Fertilization

Target Language or Knowledge:

The development and the birth of a baby follow a process that begins with fertilization. Fertilization is the joining of an ovum and a sperm to make a single cell. Fertilization occurs when one_sperm enters the ovum. The remaining sperm break up. A developing baby is called an embryo from the time of fertilization until eight weeks old. From eight weeks old until birth, a developing baby is called a fetus. At the time fertilization occurs, the fertilized ovum is no bigger than the_head_of_a_straight_pin. The fertilized ovum divides_millions_of_times to become a fully developed baby. The fertilized ovum needs a place to grow and develop so it moves through the fallopian_tube and into the uterus. The uterus is an organ that supports a fertilized ovum during pregnancy. A woman's uterus is very muscular and it expands as the developing baby grows.