There are two types of artificial selection: mass and individual. During mass selection, a group of individuals with the desired traits is isolated. The offspring with this selection is genetically heterogeneous and therefore gives a splitting of characters during reproduction. In this regard, the selection is carried out in a number of generations.
During individual selection, isolated individuals with valuable qualities are isolated and their offspring are separately grown. With subsequent self-pollination in plants or closely related crosses in animals, clean lines are drawn. The clean line is a group of genetically homogeneous (homozygous) organisms that represent valuable source material for selection
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.