What is a zygote?

A zygote is defined as the first cell that is formed when a sperm cell successfully fertilizes an egg cell. This process of fertilization involves the merging of genetic material from both the male and female gametes, resulting in a single diploid cell that contains a complete set of chromosomes—half contributed by the sperm and half from the egg. The zygote then undergoes a series of cell divisions, leading to the development of an embryo. This is a fundamental concept in human reproduction, as the zygote marks the very beginning of the developmental process that can lead to the formation of a new organism.

The incorrect options represent different biological concepts unrelated to the definition of a zygote. The mention of a small egg cell relates to an oocyte rather than a zygote. The fluid surrounding the fetus refers to amniotic fluid, which serves a different physiological role during pregnancy. A type of reproductive hormone does not define a zygote either; hormones are involved in various reproductive processes, but they are not the cells that arise from fertilization.