13.3 Selective breeding

Question 1

Selective breeding (artificial selection) def

Answer 1

The process by which humans breed plants and animals for particular genetic characteristics

Question 2

For how long have humans been selectively breeding

Answer 2

For thousands of years since they first bred food crops from wild plants and domesticated animals

Question 3

How does selective breeding work

Answer 3

• parents with the desired characteristic are chosen from a mixed population
• they are bred together
• from the offspring those with the desired characteristic are bred together
• this continues over many generations until all the offspring show the desired characteristic

Question 4

Examples of characteristics for which humans have done selective breeding (for usefulness or appearance)

Answer 4

• disease resistance in food crops
• animals which produce more meat or milk
• domestic dogs with a gentle nature
• large or unusual flowers

Question 5

What is a negative effect of selective breeding

Answer 5

Could lead to inbreeding where some breeds are particularly prone to disease or inherited defects

Question 6

What is another limitation of selective breeding

Answer 6

• it greatly reduces the number of alleles in the population
• this reduces variation in the alleles for a given characteristic
• if the climate changes or a new disease emerges, none of the animals or plants in the population can cope with the change
• this can result in the population dying out