IB Biology SL 3.1.4 Cladistics and Species Concepts
Practise IB Biology SL 3.1.4 by defining species and interpreting fertility, morphology and reproductive-isolation evidence.
- Syllabus
- First assessment 2025
- Course
- Biology SL
- Level
- SL
Exam points
- Define species using interbreeding and fertile offspring, then discuss hybrids and asexual organisms as limits.
- Use morphology, fertility and genetic evidence to judge whether populations belong to one species.
- Interpret species data to distinguish reproductive isolation from superficial similarity.
A3.1.4—Biological species concept question 1
[Maximum number: 3]
Discuss the definition of the term species.
meaning of species has changed over time / no longer just based on morphological features/phenotype; species members also resemble each other in physiology/biochemistry/DNA sequences/use of habitat/behaviour; but species can evolve and features change/species gradually split up; definition now based on ability to interbreed/produce viable, fertile offspring; gene flow among populations of the species maintains the species' uniqueness; some interspecific hybrids are fertile making categorization difficult; further accurate discussion point about species definition;
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