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17.5 Artificial selection - Coggle Diagram
17.5 Artificial selection
The process by which humans select organisms with desired traits to survive and reproduce
Steps
Population has variation
Breeder selects two individuals that exhibit desired characteristics and are compatible
Chosen two individuals are bred together
Offspring are grown to adulthood and those with the most desired characteristics are selected
Process is repeated over generations until all individuals exhibit desired characteristics
Introduction of disease resistance
Plants are screened for resistance and artificially selected
Wheat is bred for resistance to head blight (caused by
Fusarium
fungus)
Rice is bred for resistance to rice blast (caused by
magnaporthe
fungus)
Results in increased yield
Inbreeding and hybridisation
Inbreeding increases homozygosity (the more related the parents are, the more alleles they share, and therefore the more likely the offspring are to have the same/duplicate alleles)
Inbreeding depression is when repeated inbreeding causes homozygosity and therefore expression of harmful recessive alleles
Outbreeding produces more heterozygous plants that express fewer harmful recessive alleles (hybrid vigour)
Improving milk yield of dairy cattle
Humans select for cows with high milk yield
However, when artificial selection is no longer applied, average milk yield decreases over generations, indicating that it is a disadvantageous trait at this extreme
Cows with high milk yield are more vulnerable to inflammation and lameness