51-648: See text Plants are the eukaryotes that form the kingdom Plantae ; they are predominantly photosynthetic . This means that they obtain their energy from sunlight , using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars from carbon dioxide and water, using the green pigment chlorophyll . Exceptions are parasitic plants that have lost the genes for chlorophyll and photosynthesis, and obtain their energy from other plants or fungi. Most plants are multicellular , except for some green algae. Historically, as in Aristotle's biology ,
102-405: A microtubular spindle during nuclear division, in the distinctively eukaryotic process of mitosis . Eukaryotes differ from prokaryotes in multiple ways, with unique biochemical pathways such as sterane synthesis. The eukaryotic signature proteins have no homology to proteins in other domains of life, but appear to be universal among eukaryotes. They include the proteins of the cytoskeleton,
153-518: A "symbiosis-based phylogeny", giving the description "Eukarya (symbiosis-derived nucleated organisms)". By 2014, a rough consensus started to emerge from the phylogenomic studies of the previous two decades. The majority of eukaryotes can be placed in one of two large clades dubbed Amorphea (similar in composition to the unikont hypothesis) and the Diphoda (formerly bikonts), which includes plants and most algal lineages. A third major grouping,
204-430: A body, with its cells dividing by mitosis , and at some stage produce haploid gametes through meiosis , a division that reduces the number of chromosomes and creates genetic variability . There is considerable variation in this pattern. Plants have both haploid and diploid multicellular phases . Eukaryotes have lower metabolic rates and longer generation times than prokaryotes, because they are larger and therefore have
255-479: A bundle of microtubules arising from a centriole , characteristically arranged as nine doublets surrounding two singlets. Flagella may have hairs ( mastigonemes ), as in many stramenopiles . Their interior is continuous with the cell's cytoplasm . Centrioles are often present, even in cells and groups that do not have flagella, but conifers and flowering plants have neither. They generally occur in groups that give rise to various microtubular roots. These form
306-406: A primary component of the cytoskeleton, and are often assembled over the course of several cell divisions, with one flagellum retained from the parent and the other derived from it. Centrioles produce the spindle during nuclear division. The cells of plants, algae, fungi and most chromalveolates , but not animals, are surrounded by a cell wall. This is a layer outside the cell membrane , providing
357-546: A protective response. The first such plant receptors were identified in rice and in Arabidopsis thaliana . Plants have some of the largest genomes of all organisms. The largest plant genome (in terms of gene number) is that of wheat ( Triticum aestivum ), predicted to encode ≈94,000 genes and thus almost 5 times as many as the human genome . The first plant genome sequenced was that of Arabidopsis thaliana which encodes about 25,500 genes. In terms of sheer DNA sequence,
408-418: A range of physical and biotic stresses which cause DNA damage , but they can tolerate and repair much of this damage. Plants reproduce to generate offspring, whether sexually , involving gametes , or asexually , involving ordinary growth. Many plants use both mechanisms. When reproducing sexually, plants have complex lifecycles involving alternation of generations . One generation, the sporophyte , which
459-510: A smaller surface area to volume ratio. The evolution of sexual reproduction may be a primordial characteristic of eukaryotes. Based on a phylogenetic analysis, Dacks and Roger have proposed that facultative sex was present in the group's common ancestor. A core set of genes that function in meiosis is present in both Trichomonas vaginalis and Giardia intestinalis , two organisms previously thought to be asexual. Since these two species are descendants of lineages that diverged early from
510-417: A system of domains rather than kingdoms as top level rank being put forward by Carl Woese , Otto Kandler , and Mark Wheelis in 1990, uniting all the eukaryote kingdoms in the domain "Eucarya", stating, however, that " 'eukaryotes' will continue to be an acceptable common synonym". In 1996, the evolutionary biologist Lynn Margulis proposed to replace kingdoms and domains with "inclusive" names to create
561-403: Is diploid (with 2 sets of chromosomes ), gives rise to the next generation, the gametophyte , which is haploid (with one set of chromosomes). Some plants also reproduce asexually via spores . In some non-flowering plants such as mosses, the sexual gametophyte forms most of the visible plant. In seed plants (gymnosperms and flowering plants), the sporophyte forms most of the visible plant, and
