Following fertilization, cell division produces a small cluster of cells
that then differentiate by appearance and function to form the basic tissues
of an embryo. During the first three months of pregnancy, organs begin
to form. During the second three months, all organs and body features develop.
During the last three months, the organs and features mature enough to
function well after birth. Patterns of human development are similar to
those of other vertebrates.
| NSES Content Standard C
Life Science: The cell Grades 9-12, page 184 Cells can differentiate, and complex multicellular organisms are formed as a highly organized arrangement of differentiated cells. In the development of these multicellular organisms, the progeny from a single cell form an embryo in which the cells multiply and differentiate to form the many specialized cells, tissues and organs that comprise the final organism. This differentiation is regulated through the expression of different genes. |