Roof rats are the worst rodent pest in the state of Florida and most abundant. The Norway rat (Rattus norvegicus) that is familiar to most people is rare in Florida. Roof rats consume and destroy stored animal and human food, attack fruit crops, and take up residence in attics, soffits, hollow walls, and out-buildings.
1 The sperm brings in another 23 chromosomes to complement the 23 held in the egg to get to a total of 46 chromosomes - what all of us normal people have.  We know from in vitro fertilization studies that the egg is only capable of being fertilized for about 24 hours after ovulation.
Fertilization and Embryo Development. Following ovulation, the egg is capable of fertilization for only 12 to 24 hours. 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 thirty hours. Fertilization â sperm union with the egg â occurs in this portion of the tube. The fertilized egg then begins a rapid descent to the uterus.