Agamogenesis is any form of reproduction that does not involve a male gamete. Examples are parthenogenesis and apomixis.
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Each of these processes becomes a male gamete termed a microgamete which is equivalent to a mammalian spermatozoon.
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Immunocontraception targeting the female gamete has focused on the zona pellucida. Immunocontraception targeting the male gamete has involved many different antigens associated with sperm function.
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Fertilization and implantation in humans Through an interplay of hormones that includes follicle stimulating hormone that stimulates folliculogenesis and oogenesis creates a mature egg cell, the female gamete. Fertilization is the event where the egg cell fuses with the male gamete, spermatozoon. After the point of fertilization, the fused product of the female and male gamete is referred to as a zygote or fertilized egg. The fusion of female and male gametes usually occurs following the act of sexual intercourse.
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Spermatozoon is the male gamete. After ejaculation this cell is not mature, so it can not fertilize the oocyte. To have the ability to fertilize the female gamete, this cell suffers capacitation and acrosome reaction in female reproductive tract. The signaling pathways best described for spermatozoon involve these processes.
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Allogamy, which is also known as cross-fertilisation, refers to the fertilisation of an egg cell from one individual with the male gamete of another. Autogamy which is also known as self-fertilisation, occurs in such hermaphroditic organisms as plants and flatworms; therein, two gametes from one individual fuse.
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Pollen tubes act as conduits to transport the male gamete cells from the pollen grain—either from the stigma (in flowering plants) to the ovules at the base of the pistil or directly through ovule tissue in some gymnosperms. Pollen grains have separate structures such as microsporocytes and megasporocytes.
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Gametes carry half the genetic information of an individual, one ploidy of each type, and are created through meiosis. Oogenesis is the process of female gamete formation in animals. This process involves meiosis (including meiotic recombination) occurring in the diploid primary oocyte to produce the haploid ovum. Spermatogenesis is the process of male gamete formation in animals.
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Mars (god of war) is often used to represent the male sex. It also stands for the planet Mars and is the alchemical symbol for iron. A male (♂) organism is the physiological sex that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization.
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Problems in male meiosis resulting in a male gamete with 2 X-chromosomes. Problems in female meiosis resulting in a female gamete with 2 X-chromosomes. Triple X syndrome is not inherited, but usually occurs as an event during the formation of reproductive cells (ovum and sperm). An error in cell division called nondisjunction can result in reproductive cells with additional chromosomes.
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The Fucales include some of the more common littoral seaweeds and the members of the order have the typical seaweed construction: a holdfast, stipe, and lamina. The lamina is often much branched and may include gas-filled bladders. Growth is by division of the apical cells. They are oogamous - fusion between the small male gamete and the large female gamete.
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All sexually reproducing life, including both plants and animals, produces gametes. The male gamete cell, sperm, is usually motile whereas the female gamete cell, the ovum, is generally larger and sessile. The male and female gametes combine to produce the zygote cell. In multicellular organisms the zygote subsequently divides in an organised manner into smaller more specialised cells, so that this new individual develops into an embryo.
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Phytophthora sojae overwinters in plant debris and soil as oospores. Oospores are made after the male gamete, antheridium, and female gamete, oogonium, undergo fertilization and then sexual recombination (meiosis). They possess thick cell walls with cellulose that enables them to survive harsh conditions in the soil without germinating for several years. They begin to germinate once the environmental condition is favorable during spring (see § Environment) and produce sporangia.
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A similar imprinting phenomenon has also been described in flowering plants (angiosperms). During fertilization of the egg cell, a second, separate fertilization event gives rise to the endosperm, an extraembryonic structure that nourishes the embryo in a manner analogous to the mammalian placenta. Unlike the embryo, the endosperm is often formed from the fusion of two maternal cells with a male gamete. This results in a triploid genome.
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Vigorous and growing rapidly in woods, scrub, hillsides, and hedgerows, blackberry shrubs tolerate poor soils, readily colonizing wasteland, ditches, and vacant lots. The flowers are produced in late spring and early summer on short racemes on the tips of the flowering laterals. Each flower is about 2–3 cm in diameter with five white or pale pink petals. The drupelets only develop around ovules that are fertilized by the male gamete from a pollen grain.
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Due to the presence of pheromones as well as the dispersal of male gametes, two or more female gametes may be attracted to one conidium, or male gamete. The presence of karyogamy further supports the possibility of female-female competition. Within N. crassa, the haploid mycelium undergoes growth as vegetative tissue prior to entering the mating cycle. This vegetative tissue can be used as a source of fertilization and can fuse with the trichogyne.
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Any gene that can manipulate the odds of ending up in the egg rather than the polar body will have a transmission advantage, and will increase in frequency in a population. Segregation distortion can happen in several ways. When this process occurs during meiosis it is referred to as meiotic drive. Many forms of segregation distortion occur in male gamete formation, where there is differential mortality of spermatids during the process of sperm maturation or spermiogenesis.
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SEM image of pollen tubes growing from Lily pollen grains.A pollen tube is a tubular structure produced by the male gametophyte of seed plants when it germinates. Pollen tube elongation is an integral stage in the plant life cycle. The pollen tube acts as a conduit to transport the male gamete cells from the pollen grain—either from the stigma (in flowering plants) to the ovules at the base of the pistil or directly through ovule tissue in some gymnosperms.
