A plant life cycle diagram shows a sporophyte plant create a spore that grows into a gametophyte plant that releases gametes, which then combines with another gamete to form the embryo of another sporophyte plant. The exact details of these different stages vary greatly between groups of plants.
In any group of plants, the sporophyte has two versions of each chromosome in its DNA, whereas the gametophyte has only one. This transition between gametophyte and sporophyte generations is known as the alternation of generations, which all plants share.
In mosses, the gametophyte is the larger generation, and the sporophyte grows as a much smaller and dependent organism on it. In ferns and their relatives, the sporophyte generation is larger, but both the sporophyte and gametophyte generations live independently of one another. In both ferns and mosses, sperm generated by gametophytes must swim through water to get to the egg in another gametophyte.
In higher plants, such as flowering plants, the sporophyte is very dominant and gametophyte is tiny, made up of only a few cells. These are totally dependent on the sporophyte generation. Their gametes are not dependent on water to reach one another. Instead, these plants use animals or wind to carry male gametes to the female gametes.