Mšeno ( Czech pronunciation: [ˈm̩ʃɛno] ; German : Wemschen ) is a town in Mělník District the Central Bohemian Region of the Czech Republic . It has about 1,400 inhabitants. The historic town centre is well preserved and is protected by law as an urban monument zone .
108-512: The villages of Brusné 2.díl, Hradsko, Olešno, Ráj, Romanov, Sedlec, Skramouš and Vojtěchov are administrative parts of Mšeno. The name is derived from the Czech word mech , i.e. ' moss '. Mšeno is located about 14 kilometres (9 mi) northeast of Mělník and 37 km (23 mi) north of Prague . It lies on the border between the Jizera Table and Ralsko Uplands . The highest point
216-535: A ploidy series , featuring diploid ( X. tropicalis , 2n=20), tetraploid ( X. laevis , 4n=36), octaploid ( X. wittei , 8n=72), and dodecaploid ( X. ruwenzoriensis , 12n=108) species. Over evolutionary time scales in which chromosomal polymorphisms accumulate, these changes become less apparent by karyotype – for example, humans are generally regarded as diploid, but the 2R hypothesis has confirmed two rounds of whole genome duplication in early vertebrate ancestors. Ploidy can also vary between individuals of
324-520: A stem that may be branched or unbranched and has only a limited role in conducting water and nutrients. Although some species have conducting tissues, these are generally poorly developed and structurally different from similar tissue found in vascular plants . Mosses do not have seeds and after fertilisation develop sporophytes with unbranched stalks topped with single capsules containing spores . They are typically 0.2–10 cm (0.1–3.9 in) tall, though some species are much larger. Dawsonia ,
432-417: A syncytium , though usually the ploidy of each nucleus is described individually. For example, a fungal dikaryon with two separate haploid nuclei is distinguished from a diploid cell in which the chromosomes share a nucleus and can be shuffled together. It is possible on rare occasions for ploidy to increase in the germline , which can result in polyploid offspring and ultimately polyploid species. This
540-675: A zygote with n pairs of chromosomes, i.e. 2 n chromosomes in total. The chromosomes in each pair, one of which comes from the sperm and one from the egg, are said to be homologous . Cells and organisms with pairs of homologous chromosomes are called diploid. For example, most animals are diploid and produce haploid gametes. During meiosis , sex cell precursors have their number of chromosomes halved by randomly "choosing" one member of each pair of chromosomes, resulting in haploid gametes. Because homologous chromosomes usually differ genetically, gametes usually differ genetically from one another. All plants and many fungi and algae switch between
648-467: A chromosome copy number of 1 to 4, and that number is commonly fractional, counting portions of the chromosome partly replicated at a given time. This is because under exponential growth conditions the cells are able to replicate their DNA faster than they can divide. In ciliates, the macronucleus is called ampliploid , because only part of the genome is amplified. Mixoploidy is the case where two cell lines, one diploid and one polyploid, coexist within
756-407: A few years of exposure to wind and rain. Materials which are porous and moisture retentive, such as brick , wood , and certain coarse concrete mixtures, are hospitable to moss. Surfaces can also be prepared with acidic substances, including buttermilk , yogurt , urine , and gently puréed mixtures of moss samples, water and ericaceous compost . In the cool, humid, cloudy Pacific Northwest , moss
864-926: A garden weed in Vancouver and Seattle areas; Bryum argenteum , the cosmopolitan sidewalk moss, and Ceratodon purpureus , red roof moss, another cosmopolitan species. A few species are wholly aquatic, such as Fontinalis antipyretica , common water moss; and others such as Sphagnum inhabit bogs, marshes and very slow-moving waterways. Such aquatic or semi-aquatic mosses can greatly exceed the normal range of lengths seen in terrestrial mosses. Individual plants 20–30 cm (8–12 in) or more long are common in Sphagnum species for example. But even aquatic species of moss and other bryophytes needs their mature capsules to be exposed to air by seta elongation or seasonal lowering of water level to be able to reproduce. Wherever they occur, mosses require liquid water for at least part of
972-424: A germ cell with an uneven number of chromosomes undergoes meiosis, the chromosomes cannot be evenly divided between the daughter cells, resulting in aneuploid gametes. Triploid organisms, for instance, are usually sterile. Because of this, triploidy is commonly exploited in agriculture to produce seedless fruit such as bananas and watermelons. If the fertilization of human gametes results in three sets of chromosomes,
1080-408: A haploid spore that germinates to produce a protonema ( pl. protonemata), which is either a mass of thread-like filaments or thalloid (flat and thallus-like). Massed moss protonemata typically look like a thin green felt, and may grow on damp soil, tree bark, rocks, concrete, or almost any other reasonably stable surface. This is a transitory stage in the life of a moss, but from the protonema grows
1188-629: A haploid and a diploid state, with one of the stages emphasized over the other. This is called alternation of generations . Most fungi and algae are haploid during the principal stage of their life cycle, as are some primitive plants like mosses . More recently evolved plants, like the gymnosperms and angiosperms , spend the majority of their life cycle in the diploid stage. Most animals are diploid, but male bees , wasps , and ants are haploid organisms because they develop from unfertilized, haploid eggs, while females (workers and queens) are diploid, making their system haplodiploid . In some cases there
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#17328012815061296-536: A member of the Polytrichidae is probably Dawsonia superba , a native to New Zealand and other parts of Australasia . The fossil record of moss is sparse, due to their soft-walled and fragile nature. Unambiguous moss fossils have been recovered from as early as the Permian of Antarctica and Russia, and a case has been made for Carboniferous mosses. It has further been claimed that tube-like fossils from
