Selective Breeding is Strong Evidence for Evolution
Definition
Selective breeding
Selective breeding, or artificial selection, is the process by which humans intentionally breed animals or plants to enhance specific traits.
- Selective breeding mirrors the principles of natural selection, but with a key difference:
- Natural selection: Traits are selected by environmental pressures, favoring survival and reproduction.
- Artificial selection: Traits are selected by humans, based on preferences or utility.
By examining domesticated animals and crop plants, scientists can observe evolutionary changes on a much shorter timescale than in the wild.
TipRecognize that in artificial selection, humans are the selective force, choosing traits to amplify.
Steps of Selective Breeding
- A population contains heritable variation due to genetic differences (e.g., mutations, recombination).
- Humans select parents that show traits considered valuable (e.g., high yield, docility, rapid growth).
- These parents are bred together and produce offspring.
- Offspring are screened for the desired traits, and only those with the strongest expression are selected for further breeding.
- Over many generations, the trait becomes fixed in the population.
Examples of Selective Breeding
Domesticated Animals
1. Dogs (Canis lupus familiaris)
- All modern dog breeds descended from gray wolves (Canis lupus).
- Humans selectively bred wolves for traits like size, behavior, and coat type, leading to the wide variety of breeds we see today.
- Siberian Husky: Bred for endurance and pulling sleds.
- Dachshund: Bred for hunting burrowing animals.
- Chihuahua and Great Dane: Dramatically different in size due to selection for extreme traits.
2. Chickens
- Modern egg-laying hens produce hundreds of eggs annually, while their wild ancestor, the red junglefowl, lays only a few eggs per year.
Domesticated Crops
1. Maize (Corn)
- Modern maize evolved from a wild grass called teosinte.
