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Selective breeding

Selective breeding is the traditional method for improving crops and livestock, such as increasing disease resistance or milk yield.

New varieties

Natural selection and selective breeding can both cause changes in animals and plants. The difference between the two is that natural selection happens naturally, but selective breeding only occurs when humans intervene. For this reason selective breeding is sometimes called artificial selection.

Different varieties of plants and animals with desired characteristics can be developed by selective breeding. For example:

  • cows that produce lots of milk
  • chickens that produce large eggs
  • wheat plants that produce lots of grain

The new varieties may be economically important. For example, they may provide more or better quality food to feed people.

Aberdeen Angus bull
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Example of selective breeding

The Aberdeen Angus bull is bred for beef

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Main steps involved

Selective breeding takes place over many generations. These are the main steps involved:

  1. decide which characteristics are important enough to select
  2. choose parents that show these characteristics
  3. choose the best offspring from parents to produce the next generation
  4. repeat the process continuously
A picture of different breeds of dogs including poodle and golden retriever

All these breeds of dog are the results of selective breeding from a common ancestor

Problems with selective breeding

Future generations of selectively bred plants and animals will all share very similar genes. This could make some diseases more dangerous as all the organisms would be affected. Also, there is an increased risk of genetic disease caused by recessive alleles.

All the genes and their different alleles within a population is its gene pool. Inbreeding can lead to the loss of alleles from the gene pool, making it more difficult to produce new varieties in the future.

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Glossary
  1. alleles Different forms of the same gene.
  2. antibiotics Substance that controls the spread of bacteria in the body by killing them or stopping them reproducing.
  3. bacteria Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium.
  4. evolution The process of change in the inherited traits of a population of organisms from one generation to the next.
  5. gene The basic units of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production.
  6. MRSA Methicillin-resistant Staphylococcus aureus, a strain of bacterium resistant to an important antibiotic.
  7. mutation A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes.
  8. natural selection The natural process whereby the best-adapted individuals survive longer, have more offspring and thereby spread their characteristics through a population. Sometimes known as 'survival of the fittest'.
  9. recessive allele Alternative form of a gene that is expressed only if a dominant allele of that gene is not present. An organism must have two copies of a recessive allele for that allele to be expressed.
  10. selective breeding An artificial process in which organisms with desired characteristics are chosen as parents for the next generation.
  11. species Used in the classification of living organisms, referring to related organisms capable of interbreeding.
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