1404-451: A number of chromosomes that is an exact multiple of the number of chromosomes in a normal gamete; and having any other number, respectively. For example, a person with Turner syndrome may be missing one sex chromosome (X or Y), resulting in a (45,X) karyotype instead of the usual (46,XX) or (46,XY). This is a type of aneuploidy and cells from the person may be said to be aneuploid with a (diploid) chromosome complement of 45. The term ploidy
1512-414: A partner that contains the same, or similar, genetic information. By contrast, mosses and other bryophytes have only a single set of chromosomes and so are haploid (i.e. each chromosome exists in a unique copy within the cell). There is a period in the moss life cycle when they do have a double set of paired chromosomes, but this happens only during the sporophyte stage. The moss life-cycle starts with
1620-425: A process called endoreduplication , where duplication of the genome occurs without mitosis (cell division). The extreme in polyploidy occurs in the fern genus Ophioglossum , the adder's-tongues, in which polyploidy results in chromosome counts in the hundreds, or, in at least one case, well over one thousand. It is possible for polyploid organisms to revert to lower ploidy by haploidisation . Polyploidy
1728-438: A scent-mediated relationship analogous to the plant-pollinator relationship found in many seed plants. The stinkmoss species Splachnum sphaericum develops insect pollination further by attracting flies to its sporangia with a strong smell of carrion, and providing a strong visual cue in the form of red-coloured swollen collars beneath each spore capsule. Flies attracted to the moss carry its spores to fresh herbivore dung, which
1836-412: A similar purpose. Mosses can be either dioicous (compare dioecious in seed plants) or monoicous (compare monoecious ). In dioicous mosses, male and female sex organs are borne on different gametophyte plants. In monoicous (also called autoicous) mosses, both are borne on the same plant. In the presence of water, sperm from the antheridia swim to the archegonia and fertilisation occurs, leading to
1944-401: A single nucleus rather than in the cell as a whole. Because in most situations there is only one nucleus per cell, it is commonplace to speak of the ploidy of a cell, but in cases in which there is more than one nucleus per cell, more specific definitions are required when ploidy is discussed. Authors may at times report the total combined ploidy of all nuclei present within the cell membrane of
2052-437: A single chromosome and diploid individuals have two chromosomes. In Entamoeba , the ploidy level varies from 4 n to 40 n in a single population. Alternation of generations occurs in most plants, with individuals "alternating" ploidy level between different stages of their sexual life cycle. In large multicellular organisms, variations in ploidy level between different tissues, organs, or cell lineages are common. Because
2160-495: A single copy of each chromosome – that is, one and only one set of chromosomes. In this case, the nucleus of a eukaryotic cell is said to be haploid only if it has a single set of chromosomes , each one not being part of a pair. By extension a cell may be called haploid if its nucleus has one set of chromosomes, and an organism may be called haploid if its body cells (somatic cells) have one set of chromosomes per cell. By this definition haploid therefore would not be used to refer to
2268-484: A single parent, without the involvement of gametes and fertilization, and all the offspring are genetically identical to each other and to the parent, including in chromosome number. The parents of these vegetative clones may still be capable of producing haploid gametes in preparation for sexual reproduction, but these gametes are not used to create the vegetative offspring by this route. Some eukaryotic genome-scale or genome size databases and other sources which may list
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#17328012815062376-490: Is 24. The monoploid number equals the total chromosome number divided by the ploidy level of the somatic cells: 48 chromosomes in total divided by a ploidy level of 4 equals a monoploid number of 12. Hence, the monoploid number (12) and haploid number (24) are distinct in this example. However, commercial potato crops (as well as many other crop plants) are commonly propagated vegetatively (by asexual reproduction through mitosis), in which case new individuals are produced from
2484-402: Is 7. The gametes of common wheat are considered to be haploid, since they contain half the genetic information of somatic cells, but they are not monoploid, as they still contain three complete sets of chromosomes ( n = 3 x ). In the case of wheat, the origin of its haploid number of 21 chromosomes from three sets of 7 chromosomes can be demonstrated. In many other organisms, although
2592-519: Is a back-formation from haploidy and diploidy . "Ploid" is a combination of Ancient Greek -πλόος (-plóos, "-fold") and -ειδής (- eidḗs ), from εἶδος ( eîdos , "form, likeness"). The principal meaning of the Greek word ᾰ̔πλόος (haplóos) is "single", from ἁ- (ha-, "one, same"). διπλόος ( diplóos ) means "duplex" or "two-fold". Diploid therefore means "duplex-shaped" (compare "humanoid", "human-shaped"). Polish-German botanist Eduard Strasburger coined
2700-413: Is a characteristic of the bacterium Deinococcus radiodurans and of the archaeon Halobacterium salinarum . These two species are highly resistant to ionizing radiation and desiccation , conditions that induce DNA double-strand breaks. This resistance appears to be due to efficient homologous recombinational repair. Depending on growth conditions, prokaryotes such as bacteria may have
2808-412: Is an important evolutionary mechanism in both plants and animals and is known as a primary driver of speciation . As a result, it may become desirable to distinguish between the ploidy of a species or variety as it presently breeds and that of an ancestor. The number of chromosomes in the ancestral (non-homologous) set is called the monoploid number ( x ), and is distinct from the haploid number ( n ) in
