Oplodnní

Oplodnění, or fertilization, is the biological process by which male and female gametes unite to form a zygote, the first cell of a new individual. It combines paternal and maternal genetic material and initiates embryonic development. Fertilization also triggers cellular and developmental events that switch from gamete to embryo.

In animals, fertilization can be internal or external. Sperm encounters and binds to the egg, often after navigating protective layers. The acrosome reaction allows the sperm to penetrate barriers, and the membranes of the sperm and egg fuse. The genetic material from the two gametes then merges to form a diploid zygote. Mechanisms such as cortical reactions help prevent polyspermy, ensuring only one sperm contributes to the zygote. After fusion, the zygote begins a series of cell divisions (cleavage) that lead to embryo formation.

In plants, fertilization typically involves pollen delivering sperm cells to the ovule. In angiosperms, one sperm fertilizes the egg to form a zygote, while a second sperm fuses with two polar nuclei to form the triploid endosperm, which nourishes the developing embryo. This process is known as double fertilization. Gymnosperms have a simpler fertilization culminating in the formation of a zygote without the endosperm development seen in angiosperms.

Fertilization is a central step in reproduction and has been studied across many species. It is also a focus of assisted reproductive technologies, such as in vitro fertilization, which enable fertilization outside the body under clinical supervision.