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A4.1.10 (HL)—Barriers to hybridization

Barriers to hybridization prevent gene flow before or after fertilization, maintaining species boundaries between potentially interbreeding populations over evolutionary time.

Syllabus
First assessment 2025
Objective
A4.1.10
Level
HL

Concept essentials

  • Prezygotic barriers prevent mating or fertilization before a zygote forms.
  • Temporal, behavioural and habitat isolation can stop hybridization before fertilization.
  • Postzygotic barriers reduce hybrid survival or fertility after fertilization.
  • Hybrid infertility maintains species boundaries by preventing gene flow through fertile offspring.
ConceptIB Biology HL