This illustration from an old textbook shows some of the over 150 different dog breeds that can be seen around the world today. how do you think all of these different breeds were developed?

Dog breeds were developed through artificial selection.

Explanation:

Artificial selection is the process of crossbreeding conducted by the human being in order to select desirable characteristics in animals (and plants). It was through this process that humans were able to develop many dog breeds.

Breed dogs were developed by crossing parents and children, grandparents and grandchildren, siblings and dogs of the same family that had similar characteristics, in order to keep them and make the dog “cute” and pleasant to the taste of those who developed. This can develop very beautiful breeds, however, unfortunately, these crosses also brought problems for many of these animals.