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58-455: Though bryophytes were considered a paraphyletic group in recent years, almost all of the most recent phylogenetic evidence supports the monophyly of this group, as originally classified by Wilhelm Schimper in 1879. The term bryophyte comes from Ancient Greek βρύον ( brúon )  'tree moss, liverwort' and φυτόν ( phutón )  'plant'. The defining features of bryophytes are: Bryophytes exist in

116-479: A "single common ancestor" organism. Paraphyly is common in speciation , whereby a mother species (a paraspecies ) gives rise to a daughter species without itself becoming extinct. Research indicates as many as 20 percent of all animal species and between 20 and 50 percent of plant species are paraphyletic. Accounting for these facts, some taxonomists argue that paraphyly is a trait of nature that should be acknowledged at higher taxonomic levels. Cladists advocate

174-592: A cell nucleus, a plesiomorphy ) from its excluded descendants. Also, some systematists recognize paraphyletic groups as being involved in evolutionary transitions, the development of the first tetrapods from their ancestors for example. Any name given to these hypothetical ancestors to distinguish them from tetrapods—"fish", for example—necessarily picks out a paraphyletic group, because the descendant tetrapods are not included. Other systematists consider reification of paraphyletic groups to obscure inferred patterns of evolutionary history. The term " evolutionary grade "

232-461: A chemical that is poisonous to mice. Other bryophytes produce chemicals that are antifeedants which protect them from being eaten by slugs. When Phythium sphagnum is sprinkled on the soil of germinating seeds, it inhibits growth of "damping off fungus" which would otherwise kill young seedlings. Commercial Peat is a fuel produced from dried bryophytes, typically Sphagnum . Bryophytes' antibiotic properties and ability to retain water make them

290-407: A common ancestor are said to be monophyletic . A paraphyletic group is a monophyletic group from which one or more subsidiary clades (monophyletic groups) are excluded to form a separate group. Philosopher of science Marc Ereshefsky has argued that paraphyletic taxa are the result of anagenesis in the excluded group or groups. A cladistic approach normally does not grant paraphyletic assemblages

348-419: A group of dinosaurs (part of Diapsida ), both of which are "reptiles". Osteichthyes , bony fish, are paraphyletic when circumscribed to include only Actinopterygii (ray-finned fish) and Sarcopterygii (lungfish, etc.), and to exclude tetrapods ; more recently, Osteichthyes is treated as a clade, including the tetrapods. The " wasps " are paraphyletic, consisting of the narrow-waisted Apocrita without

406-420: A haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes , alternates with a diploid sporophyte, whose cells contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by meiosis , that grow into gametophytes. Bryophytes are gametophyte dominant, meaning that

464-439: A kind of lizard). Put another way, viviparity is a synapomorphy for Theria within mammals, and an autapomorphy for Eulamprus tympanum (or perhaps a synapomorphy, if other Eulamprus species are also viviparous). Groupings based on independently-developed traits such as these examples of viviparity represent examples of polyphyly , not paraphyly. The following list recapitulates a number of paraphyletic groups proposed in

522-400: A manner similar to lycophytes , ferns and other cryptogams . The sporophyte develops differently in the three groups. Both mosses and hornworts have a meristem zone where cell division occurs. In hornworts, the meristem starts at the base where the foot ends, and the division of cells pushes the sporophyte body upwards. In mosses, the meristem is located between the capsule and the top of

580-449: A monophyletic group: vascular plants hornworts mosses liverworts Consistent with this view, compared to other living land plants, all three lineages lack vascular tissue containing lignin and branched sporophytes bearing multiple sporangia. The prominence of the gametophyte in the life cycle is also a shared feature of the three bryophyte lineages (extant vascular plants are all sporophyte dominant). However, if this phylogeny

638-549: A more inclusive clade, it often makes sense to study the paraphyletic group that remains without considering the larger clade. For example, the Neogene evolution of the Artiodactyla (even-toed ungulates, like deer, cows, pigs and hippopotamuses - Cervidae , Bovidae , Suidae and Hippopotamidae , the families that contain these various artiodactyls, are all monophyletic groups) has taken place in environments so different from that of