2916-462: Is associated with a 14% lower risk of being endangered, and a 20% greater chance of being invasive. Polyploidy may be associated with increased vigor and adaptability. Some studies suggest that selection is more likely to favor diploidy in host species and haploidy in parasite species. However, polyploidization is associated with an increase in transposable element content and relaxed purifying selection on recessive deleterious alleles. When
3024-435: Is deliberately encouraged to grow under aesthetic principles exemplified by Japanese gardening . In old temple gardens, moss can carpet a forest scene. Moss is thought to add a sense of calm, age, and stillness to a garden scene. Moss is also used in bonsai to cover the soil and enhance the impression of age. Rules of cultivation are not widely established. Moss collections are quite often begun using samples transplanted from
3132-448: Is disrupted by fungal chitin . Galotto et al. , 2020 applied chitooctaose and found that tips detected and responded to this chitin derivative by changing gene expression . They concluded that this defense response was probably conserved from the most recent common ancestor of bryophytes and tracheophytes . Orr et al. , 2020 found that the microtubules of growing tip cells were structurally similar to F-actin and served
3240-525: Is evidence that the n chromosomes in a haploid set have resulted from duplications of an originally smaller set of chromosomes. This "base" number – the number of apparently originally unique chromosomes in a haploid set – is called the monoploid number , also known as basic or cardinal number , or fundamental number . As an example, the chromosomes of common wheat are believed to be derived from three different ancestral species, each of which had 7 chromosomes in its haploid gametes. The monoploid number
3348-545: Is famous for its moss garden. The moss garden was created by removing shrubby underbrush and herbaceous groundcovers, thinning trees, and allowing mosses to fill in naturally. Mosses are sometimes used in green roofs . Advantages of mosses over higher plants in green roofs include reduced weight loads, increased water absorption, no fertilizer requirements, and high drought tolerance. Since mosses do not have true roots, they require less planting medium than higher plants with extensive root systems. With proper species selection for
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3456-471: Is faster than diploid under high nutrient conditions. The NLH is also tested in haploid, diploid, and polyploid fungi by Gerstein et al. 2017. This result is also more complex: On the one hand, under phosphorus and other nutrient limitation, lower ploidy is selected as expected. However under normal nutrient levels or under limitation of only nitrogen , higher ploidy was selected. Thus the NLH – and more generally,
3564-446: Is positively associated with the presence of dwarf males in several phyllodioicous species. Dwarf males occur in several unrelated lineages and may be more common than previously thought. For example, it is estimated that between one quarter and half of all dioicous pleurocarps have dwarf males. The moss Physcomitrium patens has been used as a model organism to study how plants repair damage to their DNA, especially
3672-504: Is sometimes allowed to grow naturally as a moss lawn , one that needs little or no mowing, fertilizing or watering. In this case, grass is considered to be the weed. Landscapers in the Seattle area sometimes collect boulders and downed logs growing mosses for installation in gardens and landscapes. Woodland gardens in many parts of the world can include a carpet of natural mosses. The Bloedel Reserve on Bainbridge Island, Washington State,
3780-534: Is the dominant phase of the life cycle . This contrasts with the pattern in all vascular plants ( seed plants and pteridophytes ), where the diploid sporophyte generation is dominant. Mosses reproduce using spores , not seeds , and have no flowers. Moss gametophytes have stems which may be simple or branched and upright (acrocarp) or prostrate (pleurocarp). The early divergent classes Takakiopsida, Sphagnopsida, Andreaeopsida and Andreaeobryopsida either lack stomata or have pseudostomata that do not form pores. In
3888-545: Is the favoured habitat of the species of this genus. In many mosses, e.g., Ulota phyllantha , green vegetative structures called gemmae are produced on leaves or branches, which can break off and form new plants without the need to go through the cycle of fertilization. This is a means of asexual reproduction , and the genetically identical units can lead to the formation of clonal populations. Moss dwarf males (also known as nannandry or phyllodioicy ) originate from wind-dispersed male spores that settle and germinate on
3996-487: Is the hill Uhelný vrch at 451 m (1,480 ft) above sea level. A large part of the municipal territory lies in the Kokořínsko – Máchův kraj Protected Landscape Area. The Slavic people settled the town area probably in the 5th–6th centuries. The first written mention of Mšeno is from 1306, in a document signed by Wenceslaus III awarding the then-village to aristocrat Hynek of Dubá. He, and his son after him, ensured
4104-572: Is the simplest to illustrate in diagrams of genetics concepts. But this definition also allows for haploid gametes with more than one set of chromosomes. As given above, gametes are by definition haploid, regardless of the actual number of sets of chromosomes they contain. An organism whose somatic cells are tetraploid (four sets of chromosomes), for example, will produce gametes by meiosis that contain two sets of chromosomes. These gametes might still be called haploid even though they are numerically diploid. An alternative usage defines "haploid" as having
4212-426: Is the state in which the chromosomes are paired and can undergo meiosis. The zygoid state of a species may be diploid or polyploid. In the azygoid state the chromosomes are unpaired. It may be the natural state of some asexual species or may occur after meiosis. In diploid organisms the azygoid state is monoploid. (See below for dihaploidy.) In the strictest sense, ploidy refers to the number of sets of chromosomes in
4320-731: Is the state where all cells have multiple sets of chromosomes beyond the basic set, usually 3 or more. Specific terms are triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), octoploid (8 sets), nonaploid (9 sets), decaploid (10 sets), undecaploid (11 sets), dodecaploid (12 sets), tridecaploid (13 sets), tetradecaploid (14 sets), etc. Some higher ploidies include hexadecaploid (16 sets), dotriacontaploid (32 sets), and tetrahexacontaploid (64 sets), though Greek terminology may be set aside for readability in cases of higher ploidy (such as "16-ploid"). Polytene chromosomes of plants and fruit flies can be 1024-ploid. Ploidy of systems such as
