IB Biology D4.1 Natural selection: practice questions

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D4.1-01 · Paper 1A style · multiple choice · 1 mark

Where variation comes from

Which statements about the sources of the variation that natural selection acts on are correct?
I. Crossing over and the random orientation of bivalents during meiosis produce new combinations of existing alleles.
II. Fusion of gametes from two parents creates new alleles.
III. Mutation is the original source of new alleles. [1]

1. I only
2. II only
3. I and III only
4. I, II and III

Show the answer and the reasoning

Answer: C. C is correct. Mutation is the only process that creates new alleles (III). Sexual reproduction reshuffles alleles that already exist: crossing over and the random orientation of bivalents during meiosis, and the fusion of gametes from two parents, produce new combinations (I). Statement II is false because fertilization combines existing alleles but does not change any base sequence, which rules out B and D. A leaves out mutation, the original source of all genetic variation.

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The 5 questions in D4.1

1. D4.1-01 Where variation comes fromPaper 1A style · multiple choice · 1 mark
2. D4.1-02 Costly plumagePaper 1A style · multiple choice · 1 mark
3. D4.1-03 Hardy-Weinberg flower countPaper 1A style · multiple choice · 1 mark · HL
4. D4.1-04 Resistance in a hospitalPaper 2 style · short answer · 7 marks
5. D4.1-05 Sickle-cell allele and malariaPaper 1B style · data-based · 9 marks · HL

More of D Continuity and change

• D1.1 DNA replication
• D1.2 Protein synthesis
• D1.3 Mutation and gene editing
• D2.1 Cell and nuclear division
• D2.2 Gene expression
• D2.3 Water potential
• D3.1 Reproduction
• D3.2 Inheritance
• D3.3 Homeostasis
• D4.2 Stability and change
• D4.3 Climate change

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.