zygots

A zygote is the initial cell formed when two gametes (sex cells), a sperm and an egg, fuse during sexual reproduction. This fusion, known as fertilization, results in a single diploid cell that contains the complete set of chromosomes from both parents. The genetic material from the sperm and egg combines to form a unique genetic blueprint for the future organism.

Immediately after fertilization, the zygote undergoes a series of rapid cell divisions called cleavage. These divisions are mitotic, meaning that each new cell, called a blastomere, is genetically identical to the original zygote. The zygote begins as a single cell and progresses through stages like the two-cell stage, four-cell stage, and so on, forming a morula, which is a solid ball of cells.

As development continues, the morula develops into a blastocyst, a hollow ball of cells with an inner cell mass that will eventually give rise to the embryo. The zygote's journey is the very beginning of embryonic development, and its successful formation and subsequent division are critical for the continuation of a species. The zygote is the foundational unit from which all the cells and tissues of a new individual will develop.