6 THE HUMAN ORGANISM
6B) HUMAN DEVELOPMENT
Fertilization. By the end of 5th grade, students know that babies result from the fusion of sperm and eggs. However, they often don't understand how the fusion brings new life. Before students have an early understanding of genetics, they may believe that the baby exists in the sperm but requires the egg for food and protection, or that the baby exists in the egg and requires the sperm as trigger to growth (Bernstein & Cowan, 1975; Goldman & Goldman, 1982).
Death. Lower elementary-school children understand that death is irreversible and inevitable (Lazar & Torney-Purta, 1991). They usually think death is caused by an external agent but do not connect death with what happens within the body as a result of these external events (Carey, 1985). Around 3rd or 4th grade, students understand that death means the cessation of bodily functions (Carey, 1985).