Unit 1: Unity and Diversity
Topic 1.7: Classification and Cladistics (HL) Questions
Practice 20 exam-style questions for IB Biology Topic 1.7. Review the question stems below, then unlock the full Question Bank to access markschemes, model answers, and AI grading.
1Define1 mark
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Define the term monophyletic group.
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On a cladogram, what does a node (branch point) represent?
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State what a single node (branch point) on a cladogram represents.
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Modern cladograms are built mainly from which type of evidence?
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Two groups on a cladogram are MOST closely related when their branches meet at which point?
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State the term used for a group that consists of a common ancestor together with all of its descendants.
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State one named example of a group of organisms that has been reclassified because of cladistic evidence, and give the type of group it had wrongly been.
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State two types of molecule whose sequences can be compared between species to provide molecular evidence of how closely they are related.
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What does the root of a cladogram represent?
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Two species' DNA base sequences for the same gene show MANY differences.
What does this suggest about the two species?
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Cladistics groups organisms primarily on the basis of which type of evidence?
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Which statement best describes how biologists now view a classification scheme built using cladistics?
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An insect long placed in genus A is moved to genus B after DNA shows its closest relatives are the genus-B species.
Why was the move necessary?
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On a cladogram of four groups, one group's branch joins the others only at the root, while the other three share more recent nodes.
What does this tell you about that group?
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The figwort family (Scrophulariaceae) was split into several smaller families after DNA analysis.
What did the DNA most likely reveal?
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The cladogram shows the closest living relatives of birds.
Which conclusion does this evidence support?
[Diagram: bio-cladogram]
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The cladogram shows four species placed using sequence differences.
A human's haemoglobin differs least from the gorilla's, more from the monkey's and most from the lemur's.
Which species is placed as the human's CLOSEST relative, and why?
[Diagram: bio-cladogram]
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A traditional group called 'reptiles' that deliberately leaves out the birds is best described as:
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