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Topic: Sex ratio

	Evolution - Sex Ratios
		The queen is equally related to her sons and daughters, and hence should favor a 1:1 sex ratio.
		Seychelles warblers adjust the primary sex ratio facultatively in response to the quality of the territory they inhabit and to the number of helpers present on the breeding territories.
		Cytoplasmically inherited factors that skew sex allocation towards females are known from a variety of plants and animals.
	core.ecu.edu /biol/summersk/summerwebpage/biol3520/EVOLsexratios.htm (893 words)

	Punjab Environment Information Web Portal. ENVIS Centre Punjab, on State Environment Issues
		Sex ratio is an important component of population structure.
		Sex ratio defined as number of females per 1000 males in the population, it is an important indicator to measure the extent of prevailing equity between males and females in a society at a given point of time(Source:www.censusindia.net).
		Abortion of female foetus, sex determination tests, low status of girls and women in rural areas and less attention in upbringing and health facilities to females are the main reasons for lowest sex ratio in Punjab.
	www.punjabenvironment.com /demo_sexratio.htm (394 words)

	Betta Splendens - Half Moon, Double Tail, Crown Tail Bettas - Sex Ratio Distortion
		While we are conditioned to believe this to be "normal" by virtue of the 1:1 sex ratio in humans, we are all familiar with social insects like ants and termites that display quite different sex ratios.
		When sex ratios are far from 1:1 there is a real advantage to producing an excess of the limited sex, albeit an advantage that will eventually be eliminated.
		If Betta have the biological capacity to adjust sex ratio, then they need only to be able to assess the size of their mates to manipulate it adaptively.
	www.bettysplendens.com /articles/page.imp?articleid=1248 (0 words)

	China's missing girls
		The long-term global survey showed that the sex ratio at birth is quite stable, generally between 103 and 107.
		This figure combines with subsequent mortality figures at different ages to decide the sex ratio among the population, which then directly influences marriage patterns, family structure and the economy.
		The sex ratio among the first-baby group is quite normal but it increases abruptly among the second-baby group, and it's much higher among the third-baby group according to the report.
	app1.chinadaily.com.cn /star/2002/1024/fo5-1.html (538 words)

	News - The sex ratio distortion in the human head louse is conserved over time
		Conclusions: Regardless of its origin, this sex ratio distortion in head lice that has been reported world wide, is stable over time and is a remarkable deviation from the stability of frequencydependent selection of Fisher's sex ratio.
		Records of sex ratios in human head lice in Britain [2,3], Kenya [3,4], Tanzania, Colombia, Australia [3], Nigeria, Ceylon, Palestine [4], India [4,5], and North America [6] show ~65% of the adult lice to be Page 1 of 13 (page number not for citation purposes) BMC Genetics 2004, 5 female.
		Sex ratio distortions in arthropods frequently originate from cytoplasmic or extrachromosomal factors and parasites of the host and are most often associated with the endosymbiont Wolbachia pipientis.
	www.headlice.org /news/2004/sexratio.htm (784 words)

	Skewed Sex Ratio of Births in India May Be the Result of Sex-Selective Abortion (Site not responding. Last check: )
		However, among families that already had one child, the sex ratio for the second birth differed dramatically, depending on whether the last child born had been a girl or a boy (759 vs. 1,102, respectively), a pattern that was apparent in all but one of the 17 Indian states included in the study.
		Sex ratios for second births did not differ by the mother's religion, the family's land holdings or whether the family lived in an urban area.
		The low sex ratio observed in the study, they say, reflects a cultural preference for male children, who not only carry on the family name but generally earn more money than females and are better able to financially support their parents during the latter's final years (India does not have a social security program).
	www.guttmacher.org /pubs/journals/3210206b.html (834 words)

	Sex ratio - Biocrawler (Site not responding. Last check: )
		Sex ratio is the ratio of males to females in a population.
		Fisher posited that the sex ratio is genetically determined, there being many possible ratios.
		The bacterium wolbachia causes skewed sex ratios as it kills males through kin selection.
	www.biocrawler.com /encyclopedia/Sex_ratio (158 words)

	Indian population by age & sex,age-sex ration in India,Indian Population,Population of India,Indian Census ... (Site not responding. Last check: )
		Sex ratio (the number of females per 1000 males) for India is 933 females per 1000 males.
		India's sex ratio at brith: 976/1000 in 1961 to 927/1000 in 2001.
		The availability of technology to determine the sex of the foetus and the practice of aborting a female foetus are given as the reasons for such adverse sex ratios.
	finance.indiamart.com /india_business_information/india_age_sex_population_ration.html (204 words)

	Migration Information Source - Sex Ratios of the Foreign Born in the United States (Site not responding. Last check: )
		The male-to-female sex ratio is calculated by dividing the number of males (of all ages) by the number of females (of all ages) and multiplying by 100.
		In 2002, the sex ratios of the foreign born from India (138) and Mexico (124) were well above 100, indicating a higher number of males than females in the population (see Graph 2).
		As the average age of the immigrant population increases, and a higher proportion of the foreign born are in the older age groups, the number of females relative to males increases, lowering the sex ratio.
	www.migrationinformation.org /USFocus/display.cfm?ID=100 (871 words)

