To select and retain the desirable trait of large body size which a farmer has observed in his herd, the farmer needs to

To select and retain the desirable trait of large body size which a farmer has observed in his herd, the farmer needs to inbreed the animals in his herd. Inbreeding refers to the breeding of closely related animals. By mating closely related animals, the farmer increases the likelihood of offspring inheriting desirable traits, such as large body size, from both parents. Over time, the frequency of the desired genes will increase in the population, leading to more animals with the desirable trait. However, inbreeding can also increase the frequency of harmful recessive genes, which can lead to health problems in the offspring. Therefore, careful selection of animals for breeding is necessary to avoid harmful effects of inbreeding.