Yes, this is true, and it is actually one of the organisms driving evolution! Some organisms develop mutations that are actually beneficial (better eye-sight, for example) and they're more likely to pass those to their children that individuals without those mutations!
The last one
some cells are living and some cells are not
i think
I would say the alveoli. They are tiny air pockets in the lungs: this is where the diffusion of oxygen and carbon dioxide occurs.
Hope this helps! x
