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Hermaphroditic
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. For example, the great majority of tunicates, pulmonate molluscs, opisthobranch, earthworms, and slugs are hermaphrodites. Hermaphroditism is also found in some fish species and to a lesser degree in other vertebrates. Most plants are also hermaphrodites. Animal species having different sexes, male and female, are called gonochoric, which is the opposite of hermaphrodite. There are also species where hermaphrodites exist alongside males (called androdioecy) or alongside females (called gynodioecy), or all three exist in the same species (called trioecy); these three system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gynodioecy
Gynodioecy is a rare breeding system that is found in certain flowering plant species in which female and hermaphroditic plants coexist within a population. Gynodioecy is the evolutionary intermediate between hermaphroditism (exhibiting both female and male parts) and dioecy (having two distinct morphs: male and female). Gynodioecy is sometimes considered a mixed breeding system alongside trioecy and androdioecy. It is also considered a dimorphic sexual system alongside dioecy and androdioecy. Gynodioecy occurs as a result of a genetic mutation that inhibits a hermaphroditic plant from producing pollen, while keeping the female reproductive parts intact. Gynodioecy is extremely rare, with fewer than 1% of angiosperm species exhibiting the breeding system. Some notable taxa that exhibit a gynodioecious mating system include ''Beta vulgaris'' (wild beet), '' Lobelia siphilitica'', '' Silene'', and Lamiaceae. Evolution Gynodioecy is often referred to as the evolutionary int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexes
Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones ( ova, often called egg cells). Organisms that produce both types of gametes are called hermaphrodites. During sexual reproduction, male and female gametes fuse to form zygotes, which develop into offspring that inherit traits from each parent. Males and females of a species may have physical similarities (sexual monomorphism) or differences (sexual dimorphism) that reflect various reproductive pressures on the respective sexes. Mate choice and sexual selection can accelerate the evolution of physical differences between the sexes. The terms ''male'' and ''female'' typically do not apply in sexually undifferentiated species in which the individuals are isomorphic (look the same) and the gametes are isogamous (indistinguishable in size and shape ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gonochorism
In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism contrasts with simultaneous hermaphroditism but it may be hard to tell if a species is gonochoric or sequentially hermaphroditic. (e.g. Parrotfish, '' Patella ferruginea''). However, in gonochoric species individuals remain either male or female throughout their lives. Species that reproduce by thelytokous parthenogenesis and do not have males can still be classified as gonochoric. Terminology The term is derived from Greek (''gone'', generation) + (''chorizein,'' to separate). The term gonochorism originally came from German gonochorismus. Gonochorism is also referred to as unisexualism or gonochory. Evolution Gonochorism has evolved independently multiple times and is very evolutionary stable in animals. Its stability and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Androdioecy
Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has been considered a stepping stone in the transition from dioecy to hermaphroditism, and vice versa. Androdioecy is sometimes referred to as a mixed breeding system with trioecy and gynodioecy. It is a dimorphic sexual system in plants alongside gynodioecy and dioecy. Evolution of androdioecy The fitness requirements for androdioecy to arise and sustain itself are theoretically so improbable that it was long considered that such systems do not exist. Particularly, males and hermaphrodites have to have the same fitness, in other words the same number of offspring, in order to be maintained. However, males only have offspring by fertilizing eggs or ovules of hermaphrodites, while hermaphrodites have offspring both through fertilizing eggs o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioecy
Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is biparental reproduction. Dioecy has costs, since only about half the population directly produces offspring. It is one method for excluding self-fertilization and promoting allogamy (outcrossing), and thus tends to reduce the expression of recessive deleterious mutations present in a population. Plants have several other methods of preventing self-fertilization including, for example, dichogamy, herkogamy, and self-incompatibility. Dioecy is a dimorphic sexual system, alongside gynodioecy and androdioecy. In zoology In zoology, dioecious species may be opposed to hermaphroditic species, meaning that an individual is either male or female, in which case the synonym gonochory is more often used. Most animal species are dioeci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes ( diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes. Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. Sexual reproduction also occurs in some unicellular eukaryotes. Sexual reproduction does not occur in prokaryotes, unicellular organisms without cell nuclei, such bacteria and archaea. However, some process in bacteria may be considered analogous to sexual reproduction in that they incorporate new genetic information, including bacterial conjugation, transforma ... [...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 Darwin, who found that barnacles contain species that are androdioecious and some that are 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 monoecy, gynomonoecy, andromonoecy and trimonoecy. There are also dimorphic sexual systems like dioecy, gynodioecy and androdioecy. Mixed sexual systems are where hermaphrodites coexist with s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulmonate
Pulmonata or pulmonates, is an informal group (previously an Order (biology), order, and before that a Class (biology), subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a Respiratory system of gastropods#Pulmonates, pallial lung instead of a gill, or gills. The group includes many land and freshwater families, and several marine families. The taxon Pulmonata as traditionally defined was found to be polyphyletic in a molecular study per Jörger ''et al.'', dating from 2010. Pulmonata are known from the Carboniferous Period to the present. Pulmonates have a single Atrium (heart), atrium and kidney, and a concentrated, symmetrical, nervous system. The mantle cavity is located on the right side of the body, and lacks gills, instead being converted into a blood vessel, vascularised lung. Most species have a shell, but no operculum (gastropod), operculum, although the group does also include several shell-less slugs. Pulmonates are hermap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates comprise such groups as the following: * jawless fish, which include hagfish and lampreys * jawed vertebrates, which include: ** cartilaginous fish (sharks, rays, and ratfish) ** bony vertebrates, which include: *** ray-fins (the majority of living bony fish) *** lobe-fins, which include: **** coelacanths and lungfish **** tetrapods (limbed vertebrates) Extant vertebrates range in size from the frog species ''Paedophryne amauensis'', at as little as , to the blue whale, at up to . Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andromonoecious
Andromonoecy is a breeding system of plant species in which male and hermaphrodite flowers are on the same plant. It is a monomorphic sexual system alongside monoecy, gynomonoecy and trimonoecy. Andromonoecy is frequent among genera with zygomorphic flowers, however it is overall rare and occurs in less than 2% of plant species. Nonetheless the breeding system has gained interest among biologists in the study of sex expression. Etymology The word andromonoecious is a combination of andr- (meaning male) and monoecious and was first used in 1877. Prevalence It is uncommon and has been estimated to occur in less than 2% of plant species. In angiosperms, it occurs in 1.7% of angiosperms making up around 4000 species in 33 families. It is common in the grass subfamily Panicoideae. Andromonoecious species * ''Cucumis melo'' subsp * '' Cucumis melo'' * '' Chaerophyllum bulbosum'' * '' Erophaca baetica'' * '' Silene tibetica'' '' Solanum'' * '' Solanum agnewiorum'' * '' S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trioecy
Trioecy, or subdioecy, is a rare sexual system characterized by the coexistence of males, females, and hermaphrodites. It has been found in both plants and animals. Trioecy is sometimes referred to as a mixed mating system alongside androdioecy and gynodioecy. Evolution of trioecy Many speculate trioecy is a transient state and is often associated with evolutionary transitioning from gynodioecy to dioecy. Other studies show that trioecious populations originated from gonochoristic ancestors which were invaded by a mutant selfing hermaphrodite, creating a trioecious population. It has been suggested that chromosomal duplication is an important part in the evolution of trioecy. Evolutionary stability Trioecy is usually viewed as evolutionarily unstable, but its exact stability is unclear. Like in brachiopod species trioecy usually breaks into androdioecy or gynodioecy. But one study found that trioecy can be stable under nucleocytoplasmic sex determination. Another theoretica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snails Mating
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called ''slugs'', and land snails that have only a very small shell (that they cannot retract into) are often called '' semi-slugs''. Snails have considerable human relevance, including as food items, as pests, and as vectors of disease, and their shells are used as decorative objects and are incorporated into jewelry. The snail has also had some cultural significance, tending to be associated with lethargy. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
