Choose characteristics for dichotomous keys.
Similarities are due to?
dichotomous keys group similar organisms together and choose characteristics which group them to reflect similarity
Is there software for Dichotomous keys?
Biology - Choosing characteristics for dichotomous keys
Choosing characteristics for dichotomous keys
Dichotomous keys group similar organisms  together.
When designing keys of organisms, biologists try to select characteristics
 that group the organisms in a way that reflects their overall
For example, if you were classifying animals it might be tempting to
divide them into two groups using their ability to fly or not. Within the
flying group you would have insects and bats.
However, when you consider all their characteristics, bats have far less
in common with insects than they do with many non-flying animals such as
humans. Therefore, bats would be better placed in the same group as humans
than with insects.