Here's why:

* Genetic Code: The genetic code, which dictates how codons are translated into amino acids, is nearly universal. This means that a particular codon (like AUG) will code for the same amino acid (Methionine) in bacteria, plants, animals, and even fungi.

* Evolutionary Conservation: The universality of the genetic code is a testament to its ancient origins and its essential role in protein synthesis. Changes to the code would disrupt the production of proteins, which are crucial for life.

Important Note: While the genetic code is largely universal, there are some minor variations found in certain organisms, usually involving the stop codons or the translation of a few codons. These variations are relatively rare and do not fundamentally alter the core principle that codons represent specific amino acids across all life forms.