Is the pro-life position really about whether "life" begins at conception or not?

A lot of pro-life arguments claim to be based on the biological evidence that "life" (of some sort) begins at conception. Yet while this may in fact be true, it's apparent from a biological standpoint that a fetus is a very crude form of life (it's not the same as a fully developed human at that point in time), at least as crude, if not more so, than the life of an animal... say a dog or a dolphin or a deer, whatever... (but at least the animals typically have personalities and family, and a will to live)... and yet not many people blink when the "life" of an animal is prevented or taken away. So doesn't this point to the pro-life argument being more about emotion (people who have seen babies born and then grow up and live fulfilling lives as fully developed humans), and about religion/tradition... more than it really has to do with being about a "life." Is the pro-life argument that a fetus is a "life" a valid reason to protect a fetus when we kill other more complex forms of life all the time?