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.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.