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The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
Sexual size dimorphism varies among taxa, with males typically being larger, though this is not always the case, e.g. birds of prey, hummingbirds, and some species of flightless birds. [ 67 ] [ 68 ] Plumage dimorphism, in the form of ornamentation or coloration, also varies, though males are typically the more ornamented or brightly colored sex ...
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 ...
Some species (including humans) have a gene SRY on the Y chromosome that determines maleness. Members of SRY-reliant species can have uncommon XY chromosomal combinations such as XXY and still live. [9] Human sex is determined by the presence or absence of a Y chromosome with a functional SRY gene.
“Gender identity is how you feel about yourself and the ways you express your gender and biological sex,” says Golob. Meanwhile, sexuality refers to who you are emotionally, physically ...
A human egg contains only one set of chromosomes (23) and is a haploid. Sperm also have only one set of 23 chromosomes and are therefore haploid. When an egg and sperm fuse at fertilization, the two sets of chromosomes come together to form a unique diploid individual with 46 chromosomes. [2]
In that view, many human artifacts could be considered subject to sexual selection as part of the extended phenotype, for instance clothing that enhances sexually selected traits. [2] During human evolution, on at least two occasions, hominid brain size increased rapidly over a short period of time followed by a period of stasis.
Mammals (including humans [21] [22]) and birds are solely gonochoric. [23] and Tardigrades are almost always gonochoric. [24] Seventy-five percent of snails are gonochoric. [25] Most arthropods including a majority of crustaceans are gonochoric. [26] [27] In animals, sex is most often genetically determined, but may be determined by other ...