Classifying things by observation can best be done by using a dichotomy wedge key taxon

Classifying things by observation can best be done by using a  : Taxon

Taxon divided organisms into different groups based on their unique similarities, and these similarities can be recognized by observing parts and behavior of the organisms. For example, Organisms generally divided into two groups. Those who have a backbone (vertebrata,  such as mammals and reptiles ) and those who don't have backbones (such as arthropoda)

This is the best way to classifying the organisms because the similarities between them do not exist in their backbones alone. This give more room/possibilities for the classification. For example, The organisms could also be classified by other similarities (such as how they obtain food, their body structure, how they reproduce, etc)

carbohydrates are the body's preferred source of energy.

ya the other dude is right