One Y and one X chromosome.
Answer:
Cephalocaudal
Explanation:
The cephalocaudal principle is known as the general process of physical and motoric development which take place from infancy into toddlerhood and at times at early childhood of which development obeys a head-to-toe progression.
Cephalocaudal is a word that connotes head to toe. Therefore, the cephalocaudal principle is stated as the overall process of development observed in the first set of years in postnatal development majorly with the period from infancy into toddlerhood.
The cephalocaudal principle has to do with both physical and functional development. On the basis of the earliest (i.e., physical development), physical growth in size, weight, and feature differentiation obey this process or form of development. The signs of this is well observed in a contrast of the physical characteristics of an infant In contrast to a toddler. In consideration of the latter, the head is mostly disproportionately big in contrast to the other parts of the body. By the time the preschool years is over for most children, it is well noticed that most must have done away with this top heavy appearance just as seen in our question.
