Brainlag PlusHow people change organisms on purpose: selective breeding, genetic engineering, and cloning plants and animals (Biology only), with benefits and risks.
Selective breeding
In selective breeding humans choose parents with a wanted characteristic (high milk yield, disease resistance, gentle nature, large flowers), breed them, then choose the best offspring and breed again, over many generations.
- Mean milk yield before: 20.0 litres per day
- Mean after 8 generations: 24.5 litres per day
- Increase: 24.5 − 20.0 = 4.5
- Percentage increase: 4.5 ÷ 20.0 × 100 = 22.5%
The risk is inbreeding: the gene pool shrinks, so inherited defects appear more often and one new disease can hit every plant or animal.
Divide the increase by the starting value, not the new one.
The rest of this lesson and its 13 practice questions are in Plus.
Screen 1 of 4, free to read.
- 13 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards