Dog breeding is the practice of mating

Mating

In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

 selected specimens with the intent to maintain or produce specific qualities and characteristics.

Dogs reproduce without human interference, so their offsprings' characteristics are determined by natural selection

Natural selection

Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

. Domestic dogs may be intentionally bred by their owners.
A person who intentionally mates dogs to produce puppies is referred to as a dog breeder

Breeder

A breeder is a person who practices the vocation of mating carefully selected specimens of the same breed to reproduce specific, consistently replicable qualities and characteristics....

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