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The larger immobile gametes act as female gametes, while the smaller, motile gametes act as male gametes. Increased difference in the operational sex ratio (OSR) due to asymmetry between the sex roles leads to the production of more male gametes. In addition, variation within gamete quality which could affect offspring viability or fitness can also lead to differences in female/male gamete ratios.Beekman M, Nieuwenhuis B, Ortiz-Barrientos D, Evans JP. Sexual selection in hermaphrodites, sperm and broadcast spawners, plants and fungi.
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Mushroom-forming fungi within Basidiomycetes produce sexually by the reciprocal migration of nuclei and have a male-biased OSR which aids in supporting that sexual selection is present within fungi. Although there are no traditional males present, there is variation between the mating types responsible for acting as the male or female sex role. Receiving mycelia act as the female gametes while the donating nucleus acts as the male gamete. Sexual selection might occur through male-male competition or by female choice.
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Post-copulatory mechanisms may also be present within fungi through polyandry in which zygote-level sexual selection might occur. Within multicellular ascomycete fungi, a haploid mycelium produces a fruiting body which in turn produces many offspring that are also haploid. Each fruiting body has the potential to be fertilized by more than one male gamete. Laboratory experiments have shown that multiple matings are possible and the female has the ability to selectively abort fruiting bodies that have been inappropriately fertilized by a closely related yet incompatible species.
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Triporate pollen of Oenothera speciosa Pollen of Lilium auratum showing single sulcus (monosulcate) Arabis pollen has three colpi and prominent surface structure. Pollen microspores of Lycopersicon esculentum at coenocytic tetrad stage of development observed through oil immersion microscope; the chromosomes of what will become four pollen grains can be seen. Apple pollen under microscopy Pollen itself is not the male gamete. Each pollen grain contains vegetative (non-reproductive) cells (only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell.
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Human egg cell The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, "female" gamete and a smaller, "male" one). The term is used when the female gamete is not capable of movement (non-motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. When egg and sperm fuse during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism.
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Sexual selection in fungi aids in explaining certain characteristics including the high redundancy of pheromones in the B mating-type locus as well as strong pheromone signaling in yeasts. Male gametes have the ability to reproduce asexually as asexual spores if they fail to reproduce sexually. Some fungal species are capable of producing male gametes of two different sizes. Throughout evolution, the smaller gametes have lost the ability to produce asexually in order to increase the likelihood of fertilizing a female gamete by decreasing size and increasing both the amount and motility of the male gamete.
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Main articles: Development of the human body, Human fertilization In human fertilization, a released ovum (a haploid secondary oocyte with replicate chromosome copies) and a haploid sperm cell (male gamete)—combine to form a single 2n diploid cell called the zygote. Once the single sperm enters the oocyte, it completes the division of the second meiosis forming a haploid daughter with only 23 chromosomes, almost all of the cytoplasm, and the sperm in its own pronucleus. The other product of meiosis is the second polar body with only chromosomes but no ability to replicate or survive. In the fertilized daughter, DNA is then replicated in the two separate pronuclei derived from the sperm and ovum, making the zygote's chromosome number temporarily 4n diploid.
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A gamete (; from Ancient Greek γαμετή gamete from gamein "to marry") is a haploid cell that fuses with another haploid cell during fertilization in organisms that sexually reproduce. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum— and a male produces the smaller tadpole-like type—called a sperm. In short a gamete is an egg cell (female gamete) or a sperm (male gamete). This is an example of anisogamy or heterogamy, the condition in which females and males produce gametes of different sizes (this is the case in humans; the human ovum has approximately 100,000 times the volume of a single human sperm cellMarshall, A. M. 1893.
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According to Williamson, these successful hybridisations would most likely occur in organisms with external fertilisation or male gamete dispersal. He acknowledges in his work Larvae and Evolution to have borrowed the idea of hybridogenesis from the well-known process of interspecific hybridisation that take place in plants. Hybrid plants generated from phylogenetically distant species can often give rise to new species if the hybrids become reproductively isolated from the progenitor populations. In one of his articles Williamson contends that # there were no true larvae until after the establishment of classes in the respective phyla, # early animals hybridised to produce chimeras of parts of dissimilar species, # the Cambrian explosion resulted from many such hybridisations, # modern animal phyla and classes were produced by such early hybridisations, rather than by the gradual accumulation of specific differences.
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The prothallus harbours sporadic marginal archegonial cushions and this is where the archegonia are borne, while the antheridia are borne on slender branches on the basal margins of the prothallus. In the presence of water, spores germinate following a typical fern progression, with the antheridia trapped under the prothallus bursting to release the sperm cells. A chemical signal (sperm chemotaxis) is released from the archegonia which attracts the motile sperm cells towards it. Once the sperm cells reach the archegonium, they open and enable the male gamete to travel down to the ovum, with which it unites to induce fertilisation and form a zygote. This fertilised zygote is diploid and develops into an embryo and sporophyte, or ‘true fern’ that is most readily recognised, while remaining embedded in the prothallus.
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The term spore derives from the ancient Greek word σπορά spora, meaning "seed, sowing", related to σπόρος sporos, "sowing", and σπείρειν speirein, "to sow". In common parlance, the difference between a "spore" and a "gamete" is that a spore will germinate and develop into a sporeling, while a gamete needs to combine with another gamete to form a zygote before developing further. The main difference between spores and seeds as dispersal units is that spores are unicellular, the first cell of a gametophyte, while seeds contain within them a developing embryo (the multicellular sporophyte of the next generation), produced by the fusion of the male gamete of the pollen tube with the female gamete formed by the megagametophyte within the ovule. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes.
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