@KomatiiteBIF
Let's talk about what life is first before we go on to discuss the various types of life and their values.
Sounds to me like you're still running with the cookie baking analogy. As if the new embryo is a blob of tissue or 'dough' that is being mixed and formed by other forces.
But "who" is making the cookie? "Who" is following the recipe? That would have to be the agent that has those instructions. Does the mother or her womb have those instructions? What about species such as some fish whose eggs fertilize externally? No, the instructions are the DNA in the embryo itself. The embryo is a newly formed agent which is proactively developing itself as described in the definition of life.
All forms of life have dependencies. None of us can truly sustain ourselves with nothing from outside. We all need to eat and in many cases also need some kind of protection from the elements in order to survive. We all make the effort to procure our food and resources from our surrounding environment, at all stages of growth and development from fertilization to birth to death. God gives food to all creatures in its season, we do well to know Who supplies our daily bread.
But the embryo has different DNA, different instructions than its parents individually, therefore it is new, and its holding and using of its own instructions means it is life - ergo, new life. Life is life, and it begins at conception, whatever species that life may be.