I was thinking about this, and there seems to me to be a difference between a fertilized egg and one that isn't or a sperm. The reason is this, a sperm has about a one in one million chance of fertilizing an egg, right? Also, a sperm only carries half of the human chromosones. Same thing for an egg -- I'm not sure what the chances are of an egg becoming fertilized, but when you put that together with the chances of a sperm fertilizing an egg, you have a less than one in a million chance of a certain egg combining with a certain sperm.
Now, if you consider a fertilized egg, you will see that it is already a special entity, because it somehow beat the odds (even though there are millions of sperm in each ejaculation and there are several eggs available -- not every act of sexual intercourse results in pregnancy anyway). Aside from that, a fretilized egg can arguably be considered a human. For example, it already has all of the DNA encoding that it requires and will ever have throughout its lifetime. That means that height, weight, body type, build, intelligence, personality, sex, race, etc. are all there from the moment of conception. It just doesn't look human yet. However, it is certainly not a frog or a moth. On the point of looking human, would you consider someone so disfigured that he didn't look human anymore to not be human?