Now let's see how the general plant life cycle is similar to the human life cycle. Cells in a diploid plant body undergo meiosis resulting in haploid cells. Fertilization of a haploid egg cell by a haploid sperm cell results in a diploid zygote. The zygote undergoes mitosis and develops into a new diploid individual. But notice the gap between meiosis and production of gametes. This is where plant and animal life cycles differ. In plants, meiosis in structures called sporangia, result in haploid cells known as spores. The diploid plant that produces spores is the sporophyte. A haploid spore undergoes many mitotic cell divisions and develops into a haploid, multicellular individual. The sporophyte in this example is a fern, and the plant that develops from a fern's spore is shown here. The new haploid, multicellular plant is called the gametophyte because it produces gametes, egg and sperm cells. The gamete-producing structures are called gametangia. What process do you think occurs in the gametangia to produce egg and sperm cells? In the plant life cycle, unlike the human life cycle, gametes result from mitosis. This diagram summarizes the general plant life cycle. Plants are said to undergo an alternation of generations because the diploid sporophyte and haploid gametophyte are multicellular forms that occur alternately in the life cycle. Each form produces the other. All plants follow this same life cycle pattern, but each group of plants has certain variations. One variation is the relative size and longevity of the sporophyte and gametophyte. Notice that the fern sporophyte is much larger and longer-lived than the gametophyte, which is about the size of the nail on your little finger. Another variation is whether the sporophyte and gametophyte live independently of each other. This is the case in ferns.