Hi. In this video we'll be talking about the specifics of animal development. Now, development begins with fertilization, which is the proverbial fusion of sperm and egg to form a zygote. This occurs in the fallopian tube and the egg is actually swept into the tube. Bythe cilia fertilization actually has a very short window in which it can occur. It has to occur within 24 hours of ovulation, which is the rupturing of the Corpus Ludie, Um, and releasing of the, uh, EG. Now, when the sperm and egg actually get together, you have a special reaction occur. You see, the sperm has this tip scene right here called the Ark A zone. And the ark is, um, contains these special enzymes that break down the protective coat around the egg so the sperm fuses with the egg releases those ARCA zones which allow it thio actually get through the egg and, uh, also signal the egg to not let any more sperm in. And this is accomplished by something called the cortical reaction, which releases a bunch of calcium which deep polarizes the membrane, causing a change in membrane potential. And this basically signals the completion of the second biotic division of the egg. All of that is to say that the sperm and egg fuse and there's a bunch of stuff that happens. And it prevents multiple sperm from fusing with the egg and also allows thes sperm and egg form the zygote and begin development. All right, let's flip the page.