4428-402: Is thus 7 and the haploid number is 3 × 7 = 21. In general n is a multiple of x . The somatic cells in a wheat plant have six sets of 7 chromosomes: three sets from the egg and three sets from the sperm which fused to form the plant, giving a total of 42 chromosomes. As a formula, for wheat 2 n = 6 x = 42, so that the haploid number n is 21 and the monoploid number x
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4536-417: Is well established in this original sense, but it has also been used for doubled monoploids or doubled haploids , which are homozygous and used for genetic research. Euploidy ( Greek eu , "true" or "even") is the state of a cell or organism having one or more than one set of the same set of chromosomes, possibly excluding the sex-determining chromosomes . For example, most human cells have 2 of each of
4644-558: The Silurian are the macerated remains of moss calyptræ . Mosses also appear to evolve 2–3 times slower than ferns, gymnosperms and angiosperms . Recent research shows that ancient moss could explain why the Ordovician ice ages occurred. When the ancestors of today's moss started to spread on land 470 million years ago, they absorbed CO 2 from the atmosphere and extracted minerals by secreting organic acids that dissolved
4752-475: The Southern Hemisphere . Some naturalists feel that mosses grow on the damper side of trees and rocks. In some cases, such as sunny climates in temperate northern latitudes, this will be the shaded north side of the tree or rock. On steep slopes, it may be the uphill side. For mosses that grow on tree branches, this is generally the upper side of the branch on horizontally growing sections or near
4860-408: The gametophore ("gamete-bearer") that is structurally differentiated into stems and leaves. A single mat of protonemata may develop several gametophore shoots, resulting in a clump of moss. From the tips of the gametophore stems or branches develop the sex organs of the mosses. The female organs are known as archegonia ( sing. archegonium ) and are protected by a group of modified leaves known as
4968-423: The monoploid number ( x ). The haploid number ( n ) refers to the total number of chromosomes found in a gamete (a sperm or egg cell produced by meiosis in preparation for sexual reproduction). Under normal conditions, the haploid number is exactly half the total number of chromosomes present in the organism's somatic cells, with one paternal and maternal copy in each chromosome pair. For diploid organisms,
5076-410: The polysporangiophytes , which include all vascular plants. The spore-producing sporophytes (i.e. the diploid multicellular generation) are short-lived and usually capable of photosynthesis, but are dependent on the gametophyte for water supply and most or all of its nutrients. Also, in the majority of mosses, the spore-bearing capsule enlarges and matures after its stalk elongates, while in liverworts
5184-425: The salivary gland , elaiosome , endosperm , and trophoblast can exceed this, up to 1048576-ploid in the silk glands of the commercial silkworm Bombyx mori . The chromosome sets may be from the same species or from closely related species. In the latter case, these are known as allopolyploids (or amphidiploids, which are allopolyploids that behave as if they were normal diploids). Allopolyploids are formed from
5292-453: The 23 homologous monoploid chromosomes, for a total of 46 chromosomes. A human cell with one extra set of the 23 normal chromosomes (functionally triploid) would be considered euploid. Euploid karyotypes would consequentially be a multiple of the haploid number , which in humans is 23. Aneuploidy is the state where one or more individual chromosomes of a normal set are absent or present in more than their usual number of copies (excluding
5400-407: The 23 homologous pairs of chromosomes that humans normally have. This results in two homologous pairs within each of the 23 homologous pairs, providing a full complement of 46 chromosomes. This total number of individual chromosomes (counting all complete sets) is called the chromosome number or chromosome complement . The number of chromosomes found in a single complete set of chromosomes is called
5508-572: The absence or presence of complete sets, which is considered euploidy). Unlike euploidy, aneuploid karyotypes will not be a multiple of the haploid number. In humans, examples of aneuploidy include having a single extra chromosome (as in Down syndrome , where affected individuals have three copies of chromosome 21) or missing a chromosome (as in Turner syndrome , where affected individuals have only one sex chromosome). Aneuploid karyotypes are given names with
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#17328012815065616-502: The atmosphere. Small organisms feeding on the nutrients created large areas without oxygen, which caused a mass extinction of marine species, while the levels of CO 2 dropped all over the world, allowing the formation of ice caps on the poles. Moss gametophytes are autotrophic and require sunlight to perform photosynthesis . Shade tolerance varies by species, just as it does with higher plants. In most areas, mosses grow chiefly in moist, shaded areas, such as wooded areas and at
5724-430: The capsule enlarges and matures before its stalk elongates. Other differences are not universal for all mosses and all liverworts, but the presence of a clearly differentiated stem with simple-shaped, non-vascular leaves that are not arranged in three ranks, all point to the plant being a moss. Vascular plants have two sets of chromosomes in their vegetative cells and are said to be diploid , i.e. each chromosome has
5832-407: The capsule is mature. Within the capsule, spore-producing cells undergo meiosis to form haploid spores, upon which the cycle can start again. The mouth of the capsule is usually ringed by a set of teeth called peristome. This may be absent in some mosses. Most mosses rely on the wind to disperse the spores. In the genus Sphagnum the spores are projected about 10–20 cm (4–8 in) off
