The change in size of the bone marrow (where blood cells are produced) as an infant matures is an example of whereas the transformation of blood stem cells into white blood cells is an example of

growth, differentiation

Growth is a phenomena which results in the increase in size and shape of the organism with respect to the increase in number of cells and size of cell that makes up an individual. Differentiation is a property of cell to increasing grow in number and transform into a form having a specialized function.

The change in size of the bone marrow (where blood cells are produced) as an infant matures is an example of growth:

The size of the bone marrow will increase in an infant with age as bone marrow is responsible to produce white blood cells, which are important for immunity. So, as to make infant immune with age.

The transformation of blood stem cells into white blood cells is an example of differentiation:

In this case the differentiation of blood stem cells will lead to the formation of white blood cells, which have a specialized function in the body that is providing immunity against foreign agents like pathogens.

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