Raffi: outline of breakout

2009-05-04T21:45:03Z

outline of breakout

Raffi at 04:52, 4 April 2007

2007-04-04T04:52:53Z

New page

The '''spermatophytes''' (also known as '''phanerogams''') comprise those [[plant]]s that produce [[seed]]s. They are a subset of the [[embryophyte]]s or land plants. The living spermatophytes form five groups:

*[[cycad]]s, a subtropical and tropical group of plants with a large crown of compound leaves and a stout trunk,
*''[[Ginkgo]]'', a single species of [[tree]],
*[[conifers]], cone-bearing trees and [[shrub]]s,
*[[gnetae]], [[woody plant]]s in the genera ''[[Gnetum]]'', ''[[Welwitschia]]'', and ''[[Ephedra (genus)|Ephedra]]'', and
*[[angiosperms]], the flowering plants, a large group including many familiar plants in a wide variety of habitats.

===Relationships and nomenclature===
Seed-bearing plants were traditionally divided into [[angiosperm]]s, or flowering plants, and [[gymnosperm]]s, which includes the gnetae, cycads, ginkgo, and conifers. Angiosperms are now thought to have evolved from a gymnosperm ancestor, which would make gymnosperms a [[paraphyletic]] group if it includes extinct taxa. Although not a [[monophyletic]] taxonomic unit, "gymnosperm" is still widely used to distinguish the four taxa of non-flowering, seed-bearing plants from the angiosperms.

[[Molecular phylogeny|Molecular phylogenies]] have conflicted with [[Morphology (biology)|morphologically]]-based evidence as to whether extant gymnosperms comprise a monophyletic group. Some morphological data suggests that the Gnetophytes are the sister-group to angiosperms, but molecular phylogenies have generally shown a gymnosperm clade that includes the Gnetophytes as sister-group to the conifers.

A traditional classification grouped put all the seed plants in a single [[division (biology)|division]], with [[class (taxonomy)|class]]es for our five groups:
*Division '''Spermatophyta'''
**'''[[Cycad|Cycadopsida]]''', the cycads
**'''[[Ginkgo|Ginkgoopsida]]''', the ginkgo
**'''[[Pinopsida]]''', the conifers, ("Coniferopsida")
**'''[[Gnetae|Gnetopsida]]''', the gnetae
**'''[[Magnoliopsida]]''', the [[flowering plant]]s, or '''Angiospermopsida'''

In addition to the taxa listed above, the fossil record contains evidence of many [[extinct]] taxa of seed plants. The so-called "seed ferns" ([[Pteridospermae]]) were one of the earliest successful groups of land plants, and forests dominated by seed ferns were prevalent in the late [[Paleozoic]]. ''[[Glossopteris]]'' was the most prominent [[tree]] [[genus]] in the ancient southern [[supercontinent]] of [[Gondwana]] during the [[Permian]] period. By the [[Triassic]] period, seed ferns had declined in ecological importance, and representatives of modern gymnosperm groups were abundant and dominant through the end of the [[Cretaceous]], when angiosperms radiated.

A more modern classification ranks these groups as separate divisions (sometimes under the '''Superdivision Spermatophyta'''):
*'''[[Cycad|Cycadophyta]]''', the cycads
*'''[[Ginkgo|Ginkgophyta]]''', the ginkgo
*'''[[Pinophyta]]''', the [[conifer]]s
*'''[[Gnetae|Gnetophyta]]''', the gnetae
*'''[[Flowering plant|Magnoliophyta]]''', the [[flowering plant]]s

== References ==
*Bowe, L. Michelle, Gwénaële Coat, and Claude W. dePamphilis. 2000. Phylogeny of seed plants based on all three genomic compartments: Extant gymnosperms are monophyletic and Gnetales' closest relatives are conifers. ''Proceedings of the National Academy of Sciences'' 97: 4092-4097.
*Soltis, Douglas E., Pamela S. Soltis and Michael J. Zanis. 2002. Phylogeny of seed plants based on evidence from eight genes. ''American Journal of Botany'' 89: 1670-1681 (abstract [http://intl.amjbot.org/cgi/content/full/89/10/1670 here]).
*Chaw, Shu-Miaw, Christopher L. Parkinson, Yuchang Cheng, Thomas M. Vincent, and Jeffrey D. Palmer. 2000. Seed plant phylogeny inferred from all three plant genomes: Monophyly of extant gymnosperms and origin of Gnetales from conifers. ''Proceedings of the National Academy of Sciences'' 97: 4086-4091 (abstract [http://www.pnas.org/cgi/content/abstract/97/8/4086 here]).

[[Category:Plants| sort30 Spermatophyta]]

Spermatophyte - Revision history

Raffi: outline of breakout

Raffi at 04:52, 4 April 2007