A baby enters toddlerhood when he begins to walk -- sometime around the first birthday. As the child leaves infancy, his biological development progresses rapidly. Both the body and brain grow and change during toddlerhood, opening new possibilities for learning and skill development. You can encourage your toddler's biological development by providing age-appropriate toys, a safe environment to explore and many stimulating experiences.
Growth
Your child will continue to grow in weight and length as she enters toddlerhood. Between ages 1 and 2, your toddler will gain between 3 and 5 pounds. At 15 months old, boys are typically about a pound heavier than girls the same age are. The average weight of a 2-year-old is about 27 to 28 pounds and the average height is about 34 inches. Contrasted with infancy, head-circumference growth is much slower in toddlerhood, with only a net 1-inch gain over the second year of life. Physical changes in appearance are more striking, with toddlers losing their chubby baby roundness and becoming thinner and more muscular.
Physical Control
Toddlers' motor skills progress rapidly during the second and third year of life. The legs and arms' large muscles become stronger and the child's control over them improves. Fine motor skills also improve, giving your toddler more control over grasping and manipulating objects. Motor control develops downward, so the child gains control over the head, neck and torso before the legs and feet. It also develops outward, so control over the arms and legs occurs before control over the fingers and toes.
Brain Growth
Along with the development of a toddler's body comes the development of his brain. New neuronal connections form and unnecessary ones are pruned away. This allows him to develop motor, language, social and cognitive skills. It also removes the brain connections responsible for some reflexes present in babies.
Considerations
While your toddler's biological development will generally proceed in the same fashion as other toddlers, specific milestones might be different between children. For example, some toddlers walk before talking and others concentrate on speech first. General progression of skills is more important than which specific skill comes first or the exact month at which your toddler reaches a given milestone. Culture, health and environment have a significant impact on your toddler's biological development -- much more so than these factors affected her during the first year of life.
