Sperm Competition
🔞 ALL INFORMATION CLICK HERE 👈🏻👈🏻👈🏻
Sperm Competition
Browse
Search
Login
Subscribe Now
Give Feedback
External Websites
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Martin Luther King, Jr. | Biography, Speeches, Facts, & Assassination
Adolf Hitler | Biography, Rise to Power, & Facts
Kamala Harris | Biography, Policies, Family, & Facts
Albert Einstein | Biography, Education, Discoveries, & Facts
Get a Britannica Premium subscription and gain access to exclusive content.
Subscribe Now
animal social behaviour: Social interactions involving sex
…time is known as “sperm competition.” The potential for overlap between the sperm of different males within the female has resulted in a diversity of behavioral adaptations and bizarre male strategies for maximizing paternity. Sperm competition , for example, is thought to be the primary reason why males offer nuptial…
Competition , in ecology, utilization of the same resources by organisms of the same or of different species living together in a community, when the resources are not sufficient to fill the needs of all the organisms. Within a species, either all members obtain part of a necessary resource such as food…
Sperm , male reproductive cell, produced by most animals. With the exception of nematode worms, decapods (e.g., crayfish), diplopods (e.g., millipedes), and mites, sperm are flagellated; that is, they have a whiplike tail. In higher vertebrates, especially mammals, sperm are produced in the testes. The sperm…
Sign up here to see what happened On This Day , every day in your inbox!
By signing up, you agree to our Privacy Notice .
Inspire your inbox –
Sign up for daily fun facts about this day in history, updates, and special offers.
By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica.
Click here to view our Privacy Notice . Easy unsubscribe links are provided in every email.
©2021 Encyclopædia Britannica, Inc.
Sperm competition , a special form of mating competition that occurs in sexual species when females accept multiple mating partners over a relatively short period of time. The potential for overlap between the sperm of different males within the female has resulted in a diversity of behavioral adaptations and bizarre strategies for maximizing paternity.
Sperm competition is thought to be the primary reason why males offer nuptial gifts (such as food) to females or allow females to cannibalize them. Such nuptial gifts are best thought of as mating effort (that is, effort directed at increasing the number of offspring a male sires), because they are usually not available at the time of birth or hatching to benefit the offspring sired by the male presenting the gift. The male’s paternity and the number of sperm he transfers often correlate with the size of the donation, suggesting that the donation functions to increase the number of offspring he sires.
Sperm competition favours the evolution of paternity guards or mechanisms that reduce the impact of the mating efforts of competitors. In many animals , sperm competition results in mate-guarding behaviour, whereby males remain near the female following mating. This behaviour is designed to keep additional mates away from the female prior to the fertilization of her eggs. For example, in the cobalt milkweed beetle ( Chrysochus cobaltinus ), the male rides on the back of the female for several hours. By engaging in this behaviour, the male sacrifices time he could use to locate a new mate in favour of preventing her from copulating with other males before she can lay her eggs. In addition, male damselflies and dragonflies (order Odonata) use their genitalia to physically remove or compact the sperm of the female’s prior mates before they inseminate her with their own sperm.
Examples of sperm competition in polygynandrous vertebrates are found in dunnocks ( Prunella modularis ) and acorn woodpeckers ( Melanerpes formicivorus ). In dunnocks, a common English backyard bird, males peck at the female’s cloaca . This activity causes her to release a droplet of semen containing the sperm of prior mates before a new male begins to mate with her. In acorn woodpeckers, the threat to a male’s paternity comes from other males within the same breeding group. As a result, males spend virtually all their time within a few metres of fertile females, guarding them from other breeding males in the group. Birdsong and territorial behaviour have also been shown to function as paternity protection, although these behaviours have other primary functions.
What is SPERM COMPETITION ? What does SPERM COMPETITION mean? - YouTube
Sperm competition | biology | Britannica
Sperm Competition Influences Testicle Size
Sperm Competition in Humans: Mate Guarding Behavior Negatively...
Sperm competition between brothers and female choice on Vimeo
When Sperm Compete, Nature’s Call Leads to Bigger … Testicles
Success in the living world is all about reproduction. Sperm competition has caused primate testicle size to increase.
[ In humans, the testes] are from an inch and a half to two inches long, about an inch and a quarter from the anterior to the posterior border, and nearly an inch from side to side. The weight of each varies from three-quarters of an ounce to an ounce, and the left is often a little the larger of the two.
S uccess in the living world is all about reproduction. For living animals with internal fertilization (i.e., within the female’s body), reproductive success is determined by many factors, one of which is males’ ability to fertilize females’ ova (eggs). This depends not only on a male identifying a mate, engaging in copulatory behavior (sex), and inseminating a female, but also on what happens after copulation and insemination, especially when there is sperm competition .
F emales only require the healthy sperm of one male to put them on the path to reproductive success; however, depending on the species’ mating system, females may copulate with more than one male during or around the time they are ovulating (producing mature eggs). A species’ mating system depends in part on female mate choice—how she chooses mates, which ones she chooses, and how many she chooses.
