<em>Biological evolution is defined as the formation of complex organisms from single ancestral type over a large time period. Evolution believes that all living organisms descended from a common ancestor but not without modification.</em>
There are several evidence to support the theory of evolution including morphological evidence, paleontological evidence, biochemical evidence, among others.
The similarity in the structure and components of DNA of all living organisms is one of the evidence pointing to the fact that living organisms might truly have been from a common ancestor. In addition, all living organisms tend to use ATP largely as their source of energy, giving further credence to evolution theory.
The second one changes in the amount of atmospheric gases because it think it might effect everyone including plants and animals because will all breath the same air rather than a mountain building it might affect the animals that like there.