What is the most important reason to control the conditions of a experiment ?

Ifound this on google “aristotle (384–322 bc) in western scientific taxonomy the greek philosopher aristotle was the first to classify all living things, and some of his groups are still used today, like the vertebrates and invertebrates, which he called animals with blood and without blood.” i hope this you for what your looking for.

Ithink the dna sequences may vary but the amino acid sequences are identical.