33-431: A pteridophyte is a vascular plant (with xylem and phloem ) that reproduces by means of spores . Because pteridophytes produce neither flowers nor seeds , they are sometimes referred to as " cryptogams ", meaning that their means of reproduction is hidden. Ferns , horsetails (often treated as ferns), and lycophytes ( clubmosses , spikemosses , and quillworts ) are all pteridophytes. However, they do not form
66-534: A clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group , is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are
99-489: A life cycle with alternating , free-living gametophyte and sporophyte phases that are independent at maturity. The body of the sporophyte is well differentiated into roots, stem and leaves. The root system is always adventitious . The stem is either underground or aerial. The leaves may be microphylls or megaphylls . Their other common characteristics include vascular plant apomorphies (e.g., vascular tissue ) and land plant plesiomorphies (e.g., spore dispersal and
132-652: A monophyletic group because ferns (and horsetails) are more closely related to seed plants than to lycophytes. "Pteridophyta" is thus no longer a widely accepted taxon, but the term pteridophyte remains in common parlance, as do pteridology and pteridologist as a science and its practitioner, for example by the International Association of Pteridologists and the Pteridophyte Phylogeny Group . Pteridophytes (ferns and lycophytes) are free-sporing vascular plants that have
165-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
198-404: A clade but constitute a paraphyletic grade. Just as with bryophytes and spermatophytes (seed plants), the life cycle of pteridophytes involves alternation of generations . This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus , which produces gametes ). Pteridophytes differ from bryophytes in that
231-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
264-513: A consensus classification; These subclasses correspond to Smith's four classes, with Ophioglossidae corresponding to Psilotopsida. The two major groups previously included in Pteridophyta are phylogenetically related as follows: Lycopodiophyta Polypodiophyta – ferns Gymnospermae Angiospermae – flowering plants Pteridophytes consist of two separate but related classes, whose nomenclature has varied. The system put forward by
297-479: A higher taxonomic rank . Furthermore, within the Polypodiopsida, the largest grouping, a number of informal clades were recognised, including leptosporangiates, core leptosporangiates, polypods (Polypodiales), and eupolypods (including Eupolypods I and Eupolypods II ). In 2014 Christenhusz and Chase , summarising the known knowledge at that time, treated this group as two separate unrelated taxa in
330-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
363-622: A scientific replacement for "fern" (including Equisetaceae) and became established by Pryer et al. (2004). Christenhusz and Chase (2014) in their review of classification schemes provide a critique of this usage, which they discouraged as irrational. In fact the alternative name Filicopsida was already in use. By comparison "lycopod" or lycophyte (club moss) means wolf-plant. The term " fern ally " included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns ( Marsileaceae , Salviniaceae and Ceratopteris ). This
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#1732772833134396-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
429-499: Is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case,
462-566: Is an antiquated remnant of the obsolete scala naturae , and the term is generally considered to be unscientific. Botanists define vascular plants by three primary characteristics: Cavalier-Smith (1998) treated the Tracheophyta as a phylum or botanical division encompassing two of these characteristics defined by the Latin phrase "facies diploida xylem et phloem instructa" (diploid phase with xylem and phloem). One possible mechanism for
495-476: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
528-558: Is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate for non-leptosporangiate ferns. However both Infradivision and Moniliformopses are also invalid names under the International Code of Botanical Nomenclature . Ferns, despite forming a monophyletic clade , are formally only considered as four classes ( Psilotopsida ; Equisetopsida ; Marattiopsida ; Polypodiopsida ), 11 orders and 37 families , without assigning
561-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
594-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
627-860: Is supported by several molecular studies. Other researchers state that taking fossils into account leads to different conclusions, for example that the ferns (Pteridophyta) are not monophyletic. Hao and Xue presented an alternative phylogeny in 2013 for pre- euphyllophyte plants. † Horneophytaceae [REDACTED] † Cooksoniaceae † Aglaophyton † Rhyniopsida [REDACTED] † Catenalis † Aberlemnia † Hsuaceae † Renaliaceae [REDACTED] † Adoketophyton †? Barinophytopsida † Zosterophyllopsida † Hicklingia † Gumuia † Nothia Lycopodiopsida [REDACTED] † Zosterophyllum deciduum † Yunia † Eophyllophyton † Trimerophytopsida † Ibyka † Pauthecophyton † Cladoxylopsida Polypodiopsida [REDACTED] Clade In biological phylogenetics ,
