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IB Biology HL A2.3 Viruses Hl Only Questions

Practise IB Biology HL A2.3 across virus structure, replication cycles and rapid evolution, using route-specific questions and mark-scheme evidence.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • identify common viral structure using a DNA or RNA genome, protein capsid, absent cytoplasm and absent ribosomes
  • explain obligate parasitism and non-living classification from host dependence, absent metabolism and cellular reproduction
  • identify capsids and visible viral components in labelled images or electron micrographs
  • compare viral genomes, capsid architectures and envelope status using lambda phage, HIV, TMV or coronavirus examples
  • justify vaccine strategies from viral DNA or RNA, capsid proteins and attenuation or inactivation
  • compare lambda lytic and lysogenic cycles using DNA injection or integration, host machinery, assembly and lysis
  • explain prophage replication through binary fission and stress-induced excision into the lytic cycle
  • explain rapid viral evolution through mutation without proofreading, recombination or horizontal gene transfer and short generation times
  • use viral variation, natural selection and immune escape to explain antigenic change and effects on vaccines or secondary responses

Covered syllabus points

A2.3.1 (HL)—Common structural featuresA2.3.2 (HL)—Diversity of virus structureA2.3.3 (HL)—Lytic cycleA2.3.4 (HL)—Lysogenic cycleA2.3.5 (HL)—Several origins of virusesA2.3.6 (HL)—Rapid evolution in viruses

Question 1

[Maximum number: 1]

The table shows the number of amino acids that are different in the sequences of the protein FOXP2 from a human compared with four other primate species.

Table for Question 1 — IB Biology HL

Some infectious diseases in humans are caused by viruses that originated in other primates.

State one structural feature of a virus.

Question 2

[Maximum number: 7]

At all levels of biological organization there is diversity.

Describe, with examples, the diversity of structure in viruses.

Question 3

[Maximum number: 3]

The micrograph is an image of human cheek cells viewed with a light microscope.

Figure for Question 3 — IB Biology HL

Viruses depend on living cells to reproduce. Compare and contrast the lysogenic and lytic cycles of the bacteriophage lambda.

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