SELECTIVE BREEDING

Four examples of selective breeding that I need to be able to describe+

1)domestic dogs have been selectively bred to have a gentle nature

2) food crops such as wheat have been selectively bred to be resistant to disease

3) animals such as cows have been selectively bred to produce more meat or milk.

4) certain plants have been selectively bred to produce large or unusual flowers.

How selective breeding is carried out

Example= Imagine we wanted to breed large cows for meat. First take a mixed population of cows and select the largest male and female. When then breed these together. Sexual reproduction produces variation in the offspring. So offspring will be a mixture of larger animals and smaller animals. We then select the largest male and female offspring and breed these together. Then continue doing this over many generations until the offspring are large.

one big problem with selective breeding

If we breed together closely related animals or plants then we can get inbreeding.

Inbreeding can cause some breeds to be prone to disease or inherited defects.

Dog breeds have been selectively bred for hundreds of generations. Many dog breeds develop inherited disorders such as joint problems, heart disease or epilepsy.