If a dna molecule is compared to a spirtual staircase, what parts make up steps?

What molecules will be best used to compare different species with the exact same sequence of amino acids? why would two species have the same protein even if the molecules in question is different? (hint: transcription to translation to protein).

The picture represents a structure of the respiratory system. which is the function of this structure? to bring air into the body to exchange oxygen with carbon dioxide to carry air to the lungs to release oxygen from the body

At which point is crust neither created nor destroyed? island chain mid-ocean ridge divergent boundary transform boundary