It takes a passionate look at the evolution of sex, which allows a species to pass its genes along from generation to generation.
Sex is everywhere.
In its simplest form, sex is the process of mixing genes from two parents into a new offspring. This gene swapping ensures that each generation is just a bit different from the one that came before, and that each individual is a bit different from others. This variation gives the species a better chance of surviving changing conditions. A few individuals, for instance, might be able to survive a deadly new virus and carry on the species, while the rest die. Eventually, the virus-resistant newcomers might even evolve into a new species.