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Dioicy (botany)
Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis rather than meiosis, so that sperm and eggs are genetically identical with their parent gametophyte. Description Dioicy promotes outcrossing. Sexual dimorphism is commonly found in dioicous species. However, according to Bernard Goffinet sexual dimorphism is rare in dioicous moss species. Dioicy is correlated with reduced sporophyte production, due to spatial separation of male and female colonies, scarcity or absence of males. The term dioecy is meaningless for bryophytes because it refers to the sexuality of sporophytes. Nonetheless dioecy and dioicy are comparable in many respects. Etymology The words dioicous and di(o)ecious are derived from οἶκος or οἰκία and δι- (di-), twice, double. (''(o)e'' is the Latin way ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual System
A sexual system is a pattern of sex allocation or a distribution of male and female function across organisms in a species. Terms like reproductive system and mating system have also been used as synonyms. The distinction between sexual systems is not always clear due to phenotypic plasticity. Sexual systems are viewed as a key factor for genetic variation and reproductive success, and may have also led to the origin or extinction of certain species. Interests in sexual systems go back to Charles Darwin, Darwin, who found that barnacles contain species that are Androdioecy, androdioecious and some that are Dioecy, dioecious. Types of sexual systems In plants there are monomorphic sexual systems where a species has hermaphrodite, male and/or female flowers on the same plant. Monomorphic sexual systems include Monoecious (botany), monoecy, gynomonoecy, andromonoecy and trimonoecy. There are also dimorphic sexual systems like dioecy, gynodioecy and androdioecy. Mixed sexual syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bryophytes
The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments. The bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they do not produce flowers or seeds. They reproduce sexually by spores and asexually by fragmentation or the production of gemmae. 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 . Terminology The term "Bryophyta" was first suggested by Braun in 1864. G.M. Smith placed this group between Algae and Pteridophyta. Features The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Specialization
Sex is the biological distinction of an organism between male and female. Sex or SEX may also refer to: Biology and behaviour *Animal sexual behaviour **Copulation (zoology) **Human sexual activity **Non-penetrative sex, or sexual outercourse **Sex drive, a person's overall sexual drive or desire for sexual activity **Sexual intercourse, also called copulation or coitus *Gender, the distinction between male and female or masculinity and femininity within an individual's gender identity **Sex and gender distinction *Human sexuality *Mating types, a distinction of gametes, whether in anisogamous or isogamous species * Sexing, the act of discerning the sex of an animal *Sexual reproduction, a process of combining and mixing genetic traits, associated with the generation of new individuals, by means of meiosis and fertilization **Genetic recombination, the process of mixing genetic traits solely, occurring both in organisms with sexual or asexual reproduction Art and entertainment Fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hornwort
Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information; the flattened, green plant body of a hornwort is the gametophyte stage of the plant. Hornworts may be found worldwide, though they tend to grow only in places that are damp or humid. Some species grow in large numbers as tiny weeds in the soil of gardens and cultivated fields. Large tropical and sub-tropical species of ''Dendroceros'' may be found growing on the bark of trees. The total number of species is still uncertain. While there are more than 300 published species names, the actual number could be as low as 100-150 species. Description Like all bryophytes, the dominant life phase of a hornwort is the haploid gametophyte. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plesiomorphy And Symplesiomorphy
In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and synapomorphy, all mean a trait shared between species because they share an ancestral species. Apomorphic and synapomorphic characteristics convey much information about evolutionary clades and can be used to define taxa. However, plesiomorphic and symplesiomorphic characteristics cannot. The term ''symplesiomorphy'' was introduced in 1950 by German entomologist Willi Hennig. Examples A backbone is a plesiomorphic trait shared by birds and mammals, and does not help in placing an animal in one or the other of these two clades. Birds and mammals share this trait because both clades are descended from the same far distant ancestor. Other clades, e.g. snakes, lizards, turtles, fish, frogs, all have backbones and none are either birds nor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monoicous
