Abortion - Moments of (Mis)Conception

The 'Limits on Abortion' thread was ended for going off topic.However there does seem to be an appetite for the wider discussion on this topic which I for one am interested in hearing.As such I would like to ask the following specific questions -1) Biologically is there a 'moment' or 'point' at which something non-human becomes something human?
2) Biologically (in the context of human development) is there a point at which something non-living becomes something living?
3) Does the argument put forward by opponents of abortion rely on defining such 'moments', 'points' or 'instantaneous boundaries' between that which should be considered human life and that which should not??The obvious answer to 1) would seem to be the 'moment' of conception. However my limited understanding of biology is that there is no such 'moment' and that, like most biological processes, this is a graduated process. Can anyone confirm or refute this on firm biological grounds??If there is no 'moment' does that mean that any decision regards abortion is therefore as arbitrary as (for example) legally classifying someone of 18 years old as an adult, with all the priveliges and responsibilities that entails, but classifying a person of 17 years and 364 days as a child in the eyes of the law???What exactly is the difference between this sort of arbitrary legal classificatiion and the decision as to what is a human life and what is not in terms of abortion?
Is there a firm firm biological premise on which the boundary between what is a human life and what is not available, or is the decision effectively as arbitrary as defining adulthood???

Well I agree but when opponents to abortion rationalise their views it seem to be almost always in terms of this life/non-life, human/non-human barrier.Presumably if there is a belief in the soul it is also at this same point/moment/barreir that this supposedly manifests itself.This is why I am interested to know whether or not such a definite biological point actually exists and if it does not what effect this has on the rationalisation of their views.

But when exactly is conception??As I understand it conception itself is a process that takes a couple of days to complete. More than one sperm can pass through the outer barreier of the egg and it takes a period of time to eject those that are not the final one that will be used to combine DNA. The process of the egg and sperm combining itself takes time and then the genome is not in control of he cell for sometime after that. In total a graduated process lasting a couple of days.As far as I can see any choice as regards what is a human life and what is not is made purely arbitrarily depending on what view of abortion one wishes to rationalise.If we accept that any decision as to what is a human life and what is not is purely arbitrary (in the sense that a number of totally opposing points of view can be equally well rationalised by means of biology) then maybe the whole argument can move on from trying to answer this in terms of science and move on to trying to answer this in terms of the more answerable questions such as those relating to the effect on the mother, society etc. etc.