660-508: The "true" tracheophytes, the eutracheophytes. † Aglaophyton † Horneophytopsida † Rhyniophyta Lycopodiophyta † Zosterophyllophyta † Cladoxylopsida Equisetopsida (horsetails) Marattiopsida Psilotopsida (whisk ferns and adders'-tongues) Pteridopsida (true ferns) † Progymnospermophyta Cycadophyta (cycads) Ginkgophyta (ginkgo) Gnetophyta Pinophyta (conifers) Magnoliophyta (flowering plants) † Pteridospermatophyta (seed ferns) This phylogeny
693-748: The Pteridophyte Phylogeny Group in 2016, PPG I , is: In addition to these living groups, several groups of pteridophytes are now extinct and known only from fossils . These groups include the Rhyniopsida , Zosterophyllopsida , Trimerophytopsida , the Lepidodendrales and the Progymnospermopsida . Modern studies of the land plants agree that seed plants emerged from pteridophytes more closer to ferns than lycophytes . Therefore, pteridophytes do not form
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#1732772833134726-399: The ability to grow independent roots, woody structure for support, and more branching. A proposed phylogeny of the vascular plants after Kenrick and Crane 1997 is as follows, with modification to the gymnosperms from Christenhusz et al. (2011a), Pteridophyta from Smith et al. and lycophytes and ferns by Christenhusz et al. (2011b) The cladogram distinguishes the rhyniophytes from
759-566: The absence of seeds ). Of the pteridophytes, ferns account for nearly 90% of the extant diversity. Smith et al. (2006), the first higher-level pteridophyte classification published in the molecular phylogenetic era, considered the ferns as monilophytes, as follows: where the monilophytes comprise about 9,000 species, including horsetails ( Equisetaceae ), whisk ferns (Psilotaceae), and all eusporangiate and all leptosporangiate ferns. Historically both lycophytes and monilophytes were grouped together as pteridophytes (ferns and fern allies) on
792-485: The basis of being spore-bearing ("seed-free"). In Smith's molecular phylogenetic study the ferns are characterised by lateral root origin in the endodermis , usually mesarch protoxylem in shoots, a pseudoendospore, plasmodial tapetum , and sperm cells with 30-1000 flagella . The term "moniliform" as in Moniliformopses and monilophytes means "bead-shaped" and was introduced by Kenrick and Crane (1997) as
825-451: The fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over
858-546: The group consists of a common ancestor with all its descendant branches. Rodents, for example, are a branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
891-590: The last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade"
924-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
957-473: The plant. They also have a specialized non-lignified tissue (the phloem ) to conduct products of photosynthesis . The group includes most land plants ( c. 300,000 accepted known species) other than mosses . Vascular plants include the clubmosses , horsetails , ferns , gymnosperms (including conifers ), and angiosperms ( flowering plants ). They are contrasted with nonvascular plants such as mosses and green algae . Scientific names for
990-421: The presumed evolution from emphasis on haploid generation to emphasis on diploid generation is the greater efficiency in spore dispersal with more complex diploid structures. Elaboration of the spore stalk enabled the production of more spores and the development of the ability to release them higher and to broadcast them further. Such developments may include more photosynthetic area for the spore-bearing structure,
1023-586: The sexes. Vascular plant Vascular plants (from Latin vasculum 'duct'), also called tracheophytes ( UK : / ˈ t r æ k iː ə ˌ f aɪ t s / , US : / ˈ t r eɪ k iː ə ˌ f aɪ t s / ) or collectively tracheophyta ( / ˌ t r eɪ k iː ˈ ɒ f ɪ t ə / ; from Ancient Greek τραχεῖα ἀρτηρία ( trakheîa artēría ) 'windpipe' and φυτά ( phutá ) 'plants'), are plants that have lignified tissues (the xylem ) for conducting water and minerals throughout
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1056-436: The sporophyte is branched and generally much larger and more conspicuous, and from seed plants in that both generations are independent and free-living. The sexuality of pteridophyte gametophytes can be classified as follows: These terms are not the same as monoecious and dioecious , which refer to whether a seed plant's sporophyte bears both male and female gametophytes, i. e., produces both pollen and seeds, or just one of
1089-463: The vascular plants group include Tracheophyta, Tracheobionta and Equisetopsida sensu lato . Some early land plants (the rhyniophytes ) had less developed vascular tissue; the term eutracheophyte has been used for all other vascular plants, including all living ones. Historically, vascular plants were known as " higher plants ", as it was believed that they were further evolved than other plants due to being more complex organisms. However, this
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