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Cryptic female choice is a form of mate choice which occurs both in pre- and post-copulatory circumstances in which females of certain species use physical or chemical mechanisms to control a male's success of fertilizing their ova or ovum; i.e. by selecting whether sperm are successful in fertilizing their eggs or not.
Genetic incompatibility describes the process by which mating yields offspring that are nonviable, prone to disease, or genetically defective in some way. In nature, animals can ill afford to devote costly resources for little or no reward, ergo, mating strategies have evolved to allow females to choose or otherwise determine mates which are more likely to result in viable offspring.
The mammalian female reproductive system contains three main divisions: the vagina and uterus, which act as the receptacle for the sperm, the ovaries, which produce the female's ova, and the vulva, which consists of the labia and clitoris. The vagina, uterus and ovaries are always internal while the vulva is external.
In cichlid fish, it has been found that increased sperm competition can lead to evolved larger sperm numbers, sperm cell sizes, and sperm swimming speeds. [ 49 ] In some insects and spiders, for instance Nephila fenestrate , the male copulatory organ breaks off or tears off at the end of copulation and remains within the female to serve as a ...
A sperm which contains an X chromosome, produced in the usual way in the testicles, referring to the occurrence of such a sperm fertilizing an egg and giving birth to a female. [1] A sperm which artificially contains genetic material from a female. [2] Since the late 1980s, scientists have explored how to produce sperm where all of the ...
Arumala adds that there is currently no way to test the quality of a person’s eggs at the time they freeze them. “The only testing done is to see whether or not the eggs are mature enough for ...
When couples use reproductive assistance like IVF to get pregnant, it can also feel isolating, Gur says. "Women doing IVF for many years speak to loneliness being the most painful part of the ...
The presence of milk production in caecilians that lay eggs suggests an evolutionary transition between egg-laying and live birth. [ 36 ] [ 37 ] [ 38 ] Another well known example of nourishing young with secretions of glands is the crop milk of certain birds such as columbiform birds (pigeons and doves), among others.