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The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes
conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All exta ...

conifers
,
cycad :''For the insect, see Cicada.'' Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious ...

cycad
s, ''
Ginkgo ''Ginkgo'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their ...

Ginkgo
'', and
gnetophyte Gnetophyta () is a division of plants, grouped within the gymnosperm The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes. The term "gymnosperm ...
s, forming the clade Gymnospermae, the living members of which are also known as Acrogymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνόσπερμος ( el, γυμνός, translit=gymnos, lit=naked, label=none and el, σπέρμα, translit=sperma, lit=seed, label=none), literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds (called
ovule In seed plant The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or l ...

ovule
s in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (
angiosperms Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...
), which are enclosed within an
ovary The ovary is an organ found in the female reproductive system 400px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" ;"title="Labia_minora.html" ...
. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form
cones A cone is a three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameter A parameter (from the Ancient Greek language, Ancient Greek wikt:πα ...
, or solitary as in
yew
yew
, ''
Torreya ''Torreya'' is a genus of Pinophyta, conifers comprising six or seven species placed the family Taxaceae, though sometimes formerly placed in Cephalotaxaceae. Four species are native to eastern Asia; the other two are native to North America. T ...
'', ''
Ginkgo ''Ginkgo'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their ...

Ginkgo
''. Gymnosperms show alternation of generations; and have a dominant diploid sporophytic phase, a reduced haploid gametophytic phase which is dependent on the sporophytic phase. The gymnosperms and
angiosperms Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...
together compose the
spermatophyte The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the pl ...
s or seed plants. The gymnosperms are divided into six phyla. Organisms that belong to the Cycadophyta, Ginkgophyta, Gnetophyta, and Pinophyta (also known as Coniferophyta) phyla are still in existence while those in the Pteridospermales and Cordaitales phyla are now extinct. By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes (''
Gnetum ''Gnetum'' is a genus of gymnosperm The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes. The term "gymnosperm" comes from the composite word in ...
'', ''
Ephedra , an alkaloid found in ephedra Ephedra is a medicinal preparation from the plant '' Ephedra sinica''. Several additional species belonging to the genus ''Ephedra (genus), Ephedra'' have traditionally been used for a variety of medicinal purposes, ...
'' and ''
Welwitschia ''Welwitschia'' is a monotypic taxon, monotypic gymnosperm genus, comprising solely the distinctive ''Welwitschia mirabilis'', Endemism, endemic to the Namib desert within Namibia and Angola. The plant is commonly known simply as welwitschia in En ...

Welwitschia
''), and ''
Ginkgo biloba ''Ginkgo biloba'', commonly known as ginkgo or gingko ( ) also known as the maidenhair tree, is a species of tree native to China. It is the last living species in the order Ginkgoales, which first appeared over 290 million years ago. Fossils v ...

Ginkgo biloba
'' (a single living species). About 65% of gymnosperms are
dioecious Dioecy (; Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as o ...
, but conifers are almost all
monoecious Monoecy (; adjective form: monoecious ) is a sexual system in seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plants are predominantly photosynthet ...

monoecious
. Some genera have
mycorrhiza A mycorrhiza (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mi ...

mycorrhiza
, fungal associations with roots (''Pinus''), while in some others (''Cycas'') small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria.


Classification

A formal classification of the living gymnosperms is the "Acrogymnospermae", which form a
monophyletic group A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual cont ...
within the
spermatophyte The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the pl ...
s. The wider "Gymnospermae" group includes extinct gymnosperms and is thought to be
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...
. The fossil record of gymnosperms includes many distinctive
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
that do not belong to the four modern groups, including seed-bearing trees that have a somewhat
fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses and other bryophytes by being vascular, ...

fern
-like vegetative morphology (the so-called "seed ferns" or
pteridosperm The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") refers to several distinct polyphyletic File:Monophyly, paraphyly, polyphyly.png, 300px, Cladogram of the primates, showing a monophyly (the simians, in yellow), a paraphyl ...
s). When fossil gymnosperms such as these and the Bennettitales, glossopterids, and ''Caytonia'' are considered, it is clear that angiosperms are nested within a larger gymnospermae clade, although which group of gymnosperms is their closest relative remains unclear. The extant gymnosperms include 12 main families and 83 genera which contain more than 1000 known species. Subclass Cycadidae *Order Cycadales **Family Cycadaceae: ''Cycas'' **Family Zamiaceae: ''Dioon'', ''Bowenia'', ''Macrozamia'', ''Lepidozamia'', ''Encephalartos'', ''Stangeria'', ''Ceratozamia'', ''Microcycas'', ''Zamia'' Subclass Ginkgoidae *Order Ginkgoales **Family Ginkgoaceae: ''
Ginkgo ''Ginkgo'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their ...

Ginkgo
'' Subclass Gnetidae *Order Welwitschiales **Family Welwitschiaceae: ''
Welwitschia ''Welwitschia'' is a monotypic taxon, monotypic gymnosperm genus, comprising solely the distinctive ''Welwitschia mirabilis'', Endemism, endemic to the Namib desert within Namibia and Angola. The plant is commonly known simply as welwitschia in En ...

