Selective Breeding

Selective breeding / artificial selection

Selective breeding, also known as artificial selection, is the process where humans choose specific organisms (plants or animals) with desirable traits to reproduce, thus passing those traits on to the next generation. This method is used to enhance particular phenotypic features, such as size, flavor, or disease resistance, in plants or animals.

Humans can select organisms with favorable characteristics for breeding. Over time, these desirable traits become more common in the population, and undesirable traits are eliminated. Genetic knowledge is often used in the process to ensure that the selected traits are inherited.

Types of selective breeding

1. Line Breeding

   Involves breeding organisms that are closely related (e.g., a cow with a relative bull) to reinforce desirable traits within the gene pool.

   Example: If a cow has desirable traits, it may be bred with a bull that shares similar qualities.

   1. Human equivalent: Line breeding in humans is similar to mating relatives who are one-step removed (like first cousins).
   2. Goal: To concentrate desirable traits and maintain a pure line of characteristics.

2. Inbreeding

   Involves mating closely related organisms, such as parents with offspring, in an attempt to retain desirable traits in the next generation.

   This method can intensify both desirable and undesirable traits, and it may lead to genetic problems or weaknesses.

   Drawback: The close genetic relationship can amplify genetic defects or undesirable recessive traits.

3. Outcrossing (Outbreeding)

   Involves mating organisms that are not closely related, typically with no shared ancestors for several generations.

   This method introduces genetic diversity and can reduce the concentration of undesirable genes from inbreeding.

   Benefit: It is generally preferred over inbreeding and line breeding as it helps avoid the negative effects of genetic defects.

Charles Darwin and artificial selection

• Darwin's Use of the Term

  Darwin used the term artificial selection in contrast to natural selection. In artificial selection, humans intentionally breed organisms with certain traits, while in natural selection, organisms with traits that improve survival or reproduction are more likely to pass on their genes in the wild.

• Implication for Evolution

  Through selective breeding, humans can create new varieties and even species over time. This is evidence that new species can arise from pre-existing species through the gradual accumulation of changes, which aligns with Darwin's theory of evolution.