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#1732772680556612-544: Is a similar process. Structures such as runners enable plants to grow to cover an area, forming a clone . Many plants grow food storage structures such as tubers or bulbs which may each develop into a new plant. Some non-flowering plants, such as many liverworts, mosses and some clubmosses, along with a few flowering plants, grow small clumps of cells called gemmae which can detach and grow. Plants use pattern-recognition receptors to recognize pathogens such as bacteria that cause plant diseases. This recognition triggers
663-610: Is closer in structure to bacterial RNA than to eukaryote RNA. Some eukaryotes, such as the metamonads Giardia and Trichomonas , and the amoebozoan Pelomyxa , appear to lack mitochondria, but all contain mitochondrion-derived organelles, like hydrogenosomes or mitosomes , having lost their mitochondria secondarily. They obtain energy by enzymatic action in the cytoplasm. Plants and various groups of algae have plastids as well as mitochondria. Plastids, like mitochondria, have their own DNA and are developed from endosymbionts , in this case cyanobacteria . They usually take
714-493: Is known as botany , a branch of biology . All living things were traditionally placed into one of two groups, plants and animals . This classification dates from Aristotle (384–322 BC), who distinguished different levels of beings in his biology , based on whether living things had a "sensitive soul" or like plants only a "vegetative soul". Theophrastus , Aristotle's student, continued his work in plant taxonomy and classification. Much later, Linnaeus (1707–1778) created
765-643: Is much larger than that of prokaryotes. The eukaryotes seemingly emerged within the Asgard archaea , and are closely related to the Heimdallarchaeia . This implies that there are only two domains of life , Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes first emerged during the Paleoproterozoic , likely as flagellated cells. The leading evolutionary theory
816-536: Is that their cells have nuclei . This gives them their name, from the Greek εὖ ( eu , "well" or "good") and κάρυον ( karyon , "nut" or "kernel", here meaning "nucleus"). Eukaryotic cells have a variety of internal membrane-bound structures, called organelles , and a cytoskeleton which defines the cell's organization and shape. The nucleus stores the cell's DNA , which is divided into linear bundles called chromosomes ; these are separated into two matching sets by
867-868: Is they were created by symbiogenesis between an anaerobic Asgard archaean and an aerobic proteobacterium , which formed the mitochondria . A second episode of symbiogenesis with a cyanobacterium created the plants, with chloroplasts . Eukaryotic cells contain membrane-bound organelles such as the nucleus , the endoplasmic reticulum , and the Golgi apparatus . Eukaryotes may be either unicellular or multicellular . In comparison, prokaryotes are typically unicellular. Unicellular eukaryotes are sometimes called protists . Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion ( fertilization ). Eukaryotes are organisms that range from microscopic single cells , such as picozoans under 3 micrometres across, to animals like
918-709: The Antarctic flora , consisting of algae, mosses, liverworts, lichens, and just two flowering plants, have adapted to the prevailing conditions on that southern continent. Plants are often the dominant physical and structural component of the habitats where they occur. Many of the Earth's biomes are named for the type of vegetation because plants are the dominant organisms in those biomes, such as grassland , savanna , and tropical rainforest . Eukaryote The eukaryotes ( / j uː ˈ k ær i oʊ t s , - ə t s / yoo- KARR -ee-ohts, -əts ) constitute
969-700: The Cretaceous so rapid that Darwin called it an " abominable mystery ". Conifers diversified from the Late Triassic onwards, and became a dominant part of floras in the Jurassic . In 2019, a phylogeny based on genomes and transcriptomes from 1,153 plant species was proposed. The placing of algal groups is supported by phylogenies based on genomes from the Mesostigmatophyceae and Chlorokybophyceae that have since been sequenced. Both
1020-1222: The Excavata , has been abandoned as a formal group as it is paraphyletic . The proposed phylogeny below includes only one group of excavates ( Discoba ), and incorporates the 2021 proposal that picozoans are close relatives of rhodophytes. The Provora are a group of microbial predators discovered in 2022. Ancyromonadida [REDACTED] Malawimonada [REDACTED] CRuMs [REDACTED] Amoebozoa [REDACTED] Breviatea [REDACTED] Apusomonadida [REDACTED] Holomycota (inc. fungi) [REDACTED] Holozoa (inc. animals) [REDACTED] ? Metamonada [REDACTED] Discoba [REDACTED] Cryptista [REDACTED] Rhodophyta (red algae) [REDACTED] Picozoa [REDACTED] Glaucophyta [REDACTED] Viridiplantae (plants) [REDACTED] Hemimastigophora [REDACTED] Provora [REDACTED] Haptista [REDACTED] Telonemia [REDACTED] Rhizaria [REDACTED] Alveolata [REDACTED] Stramenopiles [REDACTED] [REDACTED] World Flora Online Too Many Requests If you report this error to