Welwitschia
'' *Order Gnetales **Family Gnetaceae: ''
Gnetum ''Gnetum'' is a genus of gymnosperm The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes. The term "gymnosperm" comes from the composite word in ...
'' *Order Ephedrales **Family Ephedraceae: ''Ephedra (plant), Ephedra'' Subclass Pinidae *Order Pinales **Family Pinaceae: ''Cedrus'', ''Pinus'', ''Cathaya'', ''Picea'', ''Pseudotsuga'', ''Larix'', ''Pseudolarix'', ''Tsuga'', ''Nothotsuga'', ''Keteleeria'', ''Abies'' *Order Araucariales **Family Araucariaceae: ''Araucaria'', ''Wollemia'', ''Agathis'' **Family Podocarpaceae: ''Phyllocladus'', ''Lepidothamnus'', ''Prumnopitys'', ''Sundacarpus'', ''Halocarpus'', ''Parasitaxus'', ''Lagarostrobos'', ''Manoao'', ''Saxegothaea'', ''Microcachrys'', ''Pherosphaera'', ''Acmopyle'', ''Dacrycarpus'', ''Dacrydium'', ''Falcatifolium'', ''Retrophyllum'', ''Nageia'', ''Afrocarpus'', ''Podocarpus'' *Order Cupressales **Family Sciadopityaceae: ''Sciadopitys'' **Family Cupressaceae: ''Cunninghamia'', ''Taiwania'', ''Athrotaxis'', ''Metasequoia'', ''Sequoioideae, Sequoia'', ''Sequoiadendron'', ''Cryptomeria'', ''Glyptostrobus'', ''Taxodium'', ''Papuacedrus'', ''Austrocedrus'', ''Libocedrus'', ''Pilgerodendron'', ''Widdringtonia'', ''Diselma'', ''Fitzroya'', ''Callitris'', ''Actinostrobus'', ''Neocallitropsis'', ''Thujopsis'', ''Thuja'', ''Fokienia'', ''Chamaecyparis'', ''Cupressus'', ''Juniperus'', ''Calocedrus'', ''Tetraclinis'', ''Platycladus'', ''Microbiota (plant), Microbiota'' **Family Taxaceae: ''Austrotaxus'', ''Pseudotaxus'', ''Taxus'', ''Cephalotaxus'', ''Amentotaxus'', ''
Torreya ''Torreya'' is a genus of Pinophyta, conifers comprising six or seven species placed the family Taxaceae, though sometimes formerly placed in Cephalotaxaceae. Four species are native to eastern Asia; the other two are native to North America. T ...
''


Extinct groupings

* Order Bennettitales ** Family Cycadeoidaceae ** Family Williamsoniaceae * Order Erdtmanithecales *Order Pentoxylales *Order Czekanowskiales


Diversity and origin

Over 1000 living species of gymnosperm exist. It is widely accepted that the gymnosperms originated in the late Carboniferous period, replacing the Lycopodiophyta, lycopsid rainforests of the tropical region. This development appears to have resulted from a whole Gene duplication, genome duplication event around .Jiao Y, Wickett NJ, Ayyampalayam S, Chanderbali AS, Landherr L, Ralph PE, Tomsho LP, Hu Y, Liang H, Soltis PS, Douglas E. Soltis, Soltis DE, Clifton SW, Schlarbaum SE, Schuster SC, Ma H, Leebens-Mack J, Depamphilis CW (2011) Ancestral polyploidy in seed plants and angiosperms. Nature Early characteristics of seed plants are evident in fossil progymnosperms of the late Devonian period around 383 million years ago. It has been suggested that during the mid-Mesozoic era, pollination of some extinct groups of gymnosperms was by extinct species of Mecoptera, scorpionflies that had specialized proboscis for feeding on pollination drops. The scorpionflies likely engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms. Evidence has also been found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatidae, Kalligrammatid lacewings, a now-extinct family with members which (in an example of convergent evolution) resembled the modern butterflies that arose far later. Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65–70 genera and 600–630 species (696 accepted names).Catalogue of Life: 2007 Annual checklist – Conifer database
Conifers are woody plants and most are evergreens. The leaf, leaves of many conifers are long, thin and needle-like, other species, including most Cupressaceae and some Podocarpaceae, have flat, triangular scale-like leaves. ''Agathis'' in Araucariaceae and ''Nageia'' in Podocarpaceae have broad, flat strap-shaped leaves. 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 Gnetum, Gnetales and one species of
Ginkgo ''Ginkgo'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their ...

Ginkgo
.


Uses

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.


Life cycle

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. Like all seed plants, they are heterospory, heterosporous, having two spore types, microspores (male) and megaspores (female) that are typically produced in pollen cones or ovulate cones, respectively. As with all heterosporous plants, the gametophytes 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 Archegonium, 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 ''Ginkgo'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their ...

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 Fertilisation, 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#Seed plants, gametophyte, which serves as a food supply, and the seed coat.


Genetics

The first published sequenced genome for any gymnosperm was the genome of ''Picea abies'' in 2013.


References


Bibliography

*


External links


Gymnosperm DatabaseGymnosperms on the Tree of Life
* {{Authority control Gymnosperms, 01 Extant Late Devonian first appearances