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21-456: The population of Karakat block increased from 179,195 in 2001 to 209,284 in 2011, a 16.8% increase. This was a slightly decadal lower growth rate than the average of Rohtas district. As of 2011, Karakat block had a sex ratio of 920 females for every 1000 males, which was about average for Rohtas district. The ratio was slightly higher among the 0-6 age group, with 926 females for every 1000 males. There were 37,804 members of scheduled castes in

42-479: A few plover species is clearly related to a strongly male-biased adult sex ratio. Those species with male care and polyandry invariably have adult sex ratios with a large surplus of males, which in some cases can reach as high as six males per female. Male-biased adult sex ratios have also been shown to correlate with cooperative breeding in mammals such as alpine marmots and wild canids . This correlation may also apply to cooperatively breeding birds, though

63-411: Is a field of academic study which seeks to understand the sex ratios observed in nature from an evolutionary perspective. It continues to be heavily influenced by the work of Eric Charnov . He defines five major questions, both for his book and the field in general (slightly abbreviated here): Biological research mostly concerns itself with sex allocation rather than sex ratio, sex allocation denoting

84-460: Is of particular interest to anthropologists and demographers. In human societies, sex ratios at birth may be considerably skewed by factors such as the age of mother at birth and by sex-selective abortion and infanticide . Exposure to pesticides and other environmental contaminants may be a significant contributing factor as well. As of 2024, the global sex ratio at birth is estimated at 107 boys to 100 girls (1,000 boys per 934 girls). By old age,

105-567: The American Academy of Arts and Sciences . Two of his papers are Science Citation Classics. Charnov gained his B.S. in 1969 from the University of Michigan and his PhD in evolutionary ecology from the University of Washington in 1973. He is a Distinguished Professor (Emeritus) of Biology at the University of New Mexico and the University of Utah . His research interests are: metabolic ecology (temperature and body size in

126-404: The noisy miner where females always disperse. Humans: Institutions: Eric Charnov Eric Lee Charnov (born October 29, 1947) is an American evolutionary ecologist . He is best known for his work on foraging , especially the marginal value theorem , and life history theory , especially sex allocation and scaling/allometric rules. He is a MacArthur Fellow and a Fellow of

147-546: The 1:1 ratio is the evolutionarily stable strategy (ESS). This ratio has been observed in many species, including the bee Macrotera portalis . A study performed by Danforth observed no significant difference in the number of males and females from the 1:1 sex ratio. Spending equal amounts of resources to produce offspring of either sex is an evolutionarily stable strategy : if the general population deviates from this equilibrium by favoring one sex, one can obtain higher reproductive success with less effort by producing more of

168-429: The allocation of energy to either sex. Common research themes are the effects of local mate and resource competition (often abbreviated LMC and LRC, respectively). Fisher's principle (1930) explains why in most species, the sex ratio is approximately 1:1. His argument was summarised by W. D. Hamilton (1967) as follows, assuming that parents invest the same whether raising male or female offspring: In modern language,

189-454: The block, representing 18.06% of the population, which was about average for Rohtas district. Members of scheduled tribes in the block numbered 455, or 0.22% of the population, which was somewhat lower than the district average 1.12%. The literacy rate in Karakat block was 73.94%, which was lower than the district average of 73.37%. Literacy was higher in men (85.26%) than in women (61.61%);

210-468: The corresponding 23.65% gender gap was the highest in Rohtas district. A majority of the population of Karakat block is employed in agriculture . In 2011, 24.97% of the workforce was employed as cultivators who owned or leased their own land, and 46.82% of the workforce was employed as agricultural labourers who worked someone else's land for wages. A further 8.81% was employed as household industry workers,

231-549: The evidence is less clear. It is known, however, that both male-biased adult sex ratios and cooperative breeding tend to evolve where caring for offspring is extremely difficult due to low secondary productivity, as in Australia and Southern Africa . It is also known that in cooperative breeders where both sexes are philopatric like the varied sittella , adult sex ratios are equally or more male-biased than in those cooperative species, such as fairy-wrens , treecreepers and

