AP BIOLOGY

Detailed explanation-1: -During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst . The blastocyst then burrows into the uterine lining-a process called implantation.

Detailed explanation-2: -Contact between the egg and sperm is random. Once the egg arrives at a specific portion of the tube, called the ampullar-isthmic junction, it rests for another 30 hours. Fertilization-sperm union with the egg-occurs in this portion of the tube. The fertilized egg then begins a rapid descent to the uterus.

Detailed explanation-3: -Fertilization by a sperm activates the ovum, which takes place in the distal third of the fallopian tube. Once the sperm has entered the ovum, immediate changes take place not to allow further penetration of the ovum. These exact changes are in the biochemical section of this article.