Understandings:

• Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation
• Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm
• Fertilization in animals can be internal or external
• Fertilization involves mechanisms that prevent polyspermy
• Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy
• hCG stimulates the ovary to secrete progesterone during early pregnancy
• The placenta facilitates the exchange of materials between the mother and fetus
• Estrogen and progesterone are secreted by the placenta once it has formed
• Birth is mediated by positive feedback involving estrogen and oxytocin