	Is maternal malnutrition associated with a low sex ratio at birth? Human Biology - Find Articles
		Sex ratio at birth, the number of males per 100 females, shows ethnic and geographic variations, from under 100 in fl African populations to over 110 in Asian populations (Ruder 1986).
		The aim of this study is to analyze the sex ratio at birth in relation to the nutritional status of women in a rural African society.
		Sex ratio at birth was directly related to maternal height, from 100 among the shortest quartile to 125 in the tallest quartile (p
	www.findarticles.com /p/articles/mi_qa3659/is_199812/ai_n8824309 (914 words)

	India Together: Missing males lifts the overall sex ratio - April 2004
		During the final decade of the last millennium, the Child Sex Ratio (CSR, the number of girls in the age group of 0 to 6 years per thousand boys of the same age group) recorded its highest fall, dropping 18 points from 945 to 927.
		This breakdown, therefore, offers a clue: that the reversal of the sex ratio is not due to improved conditions for women, but something else that is causing the numbers of men to go down.
		An excessive focus on the sex ratio, therefore, is likely to conceal horrors at both ends of the spectrum - with female foetuses and girls being killed at one end, and men falling victim to illnesses at the other end.
	www.indiatogether.org /2004/apr/hlt-csratio.htm (1588 words)

	An evolutionary account of sex-ratios:
		Biological mechanisms that have been argued to cause such changes in sex ratio are usually environmental in explanation, e.g., hormonal changes, time of fertilization in relation to ovulation, temperature of ovum, foetal reabsorption, and developmental pace of male and female fetuses (Van Hooff, 1997; James, 1987).
		Chacon-Puignau and Jaffe (1997) found, that in Venezuela, sex ratio at birth (SRB), as well as fetal and infant deaths, were related to economic and marital conditions.
		These results suggest that the ratios found in populations of cercopithecine primates are indeed strongly selected for in order to both maintain a consistent group size that doesn’t lay waste to local resources, as well as avoid inbreeding depression.
	www.u.arizona.edu /~jons/sexratio.html (3571 words)

	Sex Ratio (Site not responding. Last check: )
		Sex Ratio is the ratio of male members of a population to female members.
		Say the sex ratio is genetically determined, there being many possible ratios.
		The Price-to-Earnings ratio of a stock is a number calculated from the price per share of the stock divided by the earnings per share of that stock for the past 12 months.
	www.serebella.com /encyclopedia/article-Sex_Ratio.html (271 words)

	Reduced Ratio of Male to Female Births
		To assess whether shifts in the ratio of males to females born, defined as the sex ratio, constitute a sentinel health event, it is necessary to determine the expected pattern of sex ratio in light of known modifying conditions.
		Sex ratio is measured as the ratio of male to female births.
		Known causes of altered sex ratio, such as older age of father, use of in vitro fertilization and stress of mothers, appear unlikely to account for trends that have persisted throughout the past 2 decades.
	www.whensmokeranlikewater.com /publications/scientific/Sex_Ratio.htm (3987 words)

	Regional Pattern of Sex Ratio in Karnataka
		The sex composition is of paramount important in any population because of contrasting and complementary roles played by two sexes in economy and society.
		This ratio has a preformed important not only in demographic factors like fertility, mortality, migration etc but also on other factors like manpower, national income, education, housing etc. hence proper understanding of the sex composition of any population is essential.
		Sex ratio of the advanced countries is always more in favour females where as the trend is reverse in case of the LDCs.
	www.ourkarnataka.com /Articles/sexratio.htm (663 words)

	Sex-selective abortion and infanticide at AllExperts
		However, there is a strong imbalance in sex ratios in China as well as Japan, India, and Taiwan, probably the result of sex-selective abortion.
		The female-to-male sex ratio is even lower in cases where a couple has had a previous daughter, but no sons, dropping to 759 to 1000 for the second child if the first was a daughter, and 719 to 1000 for a third child if the first two were both daughters.
		Today's concentrations of sex ratios imbalances are regional -in North-West India or East China- and demographic -among women whose first child was a girl and do not correspond at all to known epidemiological features.
	en.allexperts.com /e/s/se/sex-selective_abortion_and_infanticide.htm (1622 words)

	BioMed Central \| Full text \| The sex ratio distortion in the human head louse is conserved over time
		Records of sex ratios in human head lice in Britain [2,3], Kenya [3,4], Tanzania, Colombia, Australia [3], Nigeria, Ceylon, Palestine [4], India [4,5], and North America [6] show ~65% of the adult lice to be female.
		A sex ratio bias is often more likely related to the physiological state of its host and is consequently not directly controlled by the mother [36].
		In the analysis and interpretation of sex ratio deviations, the discrimination between primary sex ratio and functional sex ratio is pivotal [37].
	www.biomedcentral.com /1471-2156/5/10 (4870 words)

