Cloning is the process used to create an exact genetic copy of an organism while selective breeding is the process used to produce particular characteristics and traits in organisms. Some types of cloning can occur naturally, but selective breeding only occurs when humans intervene.
Cloning happens through asexual reproduction. However, natural clones can occur in humans and other mammals. Identical twins occur when a fertilized egg splits and creates embryos with almost identical DNA.
There are three different types of cloning. Gene cloning creates copies of genes or DNA, therapeutic cloning creates embryonic stem cells, and reproductive cloning creates copies of whole animals.
While cloning only uses asexual reproduction, selective breeding also uses sexual reproduction. The desired characteristics are chosen, and a male and a female who exhibit those characteristics are bred together.
Plant breeders strive to produce plants with desirable characteristics such as high growth rate or resistance to disease. This is done by crossing two members with dominant alleles for particular genes.
Excessive selective breeding can cause the removal of particular genes from the gene pool altogether. Creating organisms exclusively with more desirable genes can cause the less desirable genes to phase out completely. This is not a risk in the cloning process.