Barratt, Sperm selection in natural conception: what can we learn from Mother Nature to improve assisted reproduction outcomes? In natural conception only a few sperm cells reach the ampulla or the site of fertilization. This population is a selected group of cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies ART utilize a more random sperm population.
An extraordinary battle between sperm whales and orcas – in pictures
Sperm Whale | NOAA Fisheries
I spent last week on a six-metre fishing boat in the Indian Ocean off Kalpitiya, on the west coast of Sri Lanka with the photographer Andrew Sutton and the marine biologist Ranil Nanayakkara. Andrew and I were diving in a marine conservation area under special licence from the Sri Lankan wildlife department. Here, I met a pair of young, sexually mature male sperm whales — cetacean teenagers. Facebook Twitter Pinterest.
Killer sperm: Sexual ‘arms race’ takes its toll on females
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg  during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males' chance of reproductive success. Sperm competition is often compared to having tickets in a raffle ; a male has a better chance of winning i.
Low sperm count means that the fluid semen you ejaculate during an orgasm contains fewer sperm than normal. A low sperm count is also called oligospermia ol-ih-go-SPUR-me-uh. A complete absence of sperm is called azoospermia.