First of all, when an organism reproduces asexually, that organism creates a genetically similar or identical copy of itself without a contribution of genetic material from another individual. For example, I would assume that the reproduction of fish is asexually. I say this because the female fish lay her ovules in the water then the male sprays them with his sperms; therefore; there are no sexual mating occurring between the male or female. On the other hand, there are evolutionary advantages that come with organisms reproducing sexually. Sexual production produces genetic diversity within an organism which reduces the chance of passing on genetic disorders. Also, it creates the ability to produce variable offspring, some of which will have improved chances of survival in changing environments
Secondly, three ways that sexual reproduction increase genetic variability includes the independent orientation of chromosomes during meiosis, crossing over during meiosis and the random fertilization. During the independent orientation and the crossing over, the genetic information gets mixed up which increases genetic diversity among the offspring. Because of both the independent orientation and the crossing over, male animals can possibly produce millions or hundreds of millions of genetically unique sperm and because of that; siblings, except for identical twins, never have exactly the same genetic information.
Lastly, two prezygotic isolating mechanisms that prevent hybridization between two species include behavioral