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696-424: A phylogenetic species concept that does not consider species to exhibit the properties of monophyly or paraphyly, concepts under that perspective which apply only to groups of species. They consider Zander's extension of the "paraphyletic species" argument to higher taxa to represent a category error When the appearance of significant traits has led a subclade on an evolutionary path very divergent from that of

754-440: A thin layer of water is required on the surface of the plant to enable the movement of the flagellated sperm between gametophytes and the fertilization of an egg. Summary of the morphological characteristics of the gametophytes of the three groups of bryophytes: Summary of the morphological characteristics of the sporophytes of the three groups of bryophytes: Environmental Characteristics of bryophytes make them useful to

812-465: A useful packaging material for vegetables, flowers, and bulbs. Also, because of its antibiotic properties, Sphagnum was used as a surgical dressing in World War I. Paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic with respect to

870-489: A wide variety of habitats. They can be found growing in a range of temperatures (cold arctics and in hot deserts), elevations (sea-level to alpine), and moisture (dry deserts to wet rain forests). Bryophytes can grow where vascularized plants cannot because they do not depend on roots for uptake of nutrients from soil . Bryophytes can survive on rocks and bare soil. Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations . In each cycle,

928-433: Is allowed as a synonym of Magnoliopsida. Phylogenetic analysis indicates that the monocots are a development from a dicot ancestor. Excluding monocots from the dicots makes the latter a paraphyletic group. Among animals, several familiar groups are not, in fact, clades. The order Artiodactyla ( even-toed ungulates ) as traditionally defined is paraphyletic because it excludes Cetaceans (whales, dolphins, etc.). Under

986-441: Is between species in which the antheridia and archegonia occur on the same plant and those in which they occur on different plants. The term monoicous may be used where antheridia and archegonia occur on the same gametophyte and the term dioicous where they occur on different gametophytes. In seed plants , " monoecious " is used where flowers with anthers (microsporangia) and flowers with ovules (megasporangia) occur on

1044-455: Is correct, then the complex sporophyte of living vascular plants might have evolved independently of the simpler unbranched sporophyte present in bryophytes. Furthermore, this view implies that stomata evolved only once in plant evolution, before being subsequently lost in the liverworts. vascular plants hornworts mosses liverworts In this alternative view, the Setaphyta grouping

1102-406: Is known as the gne-pine hypothesis and looks like: (flowering plants) [REDACTED] Cycads [REDACTED] Ginkgo [REDACTED] Pinaceae (the pine family) [REDACTED] Gnetophytes [REDACTED] other conifers [REDACTED] However, the relationships between these groups should not be considered settled. Other classifications group all the seed plants in

1160-629: Is rather arbitrary, since the character states of common ancestors are inferences, not observations. These terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics . Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction. Related terms are stem group , chronospecies , budding cladogenesis, anagenesis, or 'grade' groupings. Paraphyletic groups are often relics from outdated hypotheses of phylogenic relationships from before

1218-410: Is retained, but hornworts instead are sister to vascular plants. (Another paraphyletic view involves hornworts branching out first.) Traditionally, when basing classifications on morphological characters, bryophytes have been distinguished by their lack of vascular structure. However, this distinction is problematic, firstly because some of the earliest-diverging (but now extinct) non-bryophytes, such as

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1276-548: Is said to be polyparaphyletic. The term received currency during the debates of the 1960s and 1970s accompanying the rise of cladistics , having been coined by zoologist Willi Hennig to apply to well-known taxa like Reptilia ( reptiles ), which is paraphyletic with respect to birds . Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor except for birds. Other commonly recognized paraphyletic groups include fish , monkeys , and lizards . The term paraphyly , or paraphyletic , derives from

1334-529: Is shown in the cladogram below: bryophytes "protracheophytes", such as Aglaophyton or Horneophyton tracheophytes or vascular plants There have probably been several different terrestrialization events, in which originally aquatic organisms colonized the land, just within the lineage of the Viridiplantae . Between 510–630 million years ago, however, land plants emerged within the green algae . Molecular phylogenetic studies conclude that bryophytes are

