Birds mitochondrion – ultimate life-form or “clock-bomb”?

Birds are one of the most numerous classes of vertebrates. They have achieved such diversity and distribution largely due to their ability to fly, which consumes a huge amount of energy produced in the mitochondrion. Due to their intensive work, mitochondrial DNA (mtDNA) undergoes a large number of mutations, the key of which is the replacement of adenine with guanine (A>G). These mutations work like a ticking time bomb. The more of them there are, the more difficult it is for mitochondria to work. And if there is an excess, the work stops altogether. Therefore, the mitochondria of birds need to constantly evolve, become the ultimate life form in order to preserve the modern species diversity of birds and not bring them down to earth.