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Angiosperms are distinguished from the other seed-producing plants, the gymnosperms, by having flowers, xylem consisting of vessel elements instead of tracheids, endosperm within their seeds, and fruits that completely envelop the seeds.The ancestors of flowering plants diverged from the common ancestor of all living gymnosperms before the end of the Carboniferous, over 300 million years ago. In the Cretaceous, angiosperms diversified explosively, becoming the dominant group of plants across the planet.

Agriculture is almost entirely dependent on angiosperms, and a small number of flowering plant families supply nearly all plant-based food and livestock feed. Rice, maize, and wheat provide half of the world's calorie intake, and all three plants are cereals from the Poaceae family (colloquially known as grasses). Other families provide materials such as wood, paper and cotton, and supply numerous ingredients for traditional and modern medicines. Flowering plants are also commonly grown for decorative purposes, with certain flowers playing a significant role in many cultures.

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Considering their method of obtaining energy, some 99% of flowering plants are photosynthetic autotrophs, deriving their energy from sunlight and using it to create molecules such as sugars. The remainder are parasitic, whether on fungi like the orchids for part or all of their life-cycle,[17] or on other plants, either wholly like the broomrapes, Orobanche, or partially like the witchweeds, Striga.[18]

In terms of their environment, flowering plants are cosmopolitan, occupying a wide range of habitats on land, in fresh water and in the sea. On land, they are the dominant plant group in every habitat except for frigid moss-lichen tundra and coniferous forest.[19] The seagrasses in the Alismatales grow in marine environments, spreading with rhizomes that grow through the mud in sheltered coastal waters.[20]

Some specialised angiosperms are able to flourish in extremely acid or alkaline habitats. The sundews, many of which live in nutrient-poor acid bogs, are carnivorous plants, able to derive nutrients such as nitrate from the bodies of trapped insects.[21] Other flowers such as Gentiana verna, the spring gentian, are adapted to the alkaline conditions found on calcium-rich chalk and limestone, which give rise to often dry topographies such as limestone pavement.[22]

As for their growth habit, the flowering plants range from small, soft herbaceous plants, often living as annuals or biennials that set seed and die after one growing season,[23] to large perennial woody trees that may live for many centuries and grow to many metres in height. Some species grow tall without being self-supporting like trees by climbing on other plants in the manner of vines or lianas.[24]

The number of species of flowering plants is estimated to be in the range of 250,000 to 400,000.[25][26][27] This compares to around 12,000 species of moss[28] and 11,000 species of pteridophytes.[29] The APG system seeks to determine the number of families, mostly by molecular phylogenetics. In the 2009 APG III there were 415 families.[30] The 2016 APG IV added five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales and Vahliales), along with some new families, for a total of 64 angiosperm orders and 416 families.[1]

The diversity of flowering plants is not evenly distributed. Nearly all species belong to the eudicot (75%), monocot (23%), and magnoliid (2%) clades. The remaining five clades contain a little over 250 species in total; i.e. less than 0.1% of flowering plant diversity, divided among nine families. The 25 most species-rich of 443 families,[31] containing over 166,000 species between them in their APG circumscriptions, are:

Fossilised spores suggest that land plants (embryophytes) have existed for at least 475 million years.[45] However, angiosperms appear suddenly and in great diversity in the fossil record in the Early Cretaceous (~130 mya).[46][47] Claimed records of flowering plants prior to this are not widely accepted.[48] Molecular evidence suggests that the ancestors of angiosperms diverged from the gymnosperms during the late Devonian, about 365 million years ago.[49] The origin time of the crown group of flowering plants remains contentious.[50] By the Late Cretaceous, angiosperms appear to have dominated environments formerly occupied by ferns and gymnosperms. Large canopy-forming trees replaced conifers as the dominant trees close to the end of the Cretaceous, 66 million years ago.[51] The radiation of herbaceous angiosperms occurred much later.[52]

The flower may consist only of these parts, as in wind-pollinated plants like the willow, where each flower comprises only a few stamens or two carpels.[36] In insect- or bird-pollinated plants, other structures protect the sporophylls and attract pollinators. The individual members of these surrounding structures are known as sepals and petals (or tepals in flowers such as Magnolia where sepals and petals are not distinguishable from each other). The outer series (calyx of sepals) is usually green and leaf-like, and functions to protect the rest of the flower, especially the bud.[56][57] The inner series (corolla of petals) is, in general, white or brightly colored, is more delicate in structure, and attracts pollinators by colour, scent, and nectar.[58][59]

