Early scientists were conflicted about the mechanism by which cells were created, with some scientists holding the viewpoint that cells were spontaneously crystallized in what was known as free cell formation. Robert Remak discovered ways to fix and observe cell membranes in various stages of cell division. These findings led Rudolf Virchow to proclaim in 1855, Omnis cellula e cellula (every cell comes from another cell), thus completing the tenets of cell theory.

All cells come from preexisting cells.

Explanation:

The given paragraph is about cells develop from the preexisting cells. The doubling of the genetic material in the S-phase is the triggering mechanism for cell division. In the process of mitosis the genetic material get reduced. The daughter cells vary by the amount of genetic material they receive. This proves that the new cells form from the pre-existing cells.

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.