We breathe in air, not straight oxygen. Attached is a pie chart showing roughly what percentage of what is in the air we breathe
DNA is an acid that contains resources needed for development and function of every living thing, EVERY LIVING THING. even bacteria and viruses have DNA. without DNA there would be no life.
The best phrase is 'natural selection is a process that causes evolution '. Natural selection can also be referred to as selection pressures within a population that favour particular traits that enable the population to better adapt to its habitat. It's could be better camouflage, high sense of smell, and etcetera. These traits are preserved while those that cause disadvantage are diminished. This causes evolution of the population .
