| Gymnosperms | ||
|---|---|---|
 White Spruce leaves (needles)
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| Scientific classification | ||
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| Divisions | ||
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Pinophyta (or Coniferophyta) - Conifers |
Gymnosperm (Gymnospermae) are a group of spermatophyte seed-bearing plants with ovules on the edge or blade of an open sporophyll, which are usually arranged in cone-like structures. Picea glauca ( White Spruce) is a species of Spruce native to the north of North America, from central Alaska east to Newfoundland Plants are living Organisms belonging to the kingdom Plantae. Ginkgo is a genus of highly unusual non-flowering plants with one extant species G Cycads are a group of Seed plants characterized by a large crown of compound leaves and a stout trunk. The Plant division Gnetophyta or gnetophytes comprise three related families of Woody plants grouped in the Gymnosperms The gnetophytes differ from The spermatophytes (from the Greek word "Σπερματόφυτα" (also known as phanerogams) comprise those Plants that produce Seeds They are Plants are living Organisms belonging to the kingdom Plantae. Ovule literally means "small egg." In Seed plants the ovule is the structure that gives rise to and contains the female reproductive cells A sporophyll is a Leaf that produces Spores Sporophylls are part of the Diploid Sporophyte generation and the spores are produced by Meiosis The other major group of seed-bearing plants, the angiosperms, have ovules enclosed in a carpel, a sporophyll with fused margins. The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group A gynoecium (from Ancient Greek gyne, "woman" is the Female reproductive part of a Flower. The term gymnosperm comes from the Greek word gumnospermos, meaning "naked seeds" and referring to the unenclosed condition of the seeds, as when they are produced they are found naked on the scales of a cone or similar structure. There are between 700 and 900 species of Gymnosperm. Often they are used for many economical uses and as folk medicines. Some common uses for them are soap, varnish, lumber, paint, edible plants, and perfumes. SOAP (see below for name and origins is a protocol for exchanging XML -based messages over Computer networks normally using Varnish is a transparent, hard protective finish or film primarily used in Wood finishing but also for other materials Lumber or timber is Wood in any of its stages from felling through readiness for use as structural Material for Construction, or Paint is any Liquid, liquifiable or mastic composition which after application to a substrate in a thin layer is converted to an opaque Solid Perfume is a mixture of fragrant Essential oils and Aroma compounds Fixatives and Solvents used to give the human body animals objects and living
Gymnosperms are heterosporous, producing microspores that develop into pollen grains and megaspores that are retained in an ovule. In Biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions In Biology, a microspore is a small Spore as contrasted to the larger megaspore. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of Megaspores, also called macrospores, are a type of spores that is present in Heterosporous Plants These types of plants have two spore types megaspores After fertilization (joining of the micro- and megaspore), the resulting embryo, along with other cells comprising the ovule, develops into a seed. The seed is a sporophyte resting stage. Reproduction in gymnosperms varies greatly. Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, while conifers and gnetophytes have sperm with no flagella that are conveyed to the egg along a pollen tube which grows through ovule tissue. Cycads are a group of Seed plants characterized by a large crown of compound leaves and a stout trunk. Ginkgo is a genus of highly unusual non-flowering plants with one extant species G The Plant division Gnetophyta or gnetophytes comprise three related families of Woody plants grouped in the Gymnosperms The gnetophytes differ from A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it The pollen tube of most Seed plants acts as a conduit to transport sperm cells from the Pollen grain, either from the stigma (in Flowering plants
In early classification schemes, the gymnosperms (Gymnospermae) "naked seed" plants were regarded as a "natural" group. The Coast Douglas-fir ( Pseudotsuga menziesii var menziesii) a variety of Douglas-fir, is an Evergreen Conifer native However, certain fossil discoveries suggest that the angiosperms evolved from a gymnosperm ancestor, which would make the gymnosperms a paraphyletic group if all extinct taxa are included. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Modern cladistics only accepts taxa that are monophyletic, traceable to a common ancestor and inclusive of all descendants of that common ancestor. Cladistics is the hierarchical classification of Species based on evolutionary ancestry A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor So, while the term 'gymnosperm' is still widely used for non-angiosperm seed-bearing plants, the plant species once treated as gymnosperms are usually distributed among four groups, which can be given equal rank as divisions within the Kingdom Plantae.
Molecular phylogenies of extant gymnosperms have conflicted with morphological datasets with regard to whether they comprise a monophyletic group or a paraphyletic one that gave rise to angiosperms. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all At issue is whether the Gnetophyta are the sister group of angiosperms, or whether they are sister to, or nested within, other extant gymnosperms. The Plant division Gnetophyta or gnetophytes comprise three related families of Woody plants grouped in the Gymnosperms The gnetophytes differ from Cladistics is the hierarchical classification of Species based on evolutionary ancestry Numerous fossil gymnosperm clades once existed that are morphologically at least as distinctive as the four living gymnosperm groups, such as Bennettitales, Caytonia and the glossopterids. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Bennettitales (the cycadeoids) is an extinct order of seed plants that first appeared in the Triassic period and became extinct toward When these groups are considered the question of gymnosperm and angiosperm relationships becomes even more complicated.
References
- Burleigh, J. G. , and S. Mathews. 2004. Phylogenetic signal in nucleotide data from seed plants: implications for resolving the seed plant tree of life. American Journal of Botany 91: 1599-1613 (abstract)
- Gifford, Ernest M. , Adriance S. Foster. 1989. Morphology and Evolution of Vascular Plants. Third edition. WH Freeman and Company, New York.
- Hilton, Jason, and Richard M. Bateman. 2006. Pteridosperms are the backbone of seed-plant phylogeny. Journal of the Torrey Botanical Society 133: 119-168 (abstract)
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