Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: There are creatures which, depending on species, have varying numbers of body parts. Arachnids have a certain number, while humans have a different number, and these numerous parts can be attributed to
inherited characteristics
evolutionary development.