5940-437: The chromosome constitution. Dihaploids (which are diploid) are important for selective breeding of tetraploid crop plants (notably potatoes), because selection is faster with diploids than with tetraploids. Tetraploids can be reconstituted from the diploids, for example by somatic fusion. The term "dihaploid" was coined by Bender to combine in one word the number of genome copies (diploid) and their origin (haploid). The term
6048-453: The chromosome number is generally reduced only by the specialized process of meiosis, the somatic cells of the body inherit and maintain the chromosome number of the zygote by mitosis. However, in many situations somatic cells double their copy number by means of endoreduplication as an aspect of cellular differentiation . For example, the hearts of two-year-old human children contain 85% diploid and 15% tetraploid nuclei, but by 12 years of age
6156-449: The classes Bryopsida, Marchantiopsida, and Anthocerotopsida, respectively. The mosses and liverworts are now considered to belong to a clade called Setaphyta . The mosses, (Bryophyta sensu stricto), are divided into eight classes: vascular plants hornworts liverworts Takakiopsida Sphagnopsida Andreaeopsida Andreaeobryopsida Oedipodiopsida Polytrichopsida Tetraphidopsida Bryopsida Six of
6264-499: The condition is called triploid syndrome . In unicellular organisms the ploidy nutrient limitation hypothesis suggests that nutrient limitation should encourage haploidy in preference to higher ploidies. This hypothesis is due to the higher surface-to-volume ratio of haploids, which eases nutrient uptake, thereby increasing the internal nutrient-to-demand ratio. Mable 2001 finds Saccharomyces cerevisiae to be somewhat inconsistent with this hypothesis however, as haploid growth
6372-539: The crotch. In cool, humid, cloudy climates, all sides of tree trunks and rocks may be equally moist enough for moss growth. Each species of moss requires certain amounts of moisture and sunlight and thus will grow on certain sections of the same tree or rock. Some mosses grow underwater, or completely waterlogged. Many prefer well-drained locations. There are mosses that preferentially grow on rocks and tree trunks of various chemistries. In boreal forests , some species of moss play an important role in providing nitrogen for
6480-423: The diploid stage are under less efficient natural selection than those genes expressed in the haploid stage is referred to as the “masking theory”. Evidence in support of this masking theory has been reported in studies of the single-celled yeast Saccharomyces cerevisiae . In further support of the masking theory, evidence of strong purifying selection in haploid tissue-specific genes has been reported for
6588-413: The eastern edge of the town. The stadium is used for speedway and football. There is also a clay tennis court. The stadium is the home venue for the team PDK Mšeno . A valuable and numerous set of two-storey timbered and half-timbered small-town architecture is typical for the outskirts of the town. Most of the older buildings on the square disappeared during a large fire in 1867. The current appearance of
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#17328012815066696-405: The ecosystem due to their relationship with nitrogen-fixing cyanobacteria . Cyanobacteria colonize moss and receive shelter in return for providing fixed nitrogen. Moss releases the fixed nitrogen, along with other nutrients, into the soil "upon disturbances like drying-rewetting and fire events", making it available throughout the ecosystem. Moss is often considered a weed in grass lawns, but
6804-585: The edges of streams, but they can grow anywhere in cool, humid, cloudy climates, and some species are adapted to sunny, seasonally dry areas like alpine rocks or stabilized sand dunes. Choice of substrate varies by species as well. Moss species can be classed as growing on: rocks, exposed mineral soil, disturbed soils, acid soil, calcareous soil, cliff seeps and waterfall spray areas, streamsides, shaded humusy soil, downed logs, burnt stumps, tree trunk bases, upper tree trunks, and tree branches or in bogs . Moss species growing on or under trees are often specific about
6912-613: The eight classes contain only one or two genera each. Polytrichopsida includes 23 genera, and Bryopsida includes the majority of moss diversity with over 95% of moss species belonging to this class. The Sphagnopsida, the peat-mosses, comprise the two living genera Ambuchanania and Sphagnum , as well as fossil taxa. Sphagnum is a diverse, widespread, and economically important one. These large mosses form extensive acidic bogs in peat swamps. The leaves of Sphagnum have large dead cells alternating with living photosynthetic cells. The dead cells help to store water. Aside from this character,
7020-420: The exception of the ancient group Takakiopsida , no known mosses form mycorrhiza , but bryophilous fungi is widespread in moss and other bryophytes, where they live as saprotrophs, parasites, pathogens and mutualists, some of them endophytes . Mosses differ from vascular plants in lacking water-bearing xylem tracheids or vessels . As in liverworts and hornworts , the haploid gametophyte generation
7128-472: The female shoot where their growth is restricted to a few millimeters. In some species, dwarfness is genetically determined, in that all male spores become dwarf. More often, it is environmentally determined in that male spores that land on a female become dwarf, while those that land elsewhere develop into large, female-sized males. In the latter case, dwarf males that are transplanted from females to another substrate develop into large shoots, suggesting that
7236-468: The females emit a substance which inhibits the growth of germinating males and possibly also quickens their onset of sexual maturation. The nature of such a substance is unknown, but the phytohormone auxin may be involved Having the males growing as dwarfs on the female is expected to increase the fertilization efficiency by minimizing the distance between male and female reproductive organs. Accordingly, it has been observed that fertilization frequency
7344-443: The fertilization distance. After fertilisation, the immature sporophyte pushes its way out of the archegonial venter. It takes several months for the sporophyte to mature. The sporophyte body comprises a long stalk, called a seta, and a capsule capped by a cap called the operculum . The capsule and operculum are in turn sheathed by a haploid calyptra which is the remains of the archegonial venter. The calyptra usually falls off when
