In DNA, the "rungs" between the two strands of DNA are formed from the nitrogenous bases adenine, thymine, guanine and cytosine
According to a source the answer is <span><u>Cyanobacteria were the first organisms to produce oxygen in water, which then escaped into the atmosphere.</u>
These cyanobacteria species were the first ones to "produce" oxygen as a by-product of the photosynthetic mechanisms which enables organisms to make their own food. </span>
Answer:
Cell, Tissue, Organ, Organ System
Explanation:
Protease is used to digest proteins