Final answer:
Infants undergo rapid physical changes in the first year, doubling in length and tripling in weight. The principles of physical growth during infancy include rapid growth and a sequential pattern. Teething and the development of deciduous teeth typically begin around six months.
Step-by-step explanation:
During the first year, an infant goes through rapid physical changes. They double in length and triple in weight, with the head and trunk growing most rapidly.
The two basic principles of physical growth during this time are that growth is most rapid during infancy and that it occurs in a sequential pattern.
At around six months, the deciduous teeth start to emerge, a process known as teething. Typically, all upper and lower incisors will emerge during the first year. In terms of weight and length, a healthy, well-nourished infant will generally triple their birth weight and double their birth length by their first birthday.