Fertilization is when a sperm and egg combine to form a zygote, a diploid cell, which divides and transforms into a blastocyst for implantation. Occasionally, two eggs can be fertilized resulting in fraternal twins. Implantation marks the start of pregnancy as the embryo attaches to the uterus lining.
Fertilization is the process where a haploid sperm and a haploid egg cell merge to form a zygote, which is a single diploid cell. This typically occurs in the Fallopian tube. The zygote then undergoes a series of cell divisions called cleavage, resulting in a structure known as the morula.
As development proceeds, the morula transforms into a blastocyst, which is a differentiated, fluid-filled ball of cells that eventually implants into the uterus lining. Double fertilization can occur in some plants, where one sperm cell combines with the egg to create the zygote, and another fuses with the polar nuclei to form the endosperm.
During ovulation, generally only one egg is released, though sometimes two can be fertilized, resulting in fraternal twins which are not more identical than siblings born at different times. Implantation is when the developing embryo fixes itself to the side of the uterus, marking the beginning of a potential pregnancy.