Answer: Sexual Reproduction.
Step-by-step explanation: The process that provides variation to the species is sexual reproduction. The sperm and the eggs that fuse together to form zygote can have multiple combinations of chromosomes.
These different combinations provide variation in the species. These variation are the foundation of natural selection. The fittest organism survive and reproduce and the unfit organism does not survive.
Example: Different fur color of rabbits (white, light brown, dark brown).