G et our newsletter with new stories delivered to your inbox every Friday.
I f a female chooses to mate with more than one male during her ovulatory cycle, sperm competition, in which the males’ sperm compete to fertilize the female’s ovum, may ensue. Species in which females commonly have multiple male partners, such as chimpanzees and bonobos, tend to have higher rates of sperm competition. Species prone to monogamy, like gibbons, or in which multiple adult females tend to mate with a single male, like gorillas, tend to have lower sperm-competition rates.
O ver generations, selection should enhance both males’ ability to inseminate females and their odds of successful paternity, especially when there is risk of sperm competition. So how does nature adapt when males need to ensure that their sperm are the sperm?
O ne potential solution to the problem is to make more sperm—the more sperm one has compared to a competitor, the better the odds of successful fertilization. Increased sperm production requires more massive sperm factories, or testicles. So larger testes mean more sperm, greater reproductive success, and, likely, offspring with relatively larger testicles, too. Thus, male chimpanzees and bonobos have evolved relatively large testicles compared to their body size, whereas gorillas and gibbons have relatively smaller testicles.
The 19th-century anatomist Jones Quain dissected the human testes, as illustrated by this engraving. Quain’s Elements of Anatomy
T he relative size of human testes is intermediate between traditionally monogamous and polygamous species. Many researchers have used this as evidence of some degree of sperm competition in humans, inferring something other than monogamy for the species.
R ecently, scientists have shown that certain traits of human sperm, such as sperm concentration, speed, and rates of abnormality, are more similar to gorillas’ sperm than to chimps’, which suggests low sperm competition in humans. It could be that modern humans’ relative testis size does not correlate with modern levels of sperm competition; risk of sperm competition and/or testis size may have changed over the course of human evolution. It could also be the case that relatively large testicles provide another, not yet fully understood, benefit to modern Homo sapiens males.
The testes of a male vervet monkey are relatively large for the primate’s body size. Vervets live in multi-male, multi-female groups. Bjørn Christian Tørrissen/ Wikimedia Commons
I t turns out there is a relationship between testis size in primates and genome evolution. Alex Wong examined the genetic sequences of 55 primate species and compared the rates of substitutions (changes in the “letters” of the DNA) in the sequences to the weight of the animals’ testes. The study showed that primates with larger testes had higher rates of genome evolution, probably as a by-product of greater sperm production and competition (in other words, the more sperm produced, the greater the chances of a mutation in the DNA sequence). Genetic mutation is one of the primary mechanisms of evolution—without variation in a population, natural selection cannot act.
This schematic of a howler monkey’s vocal tract shows the cup-shaped hyoid bone of an adult male Bolivian red howler monkey ( Alouatta sara ). Howler monkeys produce powerful roars, which may function to ward off males from other groups. (Red, hyoid; green, larynx; pink, tongue; dark gray, air sacs; brown, palate.) Dunn et al./ Cell
O n another note, a recent study found that species of howler monkeys with larger testes had smaller hyoids (the hyoid is a bone in the neck involved in producing vocalizations). “All howler monkey species have a highly modified larynx with a greatly enlarged cup-shaped hyoid bone containing an air sac, which is thought to function as a resonating chamber for their calls,” according to the authors. Therefore, species with smaller hyoids produced less amplified, or softer, vocalizations. What’s the connection to testes size? The hyoid-vocalization-testes combination reflects the monkeys’ social structure—a smaller hyoid, softer vocalizations, and larger testes equals more males in a group. The researchers hypothesize that with more males in a group, there is less of a need to ward off males from other groups with loud calls (in other words, there is strength in numbers). No need for loud calls? No need for a large hyoid. But, more males within a single group means greater potential for sperm competition, and thus larger testes.
A s the evolutionary biologist Ernst Mayr pointed out in his book The Growth of Biological Thought , “the crucial event in [Charles] Darwin’s mind, when reading [Thomas] Malthus’s statement on fertility [in the 1830s], was that he finally fully realized how important is the competition among individuals of the same species, and how entirely different the consequences of this competition are from typological competition among species .” But Darwin could not fathom at that time that competition among individuals extended to competition between individual sperm , as the process of how a sperm fertilizes an egg was not described for another two decades.
Caitlin Schrein earned a master’s and a doctorate in evolutionary anthropology from Arizona State University. She has conducted fieldwork searching for early primates in North America, monkeys in Europe, apes in Kenya, and the first hominins to leave Africa. Her doctoral research examined the relationship between human evolution education and students’ interest in science and their decision-making about social issues with a scientific basis, such as climate change. Schrein currently lives in Washington, D.C., where she works as a science writer and spends her free time going to museums, hanging out with her dogs, tweeting about fossils and evolution, and watching old movies.
An editorially independent magazine of the Wenner‑Gren Foundation for Anthropological Research Published in partnership with the University of Chicago Press
School Girl Fuck Porno
Private Hell
Larouge Lingerie
Double Penetration Oral
Cabela's Outdoor
