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D4.1.7—Sexual selection

Sexual selection favours traits that increase mating success, even when those traits may reduce survival in evolving populations in evolving populations.

Syllabus
First assessment 2025
Objective
D4.1.7
Level
HL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceNovember 2020
Most common paperPaper3
Typical marks3

Common command terms

  • Explain
  • Suggest
  • Evaluate

Recent exam appearances

November 2020Paper3 ["HL"] · TZ08(b)[ 3 ]D4.1.7—Sexual selection
November 2020Paper3 ["HL"] · TZ08(a)[ 2 ]D4.1.7—Sexual selection
November 2019Paper3 ["HL"] · TZ07(b)[ 3 ]D4.1.7—Sexual selection
November 2018Paper3 ["HL"] · TZ07(a)[ 3 ]D4.1.7—Sexual selection
November 2013Paper3 ["HL"] · TZ06[ 6 ]D4.1.7—Sexual selection
Practice this objective

Coverage 2013–2020 · Updated 16 Jul 2026

Sexual Selection Favors Mating Success

Sexual selection is selection for traits that increase access to mates or fertilization success, even when they carry survival costs.

Mate choice and competition among same-sex individuals change reproductive success. The trait spreads when its mating advantage outweighs its costs.

Separate survival benefit from mating benefit before explaining a conspicuous trait.; separate variation, selection, inheritance and time

Peacock tail feathers may attract mates while making escape harder, so mating success can favour the tail despite predation risk. This gives a concrete prediction from the stated population.

Sexual selection is one component of natural selection, not a guarantee that the trait improves survival. Interpret the result within the stated selection model and evidence limits.

Sexual selection

Assessment in practice

2–3 marks
How it is assessed

This objective is assessed through essay response, commonly using Explain / Suggest / Evaluate.

Command terms

Explain / Suggest / Evaluate

What earns marks

Build the answer around this relationship: Sexual selection acts through mating success.

Representative question

Question 1

[Maximum number: 6]

Explain what is meant by exaggerated traits and how they may develop in males of a species.

Retrieve the Core Natural Selection Route

Core D4.1 examples follow the same causal route: heritable variation exists, a selection pressure acts, individuals differ in fitness, and alleles linked to higher reproduction become more common. Endler’s guppies and sexual selection are evidence versions of the same chain.

  • mutation creates alleles; meiosis and fertilization reshuffle combinations
  • overproduction, limited resources, and abiotic factors filter variants
  • passing alleles to offspring in a particular environment
  • Endler controlled predation pressure and guppy colour patterns changed

Core Natural Selection

Core natural-selection exam answers should never stop at “the best adapted survive.” They need the chain: heritable variation exists, a named pressure acts, some individuals have higher fitness, and their alleles become more common over generations. Use this for abiotic pressure, overproduction, sexual selection, and Endler-style data.

  • Explain natural selection using heritable variation, selection pressure, differential survival/reproduction, and population change.
  • Distinguish mutation/recombination as sources of variation from selection as the filtering process.
  • Use examples such as abiotic pressure, sexual selection, or Endler guppy data to support the chain.

Concept essentials

  • Sexual selection acts through mating success.
  • A trait can spread if it increases reproduction despite survival costs.
  • Mate choice and competition for mates are common sexual selection mechanisms.