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Polycyclic animals reproduce intermittently throughout their lives. Semelparous organisms reproduce only once in their lifetime, [27] such as annual plants (including all grain crops), and certain species of salmon, spider, bamboo and century plant. [28] Often, they die shortly after reproduction. This is often associated with r-strategists.
In order to reproduce sexually, both males and females need to find a mate. Generally in animals mate choice is made by females while males compete to be chosen. This can lead organisms to extreme efforts in order to reproduce, such as combat and display, or produce extreme features caused by a positive feedback known as a Fisherian runaway.
Again, however, this is not applicable to all sexual organisms. There are numerous species which are sexual but do not have a genetic-loss problem because they do not produce males or females. Yeast, for example, are isogamous sexual organisms which have two mating types which fuse and recombine their haploid genomes. Both sexes reproduce ...
Most organisms that create their offspring using sexual reproduction have two common sexes, males and females, and in other species, there are hermaphrodites, organisms that can function reproductively as either female or male, or both. [2] There are also some species in which only one sex is present, temporarily or permanently.
However, in sexual reproduction new organisms are formed by the fusion of haploid sperm and eggs resulting in what is known as the zygote. [1] Although animals exhibit both sexual and asexual reproduction the vast majority of animals reproduce by sexual reproduction. [1]
Apomixis occurs in many plant species such as dandelions (Taraxacum species) and also in some non-plant organisms. For apomixis and similar processes in non-plant organisms, see parthenogenesis . Natural vegetative reproduction is a process mostly found in perennial plants, and typically involves structural modifications of the stem or roots ...
Sexual selection creates colourful differences between sexes in Goldie's bird-of-paradise.Male above; female below. Painting by John Gerrard Keulemans.. Sexual selection is a mechanism of evolution in which members of one sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual ...
Labeled anatomy of the human vulva and nearby structures. The vulva is of all of the external parts and tissues and includes the following: [3] Clitoris: an organ located at the top of the vulva.