1071-518: The archaea —having a volume of around 10,000 times greater. Eukaryotes represent a small minority of the number of organisms , but, as many of them are much larger, their collective global biomass (468 gigatons) is far larger than that of prokaryotes (77 gigatons), with plants alone accounting for over 81% of the total biomass of Earth . The eukaryotes are a diverse lineage, consisting mainly of microscopic organisms . Multicellularity in some form has evolved independently at least 25 times within
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#17327726805561122-583: The blue whale , weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long, or plants like the coast redwood , up to 120 metres (390 ft) tall. Many eukaryotes are unicellular; the informal grouping called protists includes many of these, with some multicellular forms like the giant kelp up to 200 feet (61 m) long. The multicellular eukaryotes include the animals, plants, and fungi , but again, these groups too contain many unicellular species . Eukaryotic cells are typically much larger than those of prokaryotes —the bacteria and
1173-456: The carpels or ovaries , which develop into fruits that contain seeds . Fruits may be dispersed whole, or they may split open and the seeds dispersed individually. Plants reproduce asexually by growing any of a wide variety of structures capable of growing into new plants. At the simplest, plants such as mosses or liverworts may be broken into pieces, each of which may regrow into whole plants. The propagation of flowering plants by cuttings
1224-558: The domain of Eukaryota or Eukarya , organisms whose cells have a membrane-bound nucleus . All animals , plants , fungi , and many unicellular organisms are eukaryotes. They constitute a major group of life forms alongside the two groups of prokaryotes : the Bacteria and the Archaea . Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass
1275-514: The taxonomic rank of kingdom by Linnaeus in the 18th century. Though he included the fungi with plants with some reservations, it was later realized that they are quite distinct and warrant a separate kingdom. The various single-cell eukaryotes were originally placed with plants or animals when they became known. In 1818, the German biologist Georg A. Goldfuss coined the word Protozoa to refer to organisms such as ciliates , and this group
1326-998: The "chlorophyte algae" and the "streptophyte algae" are treated as paraphyletic (vertical bars beside phylogenetic tree diagram) in this analysis, as the land plants arose from within those groups. The classification of Bryophyta is supported both by Puttick et al. 2018, and by phylogenies involving the hornwort genomes that have also since been sequenced. Rhodophyta [REDACTED] Glaucophyta [REDACTED] Chlorophyta [REDACTED] Prasinococcales Mesostigmatophyceae Chlorokybophyceae Spirotaenia [REDACTED] Klebsormidiales [REDACTED] Chara [REDACTED] Coleochaetales [REDACTED] Hornworts [REDACTED] Liverworts [REDACTED] Mosses [REDACTED] Lycophytes [REDACTED] [REDACTED] Gymnosperms [REDACTED] Angiosperms [REDACTED] Plant cells have distinctive features that other eukaryotic cells (such as those of animals) lack. These include
1377-864: The Viridiplantae, along with the red algae and the glaucophytes , in the clade Archaeplastida . There are about 380,000 known species of plants, of which the majority, some 260,000, produce seeds . They range in size from single cells to the tallest trees . Green plants provide a substantial proportion of the world's molecular oxygen; the sugars they create supply the energy for most of Earth's ecosystems and other organisms , including animals, either eat plants directly or rely on organisms which do so. Grain , fruit , and vegetables are basic human foods and have been domesticated for millennia. People use plants for many purposes , such as building materials , ornaments, writing materials , and, in great variety, for medicines . The scientific study of plants
1428-798: The amount of cytoplasm stays the same. Most plants are multicellular . Plant cells differentiate into multiple cell types, forming tissues such as the vascular tissue with specialized xylem and phloem of leaf veins and stems , and organs with different physiological functions such as roots to absorb water and minerals, stems for support and to transport water and synthesized molecules, leaves for photosynthesis, and flowers for reproduction. Plants photosynthesize , manufacturing food molecules ( sugars ) using energy obtained from light . Plant cells contain chlorophylls inside their chloroplasts, which are green pigments that are used to capture light energy. The end-to-end chemical equation for photosynthesis is: This causes plants to release oxygen into
1479-426: The atmosphere. Green plants provide a substantial proportion of the world's molecular oxygen, alongside the contributions from photosynthetic algae and cyanobacteria. Plants that have secondarily adopted a parasitic lifestyle may lose the genes involved in photosynthesis and the production of chlorophyll. Growth is determined by the interaction of a plant's genome with its physical and biotic environment. Factors of
