*in the most scientific nerdy voice possible*
For fertilization to be accomplished, a mature human male sperm and a mature human female egg are needed. Before fertilization, each has only 23 chromosomes. They each possess "human life," since they are parts of a living human being; but they are not each whole living human beings themselves. They each have only 23 chromosomes, not 46 chromosomes—the number of chromosomes necessary and characteristic for a single individual member of the human species. Furthermore, a sperm can produce only "sperm" proteins and enzymes; an egg can produce only "egg" proteins and enzymes; neither alone is or can produce a human being with 46 chromosomes.
The fusion of the sperm (with 23 chromosomes) and the egg (with 23 chromosomes) at fertilization results in a live human being, a single-cell human zygote, with 46 chromosomes—the number of chromosomes characteristic of an individual member of the human species. Zygote: A zygote is the beginning of a new human being (i.e., an embryo).
This new single-cell human being immediately produces specifically human proteins and enzymes (not carrot or frog enzymes and proteins), and genetically directs his/her own growth and development. (In fact, this genetic growth and development has been proven not to be directed by the mother.) Finally, this new human being—the single-cell human embryo—is biologically an individual, a living organism—an individual member of the human species.
The human embryonic organism formed at fertilization is a whole human being, and therefore it is not just a "blob" or a "bunch of cells." This new human individual also has a mixture of both the mother’s and the father’s chromosomes, and therefore it is not just a "piece of the mother’s tissues".
Some people may say that the embyro is only a "potential human". Scientifically there is absolutely no question whatsoever that the immediate product of fertilization is a newly existing human being. A human embryo is a human being. It is not a "potential" or a "possible" human being. It’s an actual human being—with the potential to grow bigger and develop its capacities.
Some may say that the embryo is neither a boy nor a girl at conception. The immediate product of fertilization is genetically already a girl or a boy—determined by the kind of sperm that fertilizes the egg at the time of fertilization.
That concludes todays lesson in sex/health education today.