Selective breeding

• Selective breeding is the process by which humans have intentionally chosen which animals or plants to reproduce together so that the offspring show desired characteristics
• • The desired characteristics are identified
  • Only the individuals showing those characteristics are bred together
  • Only the offspring exhibiting the desired characteristics are bred
  • This is repeated over several generations until all the population have the desired trait
• Examples in animals:

  • Hens that lay big eggs of a particular colour
  • Animals with bigger muscle mass for more meat
  • Cows that produce large quantities of milk
  • Dogs bred for their behaviour, intelligence (border collies), cuteness (pugs)
  • Racehorses bred for speed
• Examples in plants:

  • Crops that produce a larger yield
  • Crops that are resistant to certain diseases
  • Flowers bred for size, shape or colour
  • Plants with sweeter fruit
  • Bananas without seeds
  • Wheat with shorter stems
• Positives:

  • Better quality and variety of food
  • It can produce a higher yield for farmers growing crops or raising animals
  • Can produce crops resistant to pests and disease
  • Does not involve genetic modification so it is deemed safer
  • Keeps a desirable trait in the population, or eliminates an unwanted trait
• Negative:

  • Inbreeding can result in disease caused by recessive alleles
  • Can cause harm to animals and produce health problems
  • Less genetic variation - less able to withstand changes in the environment or a new disease
  • Can be slow because it needs to be repeated over several generations, and no guarantee the trait will be passed onto offspring
  • May lose the traits not selected for permanently