A human may go from being microscopic to being six feet tall in less than 16 years. What change on the cellular level accounts for most of the change in size?

A.

the shape of the cells changes

B.

the number of cells increases

C.

the size of the cells increases

D.

the number of different kinds of cells increases

Correct answer is B.

Explanation:

In their nucleus cells contain DNA. The DNA has information about size, shape and function of each cell. When the cell reaches it's full size it stops growing and starts doing whatever it's function is. If more cells are needed then the cell replicates. This explanation excludes answers A and C.

Male and female sexual cells are used to conceive a baby. These cells combine to form a new type of cells. In the first few weeks all types of cells are created. Then the creation of new types of cells stops and existing cells multiply in order to achieve needed number of cells. This explanation excludes answer D.

When we compare an adult person and a baby we can see that, for example, an adult has bigger bones than a baby. This was result of increasing number of existing types of cells without creating any new type.