Selective breeding

• when humans choose certain animals or plants to breed for their useful characteristics

steps (occurs over many generations)

1. deciding which characteristics are important enough to select

2. choosing parents that show these characteristics from a mixed population

3. breeding the parents together

4. choosing the best offspring with the desired characteristics to produce the next generation

5. repeating the process continuously over many generations until all offspring show the desired characteristics

desired characteristics in plants:

• disease resistance in food crops

• wheat plant that produces lots of grain

• large, unusual flowers

• improve yield

desired characteristics in animals:

• lots of milk/ meat

• large eggs

• gentle nature (dogs)

disadvantages:

• reduces gene pool → inbreeding reduces no of different alleles

• inbreeding → health problems → larger chance of inheriting harmful genetic defects (limited gene pool)

• big problems if new disease → not much variation: kills one kills all

selective breeding → reduction in the the number of different genes → less chance of any resistant alleles being present in population