1. 39.4 Fertilization and Development

2. Zygote Fertilized Egg.

3. Implantation Process in which a blastocyst attaches itself to the wall of the uterus.

4. Differentiation Process in which cells become specialized in structure and function.

5. Gastrulation Process of cell migration by which a third layer of cells is formed within the cavity of a blastocyst.

6. Neurulation Development of the nervous system.

7. Placenta Organ in placental mammals through which nutrients, oxygen, carbon dioxide, and wastes are exchanged between embryo and mother.

8. Fetus Name given to a human embryo after eight weeks of development.

9. Key Concept The process of a sperm joining an egg is called fertilization.

10. Key Concept The stages of early development include implantation, gastrulation, and neurulation.

11. Key Concept The placenta is the embryo’s organ of respiration, nourishment, and excretion.