Mammals evolved into larger organisms and began subdividing into various species in the a. mesozoic era c. cenozoic era b. paleozoic era d. devonian era

The answer is C. Cenozoic era. 
It's the era when mammals evolved into larger organisms and began subdividing into various species. Cenozoic is also known as the age of mammals, because it's the mammals that mostly occupied the lands.

I agree with the first answer

Mitochondria is the cell organelle that produced the energy that is needed in the body system in form of atp, that is why it is called the power house of the cell. energy is needed by the living organisms to carry out the activities which sustain life.  if the mitochondria is destroyed atp will not be produced. if the mitochondria is destroyed, energy production will stop and the affected living organism will not have the energy to carry out the necessary life processes; this will lead to the death of the organism.