Plant (organism): Difference between revisions
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The '''green plants''' (from the Latin ''planta'', meaning "sprout") are those [[organism]]s classified into the [[kingdom (biology)|kingdom]] '''Plantae'''. Descending from a single [[common ancestor]], the plants take up a large portion of [[life]]—with estimates exceeding 285,000 [[species]]—and include many familiar and ubiquitous species including [[tree]]s, [[shrub]]s, [[cactus|cacti]], [[grass]]es, [[herb]]s, [[fern]]s, [[moss]]es, and [[green algae]]. Plants share certain characteristics—unlike [[animal]]s and [[fungi]], they do not voluntarily move, typically growing in a permanent site, passively absorbing [[nutrients]] and [[energy]] from their environment. In terms of both their total mass and their importance to other organisms, the green plants dominate [[ecosystem]]s in both [[land]] and [[freshwater]]. By harnessing [[sunlight]], they act as the primary | The '''green plants''' (from the Latin ''planta'', meaning "sprout") are those [[organism]]s classified into the [[kingdom (biology)|kingdom]] '''Plantae'''. Descending from a single [[common ancestor]], the plants take up a large portion of [[life]]—with estimates exceeding 285,000 [[species]]—and include many familiar and ubiquitous species including [[tree]]s, [[shrub]]s, [[cactus|cacti]], [[grass]]es, [[herb]]s, [[fern]]s, [[moss]]es, and [[green algae]]. Plants share certain characteristics—unlike [[animal]]s and [[fungi]], they do not voluntarily move, typically growing in a permanent site, passively absorbing [[nutrients]] and [[energy]] from their environment. In terms of both their total mass and their importance to other organisms, the green plants dominate [[ecosystem]]s in both [[land]] and [[freshwater]]. By harnessing [[sunlight]] through [[photosynthesis]], they act as the primary [[producers]] of [[food]] for all life in those ecosystems: green algae in freshwater and [[land plant]]s on the land. | ||
== | ==Definitions== | ||
The term "plant" has gone through several definitions along history. Plants, which do not move, were distinguished from animals, which do move, by [[Aristotle]] in his works on [[metaphysics]] and [[logic]]. Aristotle continued to influence classification of plants all the way to [[Carl Linnaeus]], who divided all life into the two kingdoms ''Vegetabilia'' (or ''Plantae'') and ''[[Animalia]]''. [[Fungi]] and [[protist]]s were originally grouped into Plantae, but they were moved into their own kingdoms when it became clear that they were very different from plants. | The term "plant" has gone through several definitions along history. Plants, which do not move, were distinguished from animals, which do move, by [[Aristotle]] in his works on [[metaphysics]] and [[logic]]. Aristotle continued to influence classification of plants all the way to [[Carl Linnaeus]], who divided all life into the two kingdoms ''Vegetabilia'' (or ''Plantae'') and ''[[Animalia]]''. [[Fungi]] and [[protist]]s were originally grouped into Plantae, but they were moved into their own kingdoms when it became clear that they were very different from plants. | ||
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Most of the algae are still considered separate from the land plants today. The [[green algae]], however, have recently been placed back into the Plantae, as they form a [[clade]] with the land plants (meaning the green algae and land plants are descended from one common ancestor). | Most of the algae are still considered separate from the land plants today. The [[green algae]], however, have recently been placed back into the Plantae, as they form a [[clade]] with the land plants (meaning the green algae and land plants are descended from one common ancestor). | ||
==Characteristics== | |||
From the first green algae growing on ancient, muddy shores, the plants were the first organisms that could stay alive completely exposed to the air. As they colonized the land, they diversified into an astonishing array of light-capturing, reproducing machines. Living on land would dry out and kill vulnerable cells, and yet it also offers a windfall of resources and unfiltered sunlight, both which are scare in aquatic environments. Therefore, despite their diversity some themes thus appear within the plants, as a result of having to cope with the unique, common problems of living and reproducing on land. | |||
===Cells=== | |||
Like the other photosynthetic organisms, plant cells contain chlorophyll. | |||
==Origin and phylogeny== | ==Origin and phylogeny== | ||
Revision as of 16:32, 3 May 2009
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 Cypripedium reginae
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The green plants (from the Latin planta, meaning "sprout") are those organisms classified into the kingdom Plantae. Descending from a single common ancestor, the plants take up a large portion of life—with estimates exceeding 285,000 species—and include many familiar and ubiquitous species including trees, shrubs, cacti, grasses, herbs, ferns, mosses, and green algae. Plants share certain characteristics—unlike animals and fungi, they do not voluntarily move, typically growing in a permanent site, passively absorbing nutrients and energy from their environment. In terms of both their total mass and their importance to other organisms, the green plants dominate ecosystems in both land and freshwater. By harnessing sunlight through photosynthesis, they act as the primary producers of food for all life in those ecosystems: green algae in freshwater and land plants on the land.
Definitions
The term "plant" has gone through several definitions along history. Plants, which do not move, were distinguished from animals, which do move, by Aristotle in his works on metaphysics and logic. Aristotle continued to influence classification of plants all the way to Carl Linnaeus, who divided all life into the two kingdoms Vegetabilia (or Plantae) and Animalia. Fungi and protists were originally grouped into Plantae, but they were moved into their own kingdoms when it became clear that they were very different from plants.
At this time, the algae were reclassified as protists, which included a hodgepodge of many unrelated aquatic organisms that, like land plants, could capture energy from sunlight using photosynthesis but had developed it independently. The many varieties of seaweed, for instance, may resemble land plants but are divided among the green, red, and brown algae.
Most of the algae are still considered separate from the land plants today. The green algae, however, have recently been placed back into the Plantae, as they form a clade with the land plants (meaning the green algae and land plants are descended from one common ancestor).
Characteristics
From the first green algae growing on ancient, muddy shores, the plants were the first organisms that could stay alive completely exposed to the air. As they colonized the land, they diversified into an astonishing array of light-capturing, reproducing machines. Living on land would dry out and kill vulnerable cells, and yet it also offers a windfall of resources and unfiltered sunlight, both which are scare in aquatic environments. Therefore, despite their diversity some themes thus appear within the plants, as a result of having to cope with the unique, common problems of living and reproducing on land.
Cells
Like the other photosynthetic organisms, plant cells contain chlorophyll.
Origin and phylogeny
Despite Phylogeny changing many of the concepts of how plants should be classified and what divisions remain, currently plants are informally divided among four main groups called; green algae, about 8.000 species; non vascular plants, or Bryophytes, circa 20.000 species; the ferns and horsetails, or Pteridophytes, around 12,000; and seed plants, that is the largest group with 260,000 estimated species. These are split in twelve total divisions:
- Chlorophyta: part of green algae
- Charophyta: the rest of green algae
- Marchantiophyta: liverworts
- Anthocerotophyta: hornworts
- Bryophyta: mosses
- Lycopodiophyta: club mosses
- Pteridophyta: ferns
- Cycadophyta: cycads
- Ginkgophyta: ginkgo
- Pinophyta: conifers
- Gnetophyta: gnetophytes
- Magnoliophyta: flowering plants