Monoicy () is a sexual system in haploid plants (mainly bryophytes) where both sperm and eggs are produced on the same gametophyte, in contrast with dioicy, where each gametophyte produces only sperm or eggs but never both.Crandall-Stotler, B.J. & Bartholomew-Began, S.E. (2007). ''Morphology of Mosses (Phylum Bryophyta)''. In: Flora of North America Editorial Committee, eds. (1993+). ''Flora of North America North of Mexico''. 16+ vols. New York and Oxford. Volume 27, 2007.Bell, P.R. & Helmsley, A.R. (2000). ''Green plants, their origin and diversity'' (2nd ed.). Cambridge University Press. Both monoicous () and dioicous gametophytes produce gametes in gametangia by mitosis rather than meiosis, so that sperm and eggs are genetically identical with their parent gametophyte. It has been suggested that monoicy may have benefits in dry habitats where the ability to produce sporophytes is limited due to lack of water. Monoicy is similar to, and often conflated with, monoecy, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex-determination System
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes. In some species there are hermaphrodites. There are also some species that are only one sex due to parthenogenesis, the act of a female reproducing without fertilization. In some species, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology. In animals this is often accompanied by chromosomal differences, generally through combinations of XY, ZW, XO, ZO chromosomes, or haplodiploidy. The sexual differentiation is generally triggered by a main gene (a "sex locus"), with a multitude of other genes following in a domino effect. In other cases, sex of a fetus is determined by environmental variables (such as temperature). The details of some sex-determination systems are not yet fully underst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Algae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and polar regions. They are dominant on rocky shores throughout cooler areas of the world. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, ''Macrocystis'', a kelp of the order Laminariales, may reach in length and forms prominent underwater kelp forests. Kelp forests like these contain a high level of biodiversity. Another example is ''Sargassum'', which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Some members of the class, such as kelps, are used by humans as food. Between 1,500 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coleochaetales
Coleochaetaceae is a family of algae. It is the only family in the Coleochaetales, an order of parenchymous charophyte algae, that includes some of the closest multicellular relatives of land plants. They questionably include the fossil genus ''Parka A parka or anorak is a type of coat with a hood, often lined with fur or faux fur. This kind of garment is a staple of Inuit clothing, traditionally made from caribou or seal skin, for hunting and kayaking in the frigid Arctic. Some Inuit ano ...''. References Charophyta Green algae orders {{alga-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charales
Charales is an order of freshwater green algae in the division Charophyta, class Charophyceae, commonly known as stoneworts. Depending on the treatment of the genus ''Nitellopsis'', living (extant) species are placed into either one family ( Characeae) or two (Characeae and Feistiellaceae). Further families are used for fossil members of the order. Linnaeus established the genus '' Chara'' in 1753. Taxonomy The higher level classification of green algae was unsettled . AlgaeBase places Charales within the class Charophyceae and its circumscription of the division Charophyta. Families The number of families and their division into genera varies. , AlgaeBase accepts two families containing some extant species and four families containing only fossil species: * Characeae S.F.Gray * Feistiellaceae Schudack *† Aclistocharaceae X.G.Zhou (may be included in Characeae) *† Atopocharaceae R.E.Peck (may be included in Clavatoraceae) *† Clavatoraceae Pia *† Porocharaceae Grambas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hornwort
Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information; the flattened, green plant body of a hornwort is the gametophyte stage of the plant. Hornworts may be found worldwide, though they tend to grow only in places that are damp or humid. Some species grow in large numbers as tiny weeds in the soil of gardens and cultivated fields. Large tropical and sub-tropical species of ''Dendroceros'' may be found growing on the bark of trees. The total number of species is still uncertain. While there are more than 300 published species names, the actual number could be as low as 100-150 species. Description Like all bryophytes, the dominant life phase of a hornwort is the haploid gametophyte. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' 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 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 tall, though some species are much larger. ''Dawsonia'', the tallest moss in the world, can grow to in height. There are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