1392-482: Is sometimes used for paraphyletic groups. Moreover, the concepts of monophyly , paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species. Current phylogenetic hypotheses of tetrapod relationships imply that viviparity , the production of offspring without the external laying of a fertilized egg, developed independently in the lineages that led to humans ( Homo sapiens ) and southern water skinks ( Eulampus tympanum ,

1450-480: Is suspected that the extension was involved in anemophilous (wind) pollination . Runcaria sheds new light on the sequence of character acquisition leading to the seed. Runcaria has all of the qualities of seed plants except for a solid seed coat and a system to guide the pollen to the seed. Runcaria was followed shortly after by plants with a more condensed cupule, such as Spermasporites and Moresnetia . Seed-bearing plants had diversified substantially by

1508-503: The Cetacea (whales, dolphins, and porpoises) that the Artiodactyla are often studied in isolation even though the cetaceans are a descendant group. The prokaryote group is another example; it is paraphyletic because it is composed of two Domains (Eubacteria and Archaea) and excludes (the eukaryotes ). It is very useful because it has a clearly defined and significant distinction (absence of

1566-562: The Famennian , the last stage of the Devonian. Examples include Elkinsia , Xenotheca , Archaeosperma , " Hydrasperma ", Aglosperma , and Warsteinia . Some of these Devonian seeds are now classified within the order Lyginopteridales . Seed-bearing plants are a clade within the vascular plants (tracheophytes). The spermatophytes were traditionally divided into angiosperms , or flowering plants, and gymnosperms , which includes

1624-569: The ICN ) abandoned consideration of bacterial nomenclature in 1975; currently, prokaryotic nomenclature is regulated under the ICNB with a starting date of 1 January 1980 (in contrast to a 1753 start date under the ICBN/ICN). Among plants, dicotyledons (in the traditional sense) are paraphyletic because the group excludes monocotyledons . "Dicotyledon" has not been used as a botanic classification for decades, but

1682-481: The Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts). However, it has been proposed that these clades are de-ranked to the classes Marchantiopsida, Bryopsida, and Anthocerotopsida, respectively. There is now strong evidence that the liverworts and mosses belong to a monophyletic clade, called Setaphyta . The favored model, based on amino acids phylogenies, indicates bryophytes as

1740-503: 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 the angiosperms radiated. A whole genome duplication event in the ancestor of seed plants occurred about 319  million years ago . This gave rise to a series of evolutionary changes that resulted in

1798-638: The ants and bees . The sawflies ( Symphyta ) are similarly paraphyletic, forming all of the Hymenoptera except for the Apocrita, a clade deep within the sawfly tree. Crustaceans are not a clade because the Hexapoda (insects) are excluded. The modern clade that spans all of them is the Tetraconata . One of the goals of modern taxonomy over the past fifty years has been to eliminate paraphyletic "groups", such as

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1856-450: The horneophytes , did not have true vascular tissue, and secondly because many mosses have well-developed water-conducting vessels. A more useful distinction may lie in the structure of their sporophytes . In bryophytes, the sporophyte is a simple unbranched structure with a single spore-forming organ ( sporangium ), whereas in all other land plants, the polysporangiophytes , the sporophyte is branched and carries many sporangia. The contrast

1914-407: The archegonia. Mature sporophytes remain attached to the gametophyte. They consist of a stalk called a seta and a single sporangium or capsule. Inside the sporangium, haploid spores are produced by meiosis . These are dispersed, most commonly by wind, and if they land in a suitable environment can develop into a new gametophyte. Thus bryophytes disperse by a combination of swimming sperm and spores, in

1972-403: The bryophytes are monophyletic after all. Since then, partially thanks to a proliferation of genomic and transcriptomic datasets, almost all phylogenetics studies based on nuclear and chloroplastic sequences have concluded that the bryophytes form a monophyletic group. Nevertheless, phylogenies based on mitochondrial sequences fail to support the monophyletic view. The three bryophyte clades are

2030-425: The earliest diverging lineages of the extant land plants. They provide insights into the migration of plants from aquatic environments to land. A number of physical features link bryophytes to both land plants and aquatic plants. Green algae, bryophytes and vascular plants all have chlorophyll a and b, and the chloroplast structures are similar. Like green algae and land plants, bryophytes also produce starch stored in

