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.
| Goal | Examples |
|---|---|
| Higher meat yield | Cattle, sheep, pigs, chickens bred for fast growth and large body size |
| Higher milk yield | Dairy cows (Holstein-Friesians produce 30+ litres of milk per day) |
| Higher egg production | Laying hens (produce around 300 eggs per year, vs ~50 for wild birds) |
| Quality of wool | Sheep (Merino wool is fine and soft thanks to centuries of selection) |
| Quality of meat | Marbled beef (Wagyu cattle), tender lamb |
| Speed | Racehorses (Thoroughbreds) |
| Temperament | Domestic dogs (gentle, trainable) |
| Appearance | Show dogs, cats, horses, pigeons |
Dairy cows
Modern dairy breeds like Holstein-Friesians produce around 30 litres of milk per day, several times what a wild cow could produce. Selective breeding has favoured:
Beef cattle
Breeds like Aberdeen Angus and Hereford have been bred for:
Chickens
Modern broiler chickens reach slaughter weight in just 6 weeks, compared with 16+ weeks for traditional breeds. Selected for:
Laying hens have been bred separately for egg production: a modern hen lays around 300 eggs per year, compared with maybe 50 for a wild jungle fowl.
Sheep
Different breeds have been selected for different products:
Every breed of domestic dog, from a Chihuahua to a Great Dane, is descended from grey wolves about 15 000 years ago. Yet they have been bred into wildly different shapes, sizes, coat types and behaviours:
All breeds can still interbreed and produce fertile offspring, so they are still one species: Canis familiaris.
Farmed fish (salmon, trout, tilapia, carp) are selectively bred too, for:
The use of selective breeding alongside controlled water quality, feeding and disease control allows fish farms to produce far more fish per cubic metre than wild populations could ever sustain. Fish farming is covered in more detail in topic 16 (Human Impact on the Environment).