7452-401: The fins on a heat sink. These carry out photosynthesis and may help to conserve moisture by partially enclosing the gas exchange surfaces. The Polytrichopsida differ from other mosses in other details of their development and anatomy too, and can also become larger than most other mosses, with e.g., Polytrichum commune forming cushions up to 40 cm (16 in) high. The tallest land moss,
7560-425: The gametes produced by the tetraploid organism in the example above, since these gametes are numerically diploid. The term monoploid is often used as a less ambiguous way to describe a single set of chromosomes; by this second definition, haploid and monoploid are identical and can be used interchangeably. Gametes ( sperm and ova ) are haploid cells. The haploid gametes produced by most organisms combine to form
7668-636: The genus Sphagnum ), although they are also used for decorative purposes, such as in gardens and in the florist trade. Traditional uses of mosses included as insulation and for the ability to absorb liquids up to 20 times their weight. Moss is a keystone genus and benefits habitat restoration and reforestation . Botanically, mosses are non-vascular plants in the land plant division Bryophyta. They are usually small (a few centimeters tall) herbaceous (non-woody) plants that absorb water and nutrients mainly through their leaves and harvest carbon dioxide and sunlight to create food by photosynthesis . With
7776-614: The ground by compressed air contained in the capsules; the spores are accelerated to about 36,000 times the earth's gravitational acceleration g . It has recently been found that microarthropods, such as springtails and mites , can effect moss fertilization and that this process is mediated by moss-emitted scents. Male and female fire moss , for example emit different and complex volatile organic scents. Female plants emit more compounds than male plants. Springtails were found to choose female plants preferentially, and one study found that springtails enhance moss fertilization, suggesting
7884-479: The growing prosperity of the area. In 1367, Charles IV promoted Mšeno to a town. During the Thirty Years' War the town suffered, but in the 17th and 18th centuries, the town prospered and the population grew. In 1879, the railroad was built, and in 1901, the school was opened. Mšeno is located on the railway line Mělník – Mladějov . The Mšeno Speedway Stadium is a motorcycle speedway track located on
7992-419: The haploid number n = 21). The gametes are haploid for their own species, but triploid, with three sets of chromosomes, by comparison to a probable evolutionary ancestor, einkorn wheat . Tetraploidy (four sets of chromosomes, 2 n = 4 x ) is common in many plant species, and also occurs in amphibians , reptiles , and insects . For example, species of Xenopus (African toads) form
8100-532: The hybridization of two separate species. In plants, this probably most often occurs from the pairing of meiotically unreduced gametes , and not by diploid–diploid hybridization followed by chromosome doubling. The so-called Brassica triangle is an example of allopolyploidy, where three different parent species have hybridized in all possible pair combinations to produce three new species. Polyploidy occurs commonly in plants, but rarely in animals. Even in diploid organisms, many somatic cells are polyploid due to
8208-583: The idea that haploidy is selected by harsher conditions – is cast into doubt by these results. Older WGDs have also been investigated. Only as recently as 2015 was the ancient whole genome duplication in Baker's yeast proven to be allopolyploid , by Marcet-Houben and Gabaldón 2015. It still remains to be explained why there are not more polyploid events in fungi, and the place of neopolyploidy and mesopolyploidy in fungal history . The concept that those genes of an organism that are expressed exclusively in
8316-664: The leaf can be smooth or it may have teeth. There may be a distinct type of cell defining the edge of the leaf, distinct in shape and/or colour from the other leaf cells. Moss has threadlike rhizoids that anchor them to their substrate, comparable to root hairs rather than the more substantial root structures of spermatophytes . Mosses do not absorb water or nutrients from their substrate through their rhizoids. They can be distinguished from liverworts ( Marchantiophyta or Hepaticae) by their multi-cellular rhizoids. Spore-bearing capsules or sporangia of mosses are borne singly on long, unbranched stems, thereby distinguishing them from
8424-626: The local climate, mosses in green roofs require no irrigation once established and are low maintenance. Mosses are also used on green walls . Haploid Ploidy ( / ˈ p l ɔɪ d i / ) is the number of complete sets of chromosomes in a cell , and hence the number of possible alleles for autosomal and pseudoautosomal genes . Here sets of chromosomes refers to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair—the form in which chromosomes naturally exist. Somatic cells , tissues , and individual organisms can be described according to
8532-611: The main urban spaces is determined by the late Neoclassical and eclectic buildings. In 1842, the town hall was built, then it was rebuilt and raised in the neo-Gothic style in 1864. The predecessor of today's parish church was allegedly the Romanesque Church of Saint Wenceslaus. In 1876–1879, the Church of Saint Martin was built. It has a high tower and it is the main urban and landscape landmark. Moss Mosses are small, non-vascular flowerless plants in
8640-455: The monoploid number and haploid number are equal; in humans, both are equal to 23. When a human germ cell undergoes meiosis, the diploid 46 chromosome complement is split in half to form haploid gametes. After fusion of a male and a female gamete (each containing 1 set of 23 chromosomes) during fertilization , the resulting zygote again has the full complement of 46 chromosomes: 2 sets of 23 chromosomes. Euploidy and aneuploidy describe having
