Home / IB DP Biology- A3.2 Classification and cladistics-IB Style Questions For HL Paper 1A

IB DP Biology- A3.2 Classification and cladistics-IB Style Questions For HL Paper 1A -New Syllabus

IBDP Biology HL Paper 1 -All Chapters

Question

The diagram shows a phylogenetic tree. Which encircled area shows a clade?

▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{D}} \)

A clade consists of a common ancestor and all of its descendants. In the diagram, only area D includes a single ancestor together with every branch that arises from it, so it represents a true clade.

Question

The following cladogram illustrates the evolutionary relationships among several vertebrates.

Based on the cladogram, which of the following conclusions can be made?

A. Tortoises do not possess lungs.
B. A tortoise and a tarsier share a closer evolutionary relationship than a tiger and a tarsier.
C. A toad and a tuna are more closely related than a tiger and a tuna.
D. Tigers possess both fur and 5-digit hands.

▶️ Answer/Explanation
The cladogram shows that the tuna diverged first, while the toad shares a more recent common ancestor with other terrestrial animals.
This indicates that the toad and tuna are more closely related to each other than either is to the tiger, which diverged later and possesses additional traits such as fur.
✅ Answer: (C) A toad and a tuna are more closely related than a tiger and a tuna.

Question

Domain is a taxonomic level above kingdom that classifies living organisms into three groups. What provided the evidence for classification into domains?

(A) Ribosomal RNA (rRNA) base sequences
(B) Mitochondrial DNA base sequences
(C) Cell wall structure
(D) Amino acid sequence of ATP synthase
▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{A}} \)

The three-domain classification system (Bacteria, Archaea, and Eukarya) was established by comparing ribosomal RNA (rRNA) base sequences. rRNA evolves slowly and is present in all organisms, making it an excellent molecule for determining evolutionary relationships.

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