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Obligate parthenogenesis is the process in which organisms exclusively reproduce through asexual means. [39] Many species have been shown to transition to obligate parthenogenesis over evolutionary time. Well documented transitions to obligate parthenogenesis have been found in numerous metazoan taxa, albeit through highly diverse mechanisms.
Asexual reproduction in liverworts: a caducous phylloid germinating. Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single ...
Sexual selection in birds. Male greater frigatebird displaying. Sexual selection in birds concerns how birds have evolved a variety of mating behaviors, with the peacock tail being perhaps the most famous example of sexual selection and the Fisherian runaway. Commonly occurring sexual dimorphisms such as size and color differences are ...
Parthenogenesis in squamates. Parthenogenesis is a mode of asexual reproduction in which offspring are produced by females without the genetic contribution of a male. Among all the sexual vertebrates, the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in squamate ...
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 biological 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 ...
The songs of birds, insects and many other animals are part of a ritual to attract potential partners of their own species. The song presents specific patterns recognizable only by members of the same species, and therefore represents a mechanism of reproductive isolation. This recording is the song of a species of cicada, recorded in New Zealand.
Trematoda is a class of flatworms known as flukes or trematodes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host, where the flukes sexually reproduce, is a vertebrate.
Regeneration in biology is the process of renewal, restoration, and tissue growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. [ 1 ] Every species is capable of regeneration, from bacteria to humans. [ 2 ][ 3 ][ 4 ] Regeneration can either be complete [ 5 ...