Gymnosperms in the context of Alternation of generations


Gymnosperms in the context of Alternation of generations

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⭐ Core Definition: Gymnosperms

The gymnosperms (/ˈɪmnəˌspɜːrmz, -n-/ nə-spurmz, -⁠noh-; from Ancient Greek γυμνός (gumnós), meaning "naked", and σπέρμα (spérma), meaning "seed", and thus, "naked seed") are a group of woody, perennial seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, and Ginkgo.

The life cycle of a gymnosperm involves alternation of generations, with a dominant diploid sporophyte phase, and a reduced haploid gametophyte phase, which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to (the paraphyletic group of) all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.

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Gymnosperms in the context of Seed plants

A seed plant or spermatophyte (from Ancient Greek σπέρμα (spérma) 'seed' and φυτόν (phutón) 'plant'; lit.'seed plant'), also called a phanerogam (taxon Phanerogamae) or a phaenogam (taxon Phaenogamae), is any plant that produces seeds. It is a category of embryophyte (i.e. land plant) that includes most of the familiar land plants, including the flowering plants and the gymnosperms, but not ferns, mosses, or algae.

The term phanerogam or phanerogamae is derived from Ancient Greek φανερός (phanerós), meaning "visible", in contrast to the term "cryptogam" or "cryptogamae" (from Ancient Greek κρυπτός (kruptós) 'hidden', and γαμέω (gaméō), 'to marry'). These terms distinguish those plants with hidden sexual organs (cryptogamae) from those with visible ones (phanerogamae).

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Gymnosperms in the context of Cycad

Cycads /ˈskædz/—constituting the division Cycadophyta—are seed plants with a stout, woody cylindrical trunk with a crown of large, hard, stiff, evergreen and usually pinnate (feather-shaped) leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow slowly and have long lifespans. They superficially resemble palms or ferns, but are not closely related to either group. Cycads are gymnosperms. Cycads have specialized pollinators, usually a specific beetle, and more rarely a thrips or a moth.

Both male and female cycads bear cones (strobili) containing their seeds, somewhat resembling conifer cones. Cycads fix nitrogen in association with cyanobacteria living in the plants' roots. Some species are used as narcotics, while in Vanuatu the plant symbolizes peace and appears on the national flag. Cycads all over the world are in decline, with four species on the brink of extinction and seven species each with fewer than 100 plants left in the wild.

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Gymnosperms in the context of Ginkgo

Ginkgo is a genus of non-flowering seed plants, assigned to the gymnosperms. The scientific name is also used as the English common name. The order to which the genus belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and Ginkgo is now the only living genus within the order. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the Pliocene. The sole surviving species, Ginkgo biloba, is found in the wild only in China, but is cultivated around the world. The relationships between ginkgos and other groups of plants are not fully resolved.

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Gymnosperms in the context of Chlamydomonas

Chlamydomonas (/ˌklæmɪˈdɒmənəs, -dəˈm-/ KLAM-ih-DOM-ə-nəs, -⁠də-MOH-) is a genus of green algae consisting of about 150 species of unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogenesis, and genetics. One of the many striking features of Chlamydomonas is that it contains ion channels (channelrhodopsins) that are directly activated by light. Some regulatory systems of Chlamydomonas are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.

Molecular phylogeny studies indicated that the traditional genus Chlamydomonas as defined using morphological data, was polyphyletic within Volvocales. Many species were subsequently reclassified (e.g., Oogamochlamys, Lobochlamys), and many other "Chlamydomonas" s.l. lineages are still to be reclassified.

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Gymnosperms in the context of Robert Brown (Scottish botanist from Montrose)

Robert Brown FRSE FRS FLS MWS (21 December 1773 – 10 June 1858) was a Scottish botanist and paleobotanist who made important contributions to botany largely through his pioneering use of the microscope. His contributions include one of the earliest detailed descriptions of the cell nucleus and cytoplasmic streaming; the observation of Brownian motion; early work on plant pollination and fertilisation, including being the first to recognise the fundamental difference between gymnosperms and angiosperms; and some of the earliest studies in palynology. He also made numerous contributions to plant taxonomy, notably erecting a number of plant families that are still accepted today; and numerous Australian plant genera and species, the fruit of his exploration of that continent with Matthew Flinders.

The standard author abbreviation R.Br. is used to indicate this person as the author when citing a botanical name.

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Gymnosperms in the context of Magnoliids

Magnoliids, Magnoliidae or Magnolianae are a clade of flowering plants. With more than 10,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and many others, it is the third-largest group of angiosperms after the eudicots and monocots. The group is characterized by trimerous flowers, pollen with one pore, and usually branching-veined leaves.

Some members of the subclass are among the earliest angiosperms and share anatomical similarities with gymnosperms like stamens that resemble the male cone scales of conifers and carpels found on the long flowering axis. According to molecular clock calculations, the lineage that led to magnoliids split from other plants about 135 million years ago or 160-165 million years ago.

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Gymnosperms in the context of Tasmanian temperate rainforests

The Tasmanian temperate rain forests are a temperate broadleaf and mixed forests ecoregion in western Tasmania. The ecoregion is part of the Australasian realm, which includes Tasmania and Australia, New Zealand, New Guinea, New Caledonia, and adjacent islands.

Rainforest communities in Australia are classified as closed forests in which the canopy comprises 70–100% cover. It can be divided into tropical, subtropical, monsoon and temperate rainforest. Tasmanian rainforest is classified as cool temperate rainforest, and represents the most floristically complex and best developed form of this forest type in Australia. In Tasmania, they can be found in the West, Savage River National Park, South West, North East and in patches on the East Coast. On the mainland of Australia, cool temperate rainforest have a wide variety of woodland trees, but Tasmania only has a limited number of woodland and vascular plants such as mosses, liverworts, lichen and fungi. Because of this, the definition of Tasmanian cool temperate rainforest was redefined in the 1980s to allow for communities that did not meet the canopy requirements and clearly separate cool temperate rainforest from mixed forest; The current definition states that cool temperate rainforests are those with trees usually greater than 8 m (26 ft) in height and capable of regenerating in the absence of large scale catastrophic events, such as fire. These forests are climax vegetation and are dominated by angiosperms such as Nothofagus cunninghamii (myrtle beech), Atherosperma moschatum (sassafras), and Eucryphia lucida (leatherwood) as well as gymnosperms such as Athrotaxis selaginoides (King Billy Pine), Lagarostrobos franklinii (huon or macquarie pine) and Phyllocladus aspleniifolius (celery-top pine). The limited number of woody species is thought to be due to repeated glaciation.

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