2088-512: The environment. Depending on the specific plant texture, bryophytes have been shown to help improve the water retention and air space within soil. Bryophytes are used in pollution studies to indicate soil pollution (such as the presence of heavy metals), air pollution, and UV-B radiation. Gardens in Japan are designed with moss to create peaceful sanctuaries. Some bryophytes have been found to produce natural pesticides. The liverwort, Plagiochila, produces

2146-450: The examples given here, from formal classifications. Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification. Some articulations of the phylogenetic species concept require species to be monophyletic, but paraphyletic species are common in nature, to the extent that they do not have a single common ancestor. Indeed, for sexually reproducing taxa, no species has

2204-411: The excluded subgroups. In contrast, a monophyletic grouping (a clade ) includes a common ancestor and all of its descendants. The terms are commonly used in phylogenetics (a subfield of biology ) and in the tree model of historical linguistics . Paraphyletic groups are identified by a combination of synapomorphies and symplesiomorphies . If many subgroups are missing from the named group, it

2262-473: The fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor. By comparison, the term polyphyly , or polyphyletic , uses the Ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. Groups that include all the descendants of

2320-655: 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 the Greek φανερός ( phanerós ), meaning "visible", in contrast to the term "cryptogam" or " cryptogamae " (from Ancient Greek κρυπτός (kruptós)  'hidden'), together with the suffix γαμέω ( gaméō ), meaning "to marry". These terms distinguish those plants with hidden sexual organs (cryptogamae) from those with visible ones (phanerogamae). The extant spermatophytes form five divisions,

2378-401: The first four of which are classified as gymnosperms , plants that have unenclosed, "naked seeds": The fifth extant division is the flowering plants , also known as angiosperms or magnoliophytes, the largest and most diverse group of spermatophytes: In addition to the five living taxa listed above, the fossil record contains evidence of many extinct taxa of seed plants, among those: By

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2436-483: The gametophytes, sometimes at the tips of shoots, in the axils of leaves or hidden under thalli. Some bryophytes, such as the liverwort Marchantia , create elaborate structures to bear the gametangia that are called gametangiophores. Sperm are flagellated and must swim from the antheridia that produce them to archegonia which may be on a different plant. Arthropods can assist in transfer of sperm. Fertilized eggs become zygotes, which develop into sporophyte embryos inside

2494-431: The gnetophytes, cycads, ginkgo, and conifers. Older morphological studies believed in a close relationship between the gnetophytes and the angiosperms, in particular based on vessel elements . However, molecular studies (and some more recent morphological and fossil papers) have generally shown a clade of gymnosperms , with the gnetophytes in or near the conifers. For example, one common proposed set of relationships

2552-452: The island of Taiwan . Seed plant A seed plant or spermatophyte ( lit.   ' seed plant ' ; from Ancient Greek σπέρματος ( spérmatos )  'seed' and φυτόν (phytón)  'plant'), also known as 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

2610-605: The literature, and provides the corresponding monophyletic taxa. The concept of paraphyly has also been applied to historical linguistics , where the methods of cladistics have found some utility in comparing languages. For instance, the Formosan languages form a paraphyletic group of the Austronesian languages because they consist of the nine branches of the Austronesian family that are not Malayo-Polynesian and are restricted to

2668-510: The liverworts). G.M. Smith placed this group between Algae and Pteridophyta . Although a 2005 study supported this traditional monophyletic view, by 2010 a broad consensus had emerged among systematists that bryophytes as a whole are not a natural group (i.e., are paraphyletic ). However, a 2014 study concluded that these previous phylogenies, which were based on nucleic acid sequences, were subject to composition biases, and that, furthermore, phylogenies based on amino acid sequences suggested that

2726-532: The more prominent, longer-lived plant is the haploid gametophyte. The diploid sporophytes appear only occasionally and remain attached to and nutritionally dependent on the gametophyte. In bryophytes, the sporophytes are always unbranched and produce a single sporangium (spore producing capsule), but each gametophyte can give rise to several sporophytes at once. Liverworts, mosses and hornworts spend most of their lives as gametophytes. Gametangia (gamete-producing organs), archegonia and antheridia , are produced on

