However, there are instances of genetic mutation that can be beneficial to the survival of an organism. In this way, beneficial traits are passed on. Those traits are 'selected' by nature as being more effective for the conditions. The original variety of the species may or may not continue to survive. Even in the absence of selective pressures, genetic sampling errors in small populations can bring about physical change.
Evolution is 'descent with modification'.
Explore this page thouroughly before coming to a decision. This also includes links to other topics, like the Second Law of Thermodynamics, the Origin of Life, and more. Links to the Talk.