CK-12 Foundation
Ck 12: Life Science: Fertilization
[Free Registration/Login may be required to access all resource tools.] The sperm and egg don't look anything like a human baby. After they come together, they will develop into a human being. How does a single cell become a complex...
CK-12 Foundation
Ck 12: Biology: Fetal Development and the Placenta
[Free Registration/Login may be required to access all resource tools.] Discusses the role of the placenta during fetal development.