1530-465: The basis of the modern system of scientific classification , but retained the animal and plant kingdoms , naming the plant kingdom the Vegetabilia. When the name Plantae or plant is applied to a specific group of organisms or taxa , it usually refers to one of four concepts. From least to most inclusive, these four groupings are: There are about 382,000 accepted species of plants, of which
1581-709: The cell to move, change shape, or transport materials. The motor structures are microfilaments of actin and actin-binding proteins , including α- actinin , fimbrin , and filamin are present in submembranous cortical layers and bundles. Motor proteins of microtubules, dynein and kinesin , and myosin of actin filaments, provide dynamic character of the network. Many eukaryotes have long slender motile cytoplasmic projections, called flagella , or multiple shorter structures called cilia . These organelles are variously involved in movement, feeding, and sensation. They are composed mainly of tubulin , and are entirely distinct from prokaryotic flagella. They are supported by
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1632-404: The cell with structural support, protection, and a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell. The major polysaccharides making up the primary cell wall of land plants are cellulose , hemicellulose , and pectin . The cellulose microfibrils are linked together with hemicellulose, embedded in a pectin matrix. The most common hemicellulose in
1683-427: The complex transcription machinery, the membrane-sorting systems, the nuclear pore , and some enzymes in the biochemical pathways. Eukaryote cells include a variety of membrane-bound structures, together forming the endomembrane system. Simple compartments, called vesicles and vacuoles , can form by budding off other membranes. Many cells ingest food and other materials through a process of endocytosis , where
1734-622: The cytoplasm. Mitochondria are organelles in eukaryotic cells. The mitochondrion is commonly called "the powerhouse of the cell", for its function providing energy by oxidising sugars or fats to produce the energy-storing molecule ATP . Mitochondria have two surrounding membranes , each a phospholipid bilayer , the inner of which is folded into invaginations called cristae where aerobic respiration takes place. Mitochondria contain their own DNA , which has close structural similarities to bacterial DNA , from which it originated, and which encodes rRNA and tRNA genes that produce RNA which
1785-486: The development of forests in swampy environments dominated by clubmosses and horsetails, including some as large as trees, and the appearance of early gymnosperms , the first seed plants . The Permo-Triassic extinction event radically changed the structures of communities. This may have set the scene for the evolution of flowering plants in the Triassic (~ 200 million years ago ), with an adaptive radiation in
1836-406: The eukaryotes. Complex multicellular organisms, not counting the aggregation of amoebae to form slime molds , have evolved within only six eukaryotic lineages: animals , symbiomycotan fungi , brown algae , red algae , green algae , and land plants . Eukaryotes are grouped by genomic similarities, so that groups often lack visible shared characteristics. The defining feature of eukaryotes
1887-484: The eukaryotic evolutionary tree, core meiotic genes, and hence sex, were likely present in the common ancestor of eukaryotes. Species once thought to be asexual, such as Leishmania parasites, have a sexual cycle. Amoebae, previously regarded as asexual, may be anciently sexual; while present-day asexual groups could have arisen recently. In antiquity , the two lineages of animals and plants were recognized by Aristotle and Theophrastus . The lineages were given
1938-646: The form of chloroplasts which, like cyanobacteria, contain chlorophyll and produce organic compounds (such as glucose ) through photosynthesis . Others are involved in storing food. Although plastids probably had a single origin, not all plastid-containing groups are closely related. Instead, some eukaryotes have obtained them from others through secondary endosymbiosis or ingestion. The capture and sequestering of photosynthetic cells and chloroplasts, kleptoplasty , occurs in many types of modern eukaryotic organisms. The cytoskeleton provides stiffening structure and points of attachment for motor structures that enable
1989-409: The gametophyte is very small. Flowering plants reproduce sexually using flowers, which contain male and female parts: these may be within the same ( hermaphrodite ) flower, on different flowers on the same plant , or on different plants . The stamens create pollen , which produces male gametes that enter the ovule to fertilize the egg cell of the female gametophyte. Fertilization takes place within
2040-578: The great majority, some 283,000, produce seeds . The table below shows some species count estimates of different green plant (Viridiplantae) divisions . About 85–90% of all plants are flowering plants. Several projects are currently attempting to collect records on all plant species in online databases, e.g. the World Flora Online . Plants range in scale from single-celled organisms such as desmids (from 10 micrometres (μm) across) and picozoa (less than 3 μm across), to