2784-423: The moss genus Bryum . Traditionally, all living land plants without vascular tissues were classified in a single taxonomic group, often a division (or phylum). The term "Bryophyta" was first suggested by Braun in 1864. As early as 1879, the term Bryophyta was used by German bryologist Wilhelm Schimper to describe a group containing all three bryophyte clades (though at the time, hornworts were considered part of

2842-413: The origin of modern seed plants. A middle Devonian (385-million-year-old) precursor to seed plants from Belgium has been identified predating the earliest seed plants by about 20 million years. Runcaria , small and radially symmetrical, is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the mutlilobed integument . It

2900-526: The plastids and contain cellulose in their walls. Distinct adaptations observed in bryophytes have allowed plants to colonize Earth's terrestrial environments. To prevent desiccation of plant tissues in a terrestrial environment, a waxy cuticle covering the soft tissue of the plant may be present, providing protection. In hornworts and mosses, stomata provide gas exchange between the atmosphere and an internal intercellular space system. The development of gametangia provided further protection specifically for gametes,

2958-675: The ranks of the ICZN Code , the two taxa are separate orders. Molecular studies, however, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetaceans the Artiodactyls are paraphyletic. The class Reptilia is paraphyletic because it excludes birds (class Aves ). Under a traditional classification, these two taxa are separate classes. However birds are sister taxon to

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3016-563: The rise of cladistics. The prokaryotes (single-celled life forms without cell nuclei) are a paraphyletic grouping, because they exclude the eukaryotes , a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria. The prokaryote/eukaryote distinction was proposed by Edouard Chatton in 1937 and was generally accepted after being adopted by Roger Stanier and C.B. van Niel in 1962. The botanical code (the ICBN, now

3074-479: The same sporophyte and " dioecious " where they occur on different sporophytes. These terms occasionally may be used instead of "monoicous" and "dioicous" to describe bryophyte gametophytes. "Monoecious" and "monoicous" are both derived from the Greek for "one house", "dioecious" and "dioicous" from the Greek for two houses. The use of the "-oicy" terminology refers to the gametophyte sexuality of bryophytes as distinct from

3132-605: The sporophyte sexuality of seed plants. Monoicous plants are necessarily hermaphroditic, meaning that the same plant produces gametes of both sexes. The exact arrangement of the antheridia and archegonia in monoicous plants varies. They may be borne on different shoots (autoicous), on the same shoot but not together in a common structure (paroicous or paroecious), or together in a common "inflorescence" (synoicous or synoecious). Dioicous plants are unisexual , meaning that an individual plant has only one sex. All four patterns (autoicous, paroicous, synoicous and dioicous) occur in species of

3190-424: The stalk (seta), and produces cells downward, elongating the stalk and elevating the capsule. In liverworts the meristem is absent and the elongation of the sporophyte is caused almost exclusively by cell expansion. The arrangement of antheridia and archegonia on an individual bryophyte plant is usually constant within a species, although in some species it may depend on environmental conditions. The main division

3248-460: The status of "groups", nor does it reify them with explanations, as in cladistics they are not seen as the actual products of evolutionary events. A group whose identifying features evolved convergently in two or more lineages is polyphyletic (Greek πολύς [ polys ], "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic. Empirically, the distinction between polyphyletic groups and paraphyletic groups

3306-477: The two Ancient Greek words παρά ( pará ), meaning "beside, near", and φῦλον ( phûlon ), meaning "genus, species", and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are left apart from all other descendants of a unique common ancestor. Conversely, the term monophyly , or monophyletic , builds on the Ancient Greek prefix μόνος ( mónos ), meaning "alone, only, unique", and refers to

3364-488: The zygote and the developing sporophyte. The bryophytes and vascular plants ( embryophytes ) also have embryonic development which is not seen in green algae. While bryophytes have no truly vascularized tissue, they do have organs that are specialized for transport of water and other specific functions, analogous for example to the functions of leaves and stems in vascular land plants. Bryophytes depend on water for reproduction and survival. In common with ferns and lycophytes ,

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