Final answer:
Sexual reproduction creates the most variation within a species due to genetic recombination, fertilization, and meiosis, resulting in unique genetic combinations in offspring. Mutation adds randomness to genetic variation, but the evolutionary process is not purely random.
Step-by-step explanation:
The process that produces the most variation within a species is sexual reproduction. Sexual reproduction, through mechanisms such as genetic recombination, meiosis, and fertilization, combines the genetic material of two parents to create offspring with unique genetic makeups. The process of mutation also contributes to genetic variation but is random. On the other hand, sexual reproduction is not entirely random because it involves the selective pairing of gametes. This fact, combined with other processes such as migration and natural selection, indicates that the overall process of evolution is not random, as it results in the non-random accumulation of beneficial traits that aid survival and reproduction.