2091-526: The land 1,200 million years ago , but it was not until the Ordovician , around 450 million years ago , that the first land plants appeared, with a level of organisation like that of bryophytes. However, fossils of organisms with a flattened thallus in Precambrian rocks suggest that multicellular freshwater eukaryotes existed over 1000 mya. Primitive land plants began to diversify in
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2142-412: The large water-filled central vacuole , chloroplasts , and the strong flexible cell wall , which is outside the cell membrane . Chloroplasts are derived from what was once a symbiosis of a non-photosynthetic cell and photosynthetic cyanobacteria . The cell wall, made mostly of cellulose , allows plant cells to swell up with water without bursting. The vacuole allows the cell to change in size while
2193-512: The largest trees ( megaflora ) such as the conifer Sequoia sempervirens (up to 120 metres (380 ft) tall) and the angiosperm Eucalyptus regnans (up to 100 m (325 ft) tall). The naming of plants is governed by the International Code of Nomenclature for algae, fungi, and plants and the International Code of Nomenclature for Cultivated Plants . The ancestors of land plants evolved in water. An algal scum formed on
2244-661: The late Silurian , around 420 million years ago . Bryophytes, club mosses, and ferns then appear in the fossil record. Early plant anatomy is preserved in cellular detail in an early Devonian fossil assemblage from the Rhynie chert . These early plants were preserved by being petrified in chert formed in silica-rich volcanic hot springs. By the end of the Devonian, most of the basic features of plants today were present, including roots, leaves and secondary wood in trees such as Archaeopteris . The Carboniferous period saw
2295-449: The outer membrane invaginates and then pinches off to form a vesicle. Some cell products can leave in a vesicle through exocytosis . The nucleus is surrounded by a double membrane known as the nuclear envelope , with nuclear pores that allow material to move in and out. Various tube- and sheet-like extensions of the nuclear membrane form the endoplasmic reticulum , which is involved in protein transport and maturation. It includes
2346-498: The physical or abiotic environment include temperature , water , light, carbon dioxide , and nutrients in the soil. Biotic factors that affect plant growth include crowding, grazing, beneficial symbiotic bacteria and fungi, and attacks by insects or plant diseases . Frost and dehydration can damage or kill plants. Some plants have antifreeze proteins , heat-shock proteins and sugars in their cytoplasm that enable them to tolerate these stresses . Plants are continuously exposed to
2397-538: The plant kingdom encompassed all living things that were not animals , and included algae and fungi . Definitions have narrowed since then; current definitions exclude the fungi and some of the algae. By the definition used in this article, plants form the clade Viridiplantae (green plants), which consists of the green algae and the embryophytes or land plants ( hornworts , liverworts , mosses , lycophytes , ferns , conifers and other gymnosperms , and flowering plants ). A definition based on genomes includes
2448-417: The primary cell wall is xyloglucan . Eukaryotes have a life cycle that involves sexual reproduction , alternating between a haploid phase, where only one copy of each chromosome is present in each cell, and a diploid phase, with two copies of each chromosome in each cell. The diploid phase is formed by fusion of two haploid gametes, such as eggs and spermatozoa , to form a zygote ; this may grow into
2499-498: The rough endoplasmic reticulum, covered in ribosomes which synthesize proteins; these enter the interior space or lumen. Subsequently, they generally enter vesicles, which bud off from the smooth endoplasmic reticulum. In most eukaryotes, these protein-carrying vesicles are released and further modified in stacks of flattened vesicles ( cisternae ), the Golgi apparatus . Vesicles may be specialized; for instance, lysosomes contain digestive enzymes that break down biomolecules in
2550-466: The smallest published genome is that of the carnivorous bladderwort ( Utricularia gibba) at 82 Mb (although it still encodes 28,500 genes) while the largest, from the Norway spruce ( Picea abies ), extends over 19.6 Gb (encoding about 28,300 genes). Plants are distributed almost worldwide. While they inhabit several biomes which can be divided into a multitude of ecoregions , only the hardy plants of
2601-503: Was expanded until Ernst Haeckel made it a kingdom encompassing all single-celled eukaryotes, the Protista , in 1866. The eukaryotes thus came to be seen as four kingdoms: The protists were at that time thought to be "primitive forms", and thus an evolutionary grade , united by their primitive unicellular nature. Understanding of the oldest branchings in the tree of life only developed substantially with DNA sequencing , leading to
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