8748-418: The most generic sense, haploid refers to having the number of sets of chromosomes normally found in a gamete . Because two gametes necessarily combine during sexual reproduction to form a single zygote from which somatic cells are generated, healthy gametes always possess exactly half the number of sets of chromosomes found in the somatic cells, and therefore "haploid" in this sense refers to having exactly half
8856-565: The number of chromosomes may have originated in this way, this is no longer clear, and the monoploid number is regarded as the same as the haploid number. Thus in humans, x = n = 23. Diploid cells have two homologous copies of each chromosome , usually one from the mother and one from the father . All or nearly all mammals are diploid organisms. The suspected tetraploid (possessing four-chromosome sets) plains viscacha rat ( Tympanoctomys barrerae ) and golden viscacha rat ( Pipanacoctomys aureus ) have been regarded as
8964-406: The number of sets of chromosomes found in a somatic cell. By this definition, an organism whose gametic cells contain a single copy of each chromosome (one set of chromosomes) may be considered haploid while the somatic cells, containing two copies of each chromosome (two sets of chromosomes), are diploid. This scheme of diploid somatic cells and haploid gametes is widely used in the animal kingdom and
9072-544: The number of sets of chromosomes present (the "ploidy level"): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is often used to describe cells with three or more sets of chromosomes. Virtually all sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different organisms, between different tissues within
9180-694: The only known exceptions (as of 2004). However, some genetic studies have rejected any polyploidism in mammals as unlikely, and suggest that amplification and dispersion of repetitive sequences best explain the large genome size of these two rodents. All normal diploid individuals have some small fraction of cells that display polyploidy . Human diploid cells have 46 chromosomes (the somatic number, 2n ) and human haploid gametes (egg and sperm) have 23 chromosomes ( n ). Retroviruses that contain two copies of their RNA genome in each viral particle are also said to be diploid. Examples include human foamy virus , human T-lymphotropic virus , and HIV . Polyploidy
9288-409: The organism as it now reproduces. Common wheat ( Triticum aestivum ) is an organism in which x and n differ. Each plant has a total of six sets of chromosomes (with two sets likely having been obtained from each of three different diploid species that are its distant ancestors). The somatic cells are hexaploid, 2 n = 6 x = 42 (where the monoploid number x = 7 and
9396-426: The pattern in all vascular plants ( seed plants and pteridophytes ), where the diploid sporophyte generation is dominant. Lichens may superficially resemble mosses, and sometimes have common names that include the word "moss" (e.g., " reindeer moss " or " Iceland moss "), but they are fungal symbioses and not related to mosses. The main commercial significance of mosses is as the main constituent of peat (mostly
9504-480: The perichaetum (plural, perichaeta). The archegonia are small flask-shaped clumps of cells with an open neck (venter) down which the male sperm swim. The male organs are known as antheridia ( sing. antheridium ) and are enclosed by modified leaves called the perigonium ( pl. perigonia). The surrounding leaves in some mosses form a splash cup, allowing the sperm contained in the cup to be splashed to neighboring stalks by falling water droplets. Gametophore tip growth
9612-403: The plant Scots Pine . The common potato ( Solanum tuberosum ) is an example of a tetraploid organism, carrying four sets of chromosomes. During sexual reproduction, each potato plant inherits two sets of 12 chromosomes from the pollen parent, and two sets of 12 chromosomes from the ovule parent. The four sets combined provide a full complement of 48 chromosomes. The haploid number (half of 48)
9720-538: The principal sensor of DNA double-strand breaks) showed that these genes are necessary for repair of DNA damage as well as for normal growth and development. More recently, mosses have been grouped with the liverworts and hornworts in the division Bryophyta ( bryophytes , or Bryophyta sensu lato ). The bryophyte division itself contains three (former) divisions: Bryophyta (mosses), Marchantiophyta (liverworts) and Anthocerotophyta (hornworts); it has been proposed that these latter divisions are de-ranked to
9828-464: The production of a diploid sporophyte. The sperm of mosses is biflagellate, i.e. they have two flagellae that aid in propulsion. Since the sperm must swim to the archegonium, fertilisation cannot occur without water. Some species (for example Mnium hornum or several species of Polytrichum ) keep their antheridia in so called 'splash cups', bowl-like structures on the shoot tips that propel the sperm several decimeters when water droplets hit it, increasing
9936-400: The proportions become approximately equal, and adults examined contained 27% diploid, 71% tetraploid and 2% octaploid nuclei. There is continued study and debate regarding the fitness advantages or disadvantages conferred by different ploidy levels. A study comparing the karyotypes of endangered or invasive plants with those of their relatives found that being polyploid as opposed to diploid
10044-418: The remaining classes, stomata have been lost more than 60 times. Their leaves are simple, usually only a single layer of cells with no internal air spaces, often with thicker midribs (nerves). The nerve can run beyond the edge of the leaf tip, termed excurrent. The tip of the leaf blade can be extended as a hair point, made of colourless cells. These appear white against the dark green of the leaves. The edge of
10152-570: The repair mechanism functions in plants. For example, a study of P. patens mutants defective in Rp RAD51, a gene that encodes a protein at the core of the recombinational repair reaction, indicated that homologous recombination is essential for repairing DNA double-strand breaks in this plant. Similarly, studies of mutants defective in Ppmre11 or Pprad50 (that encode key proteins of the MRN complex ,
10260-568: The repair mechanism known as homologous recombination . If the plant cannot repair DNA damage, e.g., double-strand breaks , in their somatic cells , the cells can lose normal functions or die. If this occurs during meiosis (part of sexual reproduction), they could become infertile. The genome of P. patens has been sequenced, which has allowed several genes involved in DNA repair to be identified. P. patens mutants that are defective in key steps of homologous recombination have been used to work out how
