4BI1
Selective Breeding
Use of Biological Resources · 6 question types
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 9% of your exam marks.
stable
Medium
Stable9%
Selective breeding vs natural selection comparisons and examples appear across most papers.
Most of our staple food crops have been transformed by thousands of years of selective breeding.
Common goals for plant breeding
| Goal | Why it matters |
|---|---|
| Higher yield | More food per hectare of farmland |
| Disease resistance | Less crop lost to fungal, viral or bacterial disease |
| Pest resistance | Less reliance on chemical pesticides |
| Drought tolerance | Crops survive in drier climates and use less irrigation |
| Tolerance to extreme temperatures | Crops can be grown in more places |
| Better taste, colour or shelf life | More commercially valuable |
| Larger fruits or grains | More food per plant |
| Shorter growing season | Two or three crops per year instead of one |
Other plant examples
- Apples: selected for sweetness, juice content, colour and shelf life
- Bananas: the supermarket banana is a single variety (Cavendish), selected for size, sweetness, lack of seeds. It is now seriously threatened by Panama disease, partly because every plant in the world is a clone
- Maize (corn): descended from a Mexican grass called teosinte that had tiny ears with just a few grains. Modern maize cobs have hundreds of huge grains
- Roses: bred in thousands of varieties for flower size, colour and scent (rather than for food)