Final answer:
The black, sticky stuff in the diaper is called meconium, which is the baby's first stool.
Step-by-step explanation:
The black, sticky stuff in the diaper of the father's 1-day-old daughter is called meconium. Meconium is a normal substance that is the baby's first stool. It is a tarry, greenish-black substance that accumulates in the fetal intestines during the second half of gestation. Typically, a newborn's first stools consist almost entirely of meconium, but they later transition to seedy yellow stools or slightly formed tan stools as meconium is cleared and replaced with digested breast milk or formula.