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252-424: The highest proportion in Rohtas, and the remaining 17.97% were engaged in other forms of work. All 128 inhabited villages in Karakat block, including Karakat itself, have access to clean drinking water , but none have tap water ; instead, water is supplied by well and hand pump . 103 of the villages (80.47%) had schools , which served 94.14% of the block's population. 61 had medical facilities, serving 59.37% of

273-413: The male fish dies, the strongest female changes its sex to become the male for the group. All of these wrasses are born female, and only become male in this situation. Other species, like clownfish, do this in reverse, where all start out as non-reproductive males, and the largest male becomes a female, with the second-largest male maturing to become reproductive. Traditionally, farmers have discovered that

294-434: The most economically efficient community of animals will have a large number of females and a very small number of males. A herd of cows with a few bulls or a flock of hens with one rooster are the most economical sex ratios for domesticated livestock. It was found that the amount of fertilizing pollen can influence secondary sex ratio in dioecious plants. Increase in pollen amount leads to decrease in number of male plants in

315-829: The other. For species where the cost of successfully raising one offspring is roughly the same regardless of its sex, this translates to an approximately equal sex ratio. Bacteria of the genus Wolbachia cause skewed sex ratios in some arthropod species as they kill males. Sex-ratio of adult populations of pelagic copepods is usually skewed towards dominance of females. However, there are differences in adult sex ratios between families: in families in which females require multiple matings to keep producing eggs, sex ratios are less biased (close to 1); in families in which females can produce eggs continuously after only one mating, sex ratios are strongly skewed towards females. Several species of reptiles have temperature-dependent sex determination , where incubation temperature of eggs determines

336-656: The overall block population had access to electricity. Karakat block has 128 inhabited villages and 22 uninhabited ones, for a total of 150 villages: Sex ratio A sex ratio is the ratio of males to females in a population . As explained by Fisher's principle , for evolutionary reasons this is typically about 1:1 in species which reproduce sexually . However, many species deviate from an even sex ratio, either periodically or permanently. Examples include parthenogenic and androgenetic species, periodically mating organisms such as aphids, some eusocial wasps , bees , ants , and termites . The human sex ratio

357-507: The population, which was above the Rohtas district average of 35.63% served by medical facilities. 36 villages had post offices . 60 villages had telephone service, serving 62.11% of the block's population; this was about average for Rohtas district. 72 villages had transport communications (bus, rail , or navigable waterways). 20 villages had banks , and 19 had agricultural credit societies . 82 villages had pucca roads . 118 villages, Karakat among them, had access to electricity ; 89.47% of

378-440: The progeny. This relationship was confirmed on four plant species from three families – Rumex acetosa ( Polygonaceae ), Melandrium album (Caryophyllaceae), Cannabis sativa and Humulus japonicus ( Cannabinaceae ). In charadriiform birds, recent research has shown clearly that polyandry and sex-role reversal (where males care and females compete for mates) as found in phalaropes , jacanas , painted snipe and

399-485: The sex of the individual. In the American alligator , for example, females are hatched from eggs incubated between 27.7 to 30 °C (81.9 to 86.0 °F), whereas males are hatched from eggs 32.2 to 33.8 °C (90.0 to 92.8 °F). In this method, however, all eggs in a clutch (20–50) will be of the same sex. In fact, the natural sex ratio of this species is five females to one male. In birds, mothers can influence

420-414: The sex of their chicks. In peafowl , maternal body condition can influence the proportion of daughters in the range from 25% to 87%. Dichogamy (sequential hermaphroditism) is normal in several groups of fish, such as wrasses , parrotfish and clownfish . This can cause a discrepancy in the sex ratios as well. In the bluestreak cleaner wrasse , there is only one male for every group of 6-8 females. If

441-405: The sex ratio reverses, with 81 older men for every 100 older women; across all ages, the global population is nearly balanced, with 101 males for every 100 females. In most species, the sex ratio varies according to the age profile of the population. It is generally divided into four subdivisions: These definitions can be somewhat subjective since they lack clear boundaries. Sex ratio theory

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