courses:
- A branching point representing a common ancestor; two lineages sharing a recent node are more closely related than either is to one branching earlier. (Life Science & Scientific Inquiry)
- A branching point representing a common ancestor in a tree model. (Life Science: Biology)
- A position of zero displacement in an ideal standing wave. (Physics & Environmental Science)
Where it is taught
- Common Ancestry, Evidence & Branching Trees — Evolution, Evidence & Life History, Life Science & Scientific Inquiry, Grade 7
- Reading Evolutionary Trees — Evolution, Ancestry & Biodiversity, Life Science: Biology, Grade 10
- Superposition, Standing Waves & Resonance — Waves, Sound & Optics, Physics & Environmental Science, Grade 12
In use
A phylogenetic tree summarises the conclusions, with each node representing a common ancestor from which two lineages diverged.
Common Ancestry, Evidence & Branching Trees
A node joins lineages at a common ancestor; taxa sharing a more recent node are more closely related on that tree.
Reading Evolutionary Trees
Questions using node
Problem 1
Does rotating B and C around their node change their relationship?
Answer and explanation
No. The shared node and connections remain the same; visual left-right order is not the ancestry criterion.
Problem 2
In a tree, A and B share a recent node; C joins their branch at an older node. Which pair is most closely related? Explain the reasoning in your own words.
Answer and explanation
A and B are the closest pair in the supplied tree.
Trace the shared ancestors rather than the page spacing.
A and B share the most recent node.
Response criteria
- Use the stated conditions.
- Show the evidence or calculation.
- Explain the conclusion and any stated limitation.
Problem 3
If branches rotate around a node, does common ancestry change? Show the reasoning, not just the conclusion.
Hints
A tree's topology carries relatedness; lengths need a declared scale.
Answer and explanation
No. The same branching connections remain.
Problem 4
Why does rotating two branches around their shared node leave the relationship unchanged?
Answer and explanation
The connectivity and common ancestor are unchanged; only tip display order differs.
Taught alongside
- common ancestor
- homologous structure
- vestigial structure
- phylogenetic tree
- sister lineages
- derived feature
- antinode
- resonance