Use of Biological Resources · 6 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 9% of your exam marks.
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.
| 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 |
Wheat and other cereals
Modern wheat is descended from wild grasses that produced only a tiny ear of grain. Over thousands of years, farmers selected for:
The "Green Revolution" of the 1960s used selective breeding to produce dwarf wheat and rice varieties that doubled or tripled global yields and saved hundreds of millions of people from famine. Norman Borlaug won the Nobel Peace Prize in 1970 for this work.
Wild brassica → many vegetables
A single wild species, wild cabbage (Brassica oleracea), has been bred in different directions to produce a whole family of vegetables:
| Vegetable | Selected for |
|---|---|
| Cabbage | Large terminal bud (forms the leafy head) |
| Broccoli | Large flower buds (the "florets") |
| Cauliflower | Sterile flower clusters (the "curd") |
| Brussels sprouts | Many small lateral buds along the stem |
| Kale | Large flat leaves |
| Kohlrabi | Swollen stem base |
All of these are the same species. They can interbreed and produce viable offspring, but they look completely different because each variety was bred for a different feature of the plant. The same trick has been used with other species: tomatoes come in dozens of varieties, all bred from the same wild ancestor.