What happens at conception?
At conception, also known as fertilization, a male sperm unites with a female ovum (egg). The single-celled human organism formed by the fusion of sperm and egg is known as a zygote.
Sources:
Condic, Maureen, Ph.D. “When Does Human Life Begin? A Scientific
Perspective.” The Westchester Institute, October 2008. Accessed October 10,
2013. http://westchesterinstitute.net/images/wi_whitepaper_life_print.pdf.