<P> Cycads are the next most abundant group of gymnosperms, with two or three families, 11 genera, and approximately 338 species . A majority of cycads are native to tropical climates and are most abundantly found in regions near the equator . The other extant groups are the 95 - 100 species of Gnetales and one species of Ginkgo . </P> <P> Gymnosperms have major economic uses . Pine, fir, spruce, and cedar are all examples of conifers that are used for lumber, paper production, and resin . Some other common uses for gymnosperms are soap, varnish, nail polish, food, gum, and perfumes . </P> <P> Gymnosperms, like all vascular plants, have a sporophyte - dominant life cycle, which means they spend most of their life cycle with diploid cells, while the gametophyte (gamete - bearing phase) is relatively short - lived . Two spore types, microspores and megaspores, are typically produced in pollen cones or ovulate cones, respectively . Gametophytes, as with all heterosporous plants, develop within the spore wall . Pollen grains (microgametophytes) mature from microspores, and ultimately produce sperm cells . Megagametophytes develop from megaspores and are retained within the ovule . Gymnosperms produce multiple archegonia, which produce the female gamete . During pollination, pollen grains are physically transferred between plants from the pollen cone to the ovule . Pollen is usually moved by wind or insects . Whole grains enter each ovule through a microscopic gap in the ovule coat (integument) called the micropyle . The pollen grains mature further inside the ovule and produce sperm cells . Two main modes of fertilization are found in gymnosperms . Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, whereas conifers and gnetophytes have sperm with no flagella that are moved along a pollen tube to the egg . After syngamy (joining of the sperm and egg cell), the zygote develops into an embryo (young sporophyte). More than one embryo is usually initiated in each gymnosperm seed . The mature seed comprises the embryo and the remains of the female gametophyte, which serves as a food supply, and the seed coat . </P> <P> The first published sequenced genome for any gymnosperm was the genome of Picea abies in 2013 . </P>

When did the gymnosperm evolve write briefly about the main trends of evolution