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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 mating system comparable with trioecy and androdioecy. It is also considered a dimorphic sexual system alongside dioecy and androdioecy. Gynodioecy occurs as a result of transmission of nuclear (nuclear male sterility) or, more commonly, extra-nuclear (e.g. cytoplasmic male sterility) mutated alleles, which prevents pollen production, while keeping the female reproductive parts intact; other members of the species population don't inherit the mutated alleles, thus remaining hermaphrodites. In some cases, a combination of both nuclear and extra-nuclear mechanisms is observed in determining the sterile phenotype ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex Determination In Silene
''Silene'' is a flowering plant genus that has evolved a dioecious reproductive system. This is made possible through heteromorphic sex chromosomes expressed as XY. ''Silene'' recently evolved sex chromosomes 5-10 million years ago and are widely used by geneticists and biologists to study the mechanisms of sex determination since they are one of only 39 species across 14 families of angiosperm that possess sex-determining genes. ''Silene'' are studied because of their ability to produce offspring with a plethora of reproductive systems. The common inference drawn from such studies is that the sex of the offspring is determined by the Y chromosome. Evolution of sex chromosomes Biologists have found that sex chromosomes in plants originated from pairs of autosomes. As these chromosomes diverge from their autosomal ancestor and from each other as a homologous pair, they have the potential to increase or decrease in size due to mutation and recombination. In the case of ''Silen ... [...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, trioecy and gynodioecy are sometimes referred to as a mixed mating systems. Androdioecy is a dimorphic sexual system in plants comparable with 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 produce 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 th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioecy
Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is biparental reproduction. Dioecy has costs, since only the female part of 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. In zoology In zoology, dioecy means that an animal is either male or female, in which case the synonym gonochory is more often used. Most animal species are gonochoric, almost all vertebrate species are gonochoric, and all bird and mammal species are gonochoric. Dioecy may also describe colonies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trioecy
Trioecy , also spelled triecy, is a sexual system characterized by the coexistence of males, females, and hermaphrodites. It has been found in both plants and animals. Like androdioecy and gynodioecy, trioecy is a mixed mating systems. Terminology Trioecy is also called tridioecy and subdioecy . The term trioecy comes from the Neo-Latin word '' Trioecia'', a former order of trioecious plants. Evolution of trioecy Trioecy may be an unstable transient state associated with evolutionary transitioning from gynodioecy to dioecy. In brachiopod species, trioecy usually breaks into androdioecy or gynodioecy. 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 plays an important part in the evolution of trioecy. But one study found that trioecy can be stable under nucleocytoplasmic sex determination. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual System
A sexual system is a distribution of male and female functions across organisms in a species. The terms reproductive system and mating system have also been used as synonyms. Sexual systems play a key role in genetic variation and reproductive success, and may also have led to the origin or extinction of certain species. In flowering plants and animals, sexual reproduction involves meiosis, an adaptive process for repairing damage in the germline DNA transmitted to progeny. The distinctions between different sexual systems is not always clear due to phenotypic plasticity. Interest in sexual systems goes back to Charles Darwin, who found that barnacles include some species that are androdioecious and some that are dioecious. Types of sexual systems Flowering plants may have dimorphic or monomorphic sexual systems. In monomorphic sexual systems, a combination of hermaphrodite, male, and/or female flowers may be present on the same plant. Monomorphic sexual systems inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytoplasmic Male Sterility
Cytoplasmic male sterility is total or partial male sterility in hermaphrodite organisms, as the result of specific nuclear and mitochondrial interactions. Male sterility is the failure to produce functional anthers, pollen, or male gametes. Such male sterility in hermaphrodite populations leads to gynodioecious populations (populations with coexisting fully functioning hermaphrodites and male-sterile hermaphrodites). Cytoplasmic male sterility, as the name indicates, is under extranuclear genetic control (under control of the mitochondrial or plastid genomes). It shows non-Mendelian inheritance, with male sterility inherited maternally. In general, there are two types of cytoplasm: N (normal) and aberrant S (sterile) cytoplasms. These types exhibit reciprocal differences. History Joseph Gottlieb Kölreuter was the first to document male sterility in plants. In the 18th century, he reported on anther abortion within species and specific hybrids. Cytoplasmic male sterility (CMS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schiedea Adamantis
''Schiedea adamantis'', commonly known as Diamond Head schiedea, is a species of flowering plant in the family Caryophyllaceae, that is endemic to the island of Oahu in Hawaii. It inhabits low shrublands on steep slopes along the northwest rim of Diamond Head Crater. Associated plants include nehe ( ''Lipochaeta lobata'' var. ''lobata''), kāwelu (''Eragrostis variabilis''), akoko ('' Euphorbia degeneri''), and ilima (''Sida fallax''). There are only about 30 individuals remaining, and they are threatened by habitat loss. Schiedea adamantis is a rare Hawaiian plant that is endangered due to climate change and habitat loss. It's also known as the flower of love because it's said to bring good luck in love affairs. This plant has deep green leaves that are covered with silvery scales, and bright pink flowers that bloom in the spring. It can be found growing on the slopes of Haleakala National Park on Maui, and is a favorite of horticulturalists and gardeners worldwide. This exqu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermaphrodite
A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants. A rough estimate of the number of hermaphroditic animal species ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermaphroditism
A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants. A rough estimate of the number of hermaphroditic animal species is 6 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silene
''Silene'' is a genus of flowering plants in the family Caryophyllaceae. Containing nearly 900 species, it is the largest genus in the family. Common names include campion and catchfly. Many ''Silene'' species are widely distributed, particularly in the northern hemisphere. Scientific history Members of this genus have been the subject of research by preeminent plant ecologists, evolutionary biologists, and geneticists, including Charles Darwin, Gregor Mendel, Carl Correns, Herbert G. Baker, and Janis Antonovics. Many ''Silene'' species continue to be widely used to study systems, particularly in the fields of ecology and evolutionary biology.Bernasconi et al. 2009. Silene as a model system in ecology and evolution. Heredity. 103:5-14. PMI19367316/ref> The genus has been used as a model for understanding the genetics of sex determination for over a century. ''Silene'' species commonly contain a mixture of hermaphroditic and female (or male-sterile) individuals ( gynodioecy), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining), cause an error during other forms of repair, or cause an error during replication ( translesion synthesis). Mutations may also result from substitution, insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce detectable changes in the observable characteristics ( phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity. Mutati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuchsia Excorticata
''Fuchsia excorticata'', commonly known as tree fuchsia, New Zealand fuchsia and by its Māori name , is a New Zealand native tree belonging to the family Onagraceae. It is commonly found throughout New Zealand and as far south as the Auckland Islands. It grows from sea level up to about , particularly alongside creeks and rivers. It is easily recognised in its native environment by the characteristic appearance of its bark, which peels spontaneously, hanging in red papery strips to show a pale bark underneath. Its scientific name, ''excorticata'', reflects this distinctive property. ''Fuchsia excorticata'' is the largest member of the genus ''Fuchsia'', growing to a height of . It is unusual among New Zealand trees in being deciduous in the southern parts of its range. The introduction of the common brushtail possum to New Zealand precipitated a serious decline in this species, particularly where large concentrations of the possum are present. ''F. excorticata'' appears to be o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