	Understanding deer sex ratios: Whitetail Stewards, Inc.
		The sex ratio is a number describing the number of adult females for each adult male in a population.
		These are the ratios biologists most often refer to, and they should not be confused with observed or post-hunt ratios as the latter are nearly always heavily skewed towards females.
		Ideally, the sex ratio of a deer herd should be as close to 1:1 as possible, but this is difficult to achieve.
	www.whitetailstewards.com /articlesonsite/deerpopulationmanage/understandingdeersexratios.htm (856 words)

	Declining Sex Ratio in a First Nation Community (Site not responding. Last check: )
		The birth sex ratio (male:female) of a population is often reported as the male proportion (m = number of male births divided by the total of all births).
		The initial assessment of the sex ratios of the Aamjiwnaang community over the 20-year period 1984-2003 presented here indicates that there is a significant ongoing decrease in the proportion of male live births beginning in the early 1990s and continuing to the end of the study period 2003.
		Although several potential factors may be contributing to the observed decrease in sex ratio, the close proximity of this community to the large aggregation of petrochemical industry and potential exposures to compounds that may influence sex ratios warrants further assessment into the types of chemical exposures for this population.
	www.ehponline.org /members/2005/8479/8479.html (3859 words)

	Tools of the Trade - Sex Ratios for Analyzing Mortality Data
		A common approach to revealing the role of sex in mortality is to list death rates by cause and sex in order of their sex ratio.
		First and foremost, the sex ratio is based on the assumption that the population being observed is equally divided between males and females.
		Sex ratios are convenient and effective tools but may be misleading or provide incomplete information when presented without other vital statistics.
	www.health.state.pa.us /HPA/Stats/techassist/sexratio.htm (788 words)

	NPWRC :: Impact of Red Fox on Mallards
		Of particular importance is that the sex balance of canvasback populations does not tend to be restored by hunting.
		At P= 1.3, the asymptotic sex ratio is 186:100 if recruitment to the spring population is 1.0 young of each sex per adult female, a reasonable level in a stable population.
		The authors attributed the change between the secondary sex ratio and the quaternary ratio to heightened mortality of males resulting from greater loss to predators, hunters, and perhaps parasites.
	www.npwrc.usgs.gov /resource/mammals/sexratio/other.htm (864 words)

	The President's Council on Bioethics: Beyond Therapy: Biotechnology and the Pursuit of Human Improvement
		The standard sex ratio at birth is 105 baby boys born for every 100 baby girls, but in many countries today the ratio is upwards of 120 baby boys born for every 100 girls.
		The sex ratio in Venezuela is 107.5, in Yugoslavia 108.6, in Egypt 108.7, in Hong Kong 109.7, in South Korea 110, in Pakistan 110.9, in Delhi, India 117, in China 117, in Cuba 118, in the Caucuses nations of Azerbaijan, Armenia, and Georgia, the sex ratio has reached as high as 120.
		The two aspects of sex control – it is control of sex, and it is a form of control of offspring – locate the deeper significance of this practice in two important human contexts: the meaning of sexuality, and the nature of procreation and family relations.
	www.bioethics.gov /background/sex_control.html (7435 words)

	Our Stolen Future: Changes in sex ratio
		Usually, the sex ratio (numbers of boys born divided by the numbers of girls born) is slightly greater than one.
		Most recently, public health scientists in Canada have reported a sharp drop in the sex ratio of a First Nation community (Chippewa) near Sarnia, Ontario, a heavily industrialized region with the province.
		Paternal concentrations of dioxin and sex ratio of offspring.
	www.ourstolenfuture.org /NewScience/reproduction/sexratio/sexratio.htm (0 words)

	2006-10-03 Sex Ratio
		To be able to determine the sex ratio precisely, you have to have a sufficiently large population.
		The conflict between core genes and mitochondrial genes in the group of sons does not on an evolutionary timescale lead to a stable balance, which is the explanation for the variable sex ratio.
		The sex of the nettle is therefore determined by the genes.
	www.leidenslatest.leidenuniv.nl /index.php3?m=1&t=4&link_url=http://www.research.leidenuniv.nl&link_id=230&link_extern=1 (920 words)

	Sex ratio and Wolbachia infection in the ant Formica exsecta
		Sex ratio and Wolbachia infection in the ant Formica exsecta
		In that population sex ratio was highly male biased and only a minority of nests (11%) produced females (Brown and Keller, 2000; Brown and Keller submitted).
		One is proximate constraints arising from the mechanism of sex determination in ants (Wenseleers and Billen, 2000).
	www.nature.com /hdy/journal/v87/n2/full/6889180a.html (3955 words)

	Sex ratio manipulation of parasitoids
		Deriving behavioral rules regarding sex allocation is futile unless the parasitoid is known to directly manipulate sex ratios.
		Host selection and sex ratio manipulation have been and continue to be widely studied and new research ought to expand from laboratory experiments by observing and experimenting in real life natural settings.
		Sex ratio manipulation by the parasitoid wasp Spalangia cameroni in response to host age: a test of the host-size model.
	www.msu.edu /user/miller20/lee.htm (3045 words)

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