Mutation refers to the change in the DNA of organisms. Mutations may occur upon exposure of individuals to certain mutagens, such as UV radiations, present in environment. Any error during DNA replication also leads to change in the DNA and mutations. Mutations add variations and increase the genetic diversity of the population. Mutations may be beneficial or harmful.
The answer is asexual reproduction. This type of reproduction does not involve fusion of gametes. The offspring arise from a single organism and inherit the genes of that parent only. Consequently, there is little variation from parent compared to sexual reproduction.