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वीडियो न देखे sex in sexually reproducing organisms. For the act, see Sexual intercourse. For other uses, see Sex (disambiguation). Part of a series on Sex X Y chromosome.jpg Biological terms Sexual dimorphism Sexual differentiation Feminization Virilization Sex-determination system XY X0 ZW Z0 Temperature-dependent Haplodiploidy Heterogametic sex Homogametic sex Sex chromosome X chromosome Y chromosome Testis-determining factor Hermaphrodite Sequential hermaphroditism Intersex Sexual reproduction Evolution of sexual reproduction Anisogamy Isogamy Germ cell Meiosis Gametogenesis Spermatogenesis Oogenesis Gamete spermatozoon ovum Fertilization External fertilization Internal fertilization Sexual selection Plant reproduction Fungal reproduction Sexual reproduction in animals Sexual intercourse Copulation Human reproduction Sexuality Plant sexuality Animal sexuality Human sexuality Mechanics Differentiation Activity Sexual orientation - 4 symbols.svg Sex portal Issoria lathonia.jpg Biology portal vte Organisms of many species are specialized into male and female varieties, each known as a sex. Many animals and some plants have differences between the male and female sexes in size and appearance, a phenomenon called sexual dimorphism. Sex differences in humans include, generally, a larger size and more body hair in men; women have breasts, wider hips, and a higher body fat percentage. In other species, the differences may be more extreme, such as differences in coloration or bodyweight. Sexual dimorphisms in animals are often associated with sexual selection – the competition between individuals of one sex to mate with the opposite sex.[42] Antlers in male deer, for example, are used in combat between males to win reproductive access to female deer. In many cases the male of a species is larger than the female. Mammal species with extreme sexual size dimorphism tend to have highly polygynous mating systems—presumably due to selection for success in competition with other males—such as the elephant seals. Other examples demonstrate that it is the preference of females that drive sexual dimorphism,