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The best-known case study involves the synchronization of menstrual cycles among women based on unconscious odor cues, the McClintock effect, named after the primary investigator, Martha McClintock, of the University of Chicago. [7] [8] A group of women were exposed to a whiff of perspiration from other women. Depending on the time in the month ...
In Western nations menstruation begins to affect females at 13 and menopause starts around 51. In non-industrialized countries, on the other hand, most females begin menstruation at a later age. [68] More lactation in the lifetime of non-western females inhibits ovulation and extends the number of fertile years. [69]
Whilst a vast number of studies have been conducted to investigate body odour and mating, research is now shifting in particular towards the effect of male scent to female sexual attraction. This is largely due to the effects of the menstrual cycle and hormone contraceptives, which directly affect women's partner preference. Past research has ...
The males with superior detection and flying abilities are most likely to reach the female beetle first which leads to a selection for genetically-advantageous males. [6] In most species, pheromones are released by the non-limiting sex. Some female moths signal, but this is cheap and low risk; it means the male has to fly to her, taking a high ...
As an alternative to natural sexual intercourse, there exists artificial insemination, where sperm is introduced into the female reproductive system without the insertion of the penis. [3] There are also many methods of assisted reproductive technology , such as in vitro fertilization , where one or more egg cells are retrieved from a woman's ...
In females, gametogenesis is known as oogenesis; this occurs in the ovarian follicles of the ovaries. This process does not produce mature ovum until puberty. In contrast with males, each of the original diploid germ cells or primary oocytes will form only one mature ovum, and three polar bodies which are not capable of fertilization.
Sperm competition is often compared to having tickets in a raffle; a male has a better chance of winning (i.e. fathering offspring) the more tickets he has (i.e. the more sperm he inseminates a female with). However, sperm are not free to produce, [7] and as such males are predicted to produce sperm of a size and number that will maximize their ...
Reproductive toxicants may adversely affect sexual function, ovarian failure, fertility as well as causing developmental toxicity in the offspring. [2] [3] Lowered effective fertility related to reproductive toxicity relates to both male and female effects alike and is reflected in decreased sperm counts, semen quality and ovarian failure.