10368-684: The rest of the body being diploid (as in the mammalian liver ). For many organisms, especially plants and fungi, changes in ploidy level between generations are major drivers of speciation . In mammals and birds, ploidy changes are typically fatal. There is, however, evidence of polyploidy in organisms now considered to be diploid, suggesting that polyploidy has contributed to evolutionary diversification in plants and animals through successive rounds of polyploidization and rediploidization. Humans are diploid organisms, normally carrying two complete sets of chromosomes in their somatic cells: one copy of paternal and maternal chromosomes, respectively, in each of
10476-442: The rocks they were growing on. These chemically altered rocks in turn reacted with the atmospheric CO 2 and formed new carbonate rocks in the ocean through the weathering of calcium and magnesium ions from silicate rocks. The weathered rocks also released significant amounts of phosphorus and iron which ended up in the oceans, where it caused massive algal blooms, resulting in organic carbon burial, extracting more carbon dioxide from
10584-450: The same organism . Though polyploidy in humans is not viable, mixoploidy has been found in live adults and children. There are two types: diploid-triploid mixoploidy, in which some cells have 46 chromosomes and some have 69, and diploid-tetraploid mixoploidy, in which some cells have 46 and some have 92 chromosomes. It is a major topic of cytology. Dihaploid and polyhaploid cells are formed by haploidisation of polyploids, i.e., by halving
10692-462: The same organism, and at different stages in an organism's life cycle. Half of all known plant genera contain polyploid species, and about two-thirds of all grasses are polyploid. Many animals are uniformly diploid, though polyploidy is common in invertebrates, reptiles, and amphibians. In some species, ploidy varies between individuals of the same species (as in the social insects ), and in others entire tissues and organ systems may be polyploid despite
10800-500: The same species or at different stages of the life cycle . In some insects it differs by caste . In humans, only the gametes are haploid, but in many of the social insects , including ants , bees , and termites , males develop from unfertilized eggs, making them haploid for their entire lives, even as adults. In the Australian bulldog ant, Myrmecia pilosula , a haplodiploid species, haploid individuals of this species have
10908-473: The species of trees they grow on, such as preferring conifers over broadleaf trees , oaks over alders , or vice versa. While mosses often grow on trees as epiphytes , they are never parasitic on the tree. Mosses are also found in cracks between paving stones in damp city streets, and on roofs. Some species adapted to disturbed, sunny areas are well adapted to urban conditions and are commonly found in cities. Examples would be Rhytidiadelphus squarrosus ,
11016-547: The suffix -somy (rather than -ploidy , used for euploid karyotypes), such as trisomy and monosomy . Homoploid means "at the same ploidy level", i.e. having the same number of homologous chromosomes . For example, homoploid hybridization is hybridization where the offspring have the same ploidy level as the two parental species. This contrasts with a common situation in plants where chromosome doubling accompanies or occurs soon after hybridization. Similarly, homoploid speciation contrasts with polyploid speciation . Zygoidy
11124-433: The tallest moss in the world, can grow to 50 cm (20 in) in height. There are approximately 12,000 species. Mosses are commonly confused with liverworts, hornworts and lichens . Although often described as non-vascular plants , many mosses have advanced vascular systems. Like liverworts and hornworts, the haploid gametophyte generation of mosses is the dominant phase of the life cycle . This contrasts with
11232-486: The taxonomic division Bryophyta ( / b r aɪ ˈ ɒ f ə t ə / , / ˌ b r aɪ . ə ˈ f aɪ t ə / ) sensu stricto . Bryophyta ( sensu lato , Schimp . 1879 ) may also refer to the parent group bryophytes , which comprise liverworts , mosses, and hornworts . Mosses typically form dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to
11340-491: The terms haploid and diploid in 1905. Some authors suggest that Strasburger based the terms on August Weismann 's conception of the id (or germ plasm ), hence haplo- id and diplo- id . The two terms were brought into the English language from German through William Henry Lang 's 1908 translation of a 1906 textbook by Strasburger and colleagues. The term haploid is used with two distinct but related definitions. In
11448-496: The unique branching, thallose (flat and expanded) protonema, and explosively rupturing sporangium place it apart from other mosses. Andreaeopsida and Andreaeobryopsida are distinguished by the biseriate (two rows of cells) rhizoids, multiseriate (many rows of cells) protonema, and sporangium that splits along longitudinal lines. Most mosses have capsules that open at the top. Polytrichopsida have leaves with sets of parallel lamellae, flaps of chloroplast-containing cells that look like
11556-458: The wild in a water-retaining bag. Some species of moss can be extremely difficult to maintain away from their natural sites with their unique requirements of combinations of light, humidity, substrate chemistry, shelter from wind, etc. Growing moss from spores is even less controlled. Moss spores fall in a constant rain on exposed surfaces; those surfaces which are hospitable to a certain species of moss will typically be colonised by that moss within
11664-513: The year to complete fertilisation. Many mosses can survive desiccation , sometimes for months, returning to life within a few hours of rehydration. It is generally believed that in the Northern Hemisphere , the north side of trees and rocks will generally have more luxuriant moss growth on average than other sides. The reason is assumed to be because sunshine on the south side causes a dry environment. The reverse would be true in
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