What makes it morally permissible to destroy a baby, but wrong to kill an adult? What properties must something have to be a person, i.e., to have a serious right to life?

What makes it morally permissible to destroy a baby, but wrong to kill an
adult? What properties must something have to be a person, i.e., to have a serious right to life?

At what point in the development of a member of the species
Homo sapiens does the organism possess the properties
that make it a person?

Does this conceptual truth follow from
the above analysis of the concept of a right?