Most flowers are hermaphroditic, producing both pollen and ovules in the same flower, but some use other devices to reduce self-fertilization. Heteromorphic flowers have carpels and stamens of differing lengths, so animal pollinators cannot easily transfer pollen between them. Homomorphic flowers may use a biochemical self-incompatibility to discriminate between self and non-self pollen grains. Dioecious plants such as holly have male and female flowers on separate plants.[60] Monoecious plants have separate male and female flowers on the same plant; these are often wind-pollinated,[61] as in maize,[62] but include some insect-pollinated plants such as Cucurbita squashes.[63][64]

Agriculture is almost entirely dependent on angiosperms, which provide virtually all plant-based food and livestock feed. Much of this food derives from a small number of flowering plant families.[70] For instance, half of the world's calorie intake is supplied by just three plants - wheat, rice and maize.[71]

Flowering plants provide a diverse range of materials in the form of wood, paper, fibers such as cotton, flax, and hemp, medicines such as digoxin and opioids, and decorative and landscaping plants. Coffee and hot chocolate are beverages from flowering plants.[70]

Both real and fictitious plants play a wide variety of roles in literature and film.[74] Flowers are the subjects of many poems by poets such as William Blake, Robert Frost, and Rabindranath Tagore.[75] Bird-and-flower painting (Huaniaohua) is a kind of Chinese painting that celebrates the beauty of flowering plants.[76] Flowers have been used in literature to convey meaning by authors including William Shakespeare.[77] Flowers are used in a variety of art forms which arrange cut or living plants, such as bonsai, ikebana, and flower arranging. Ornamental plants have sometimes changed the course of history, as in tulipomania.[78] Many countries and regions have floral emblems; a survey of 70 of these found that the most popular flowering plant family for such emblems is Orchidaceae at 15.7% (11 emblems), followed by Fabaceae at 10% (7 emblems), and Asparagaceae, Asteraceae, and Rosaceae all at 5.7% (4 emblems each).[79]

Human impact on the environment has driven a range of species extinct and is threatening even more today. Multiple organizations such as IUCN and Royal Botanic Gardens, Kew suggest that around 40% of plant species are threatened with extinction.[81] The majority are threatened by habitat loss, but activities such as logging of wild timber trees and collection of medicinal plants, or the introduction of non-native invasive species, also play a role.[82] Relatively few plant diversity assessments currently consider climate change,[81] yet it is starting to impact plants as well: according to IPCC, about 3% of flowering plants are very likely to be driven extinct within a century at 2 C (3.6 F), and 10% at 3.2 C (5.8 F).[83] In worst-case scenarios, half of all tree species,[81] or of all plant species, may be driven extinct by climate change over that timeframe.[82]

Conservation in this context is the attempt to prevent extinction, whether in situ by protecting plants and their habitats in the wild, or ex situ in seed banks or as living plants.[82] Some 3000 botanic gardens around the world maintain living plants, including over 40% of the species known to be threatened, as an "insurance policy against extinction in the wild."[84] The United Nations' Global Strategy for Plant Conservation asserts that "without plants, there is no life".[85] It aims to "halt the continuing loss of plant diversity" throughout the world.[85]

Methods for identifying species by using short orthologous DNA sequences, known as "DNA barcodes," have been proposed and initiated to facilitate biodiversity studies, identify juveniles, associate sexes, and enhance forensic analyses. The cytochrome c oxidase 1 sequence, which has been found to be widely applicable in animal barcoding, is not appropriate for most species of plants because of a much slower rate of cytochrome c oxidase 1 gene evolution in higher plants than in animals. We therefore propose the nuclear internal transcribed spacer region and the plastid trnH-psbA intergenic spacer as potentially usable DNA regions for applying barcoding to flowering plants. The internal transcribed spacer is the most commonly sequenced locus used in plant phylogenetic investigations at the species level and shows high levels of interspecific divergence. The trnH-psbA spacer, although short ( approximately 450-bp), is the most variable plastid region in angiosperms and is easily amplified across a broad range of land plants. Comparison of the total plastid genomes of tobacco and deadly nightshade enhanced with trials on widely divergent angiosperm taxa, including closely related species in seven plant families and a group of species sampled from a local flora encompassing 50 plant families (for a total of 99 species, 80 genera, and 53 families), suggest that the sequences in this pair of loci have the potential to discriminate among the largest number of plant species for barcoding purposes. e24fc04721