The effect of female education on marital fertility in different size communities of Mexico

Based on a very large sample of married women aged 15 to 49 from the 1970 census of Mexico, the effect of literacy and education on the number of children ever born in different size communities is investigated. While cumulative marital fertility tends to be inversely related to community size, the overall shape of the education-fertility relationship is generally similar in rural, semi-urban, small urban, and large urban localities. These results combined with those for literacy do not support the hypothesis of an urbanization or a literacy threshold at which women's schooling begins to reduce family size. Literate wives have slightly more children than illiterate wives in rural areas, but in more urbanized regions this differential inverses and seems to widen with each increase in size of the community. Fertility is slightly higher at 1 to 3 years of primary school than at no education; it declines slightly at 4 to 5 years primary, and then declines substantially at complete primary, secondary, and preparatory/university levels. A statistically significant but small interaction between education and residence on cumulative marital fertility is noted. The overall greater impact of female education on cumulative marital fertility in urban as compared to semi-urban as compared to rural communities of Mexico is primarily due to the proportion of married women with fertility depressing educational backgrounds rather than to a markedly different effect of education, per se, on fertility. The results emphasize the country-wide importance of completion of the entire 6-year primary cycle.     

左炔诺孕酮和炔雌醚复合不育剂（EP-1）对雌性东方田鼠生殖的影响

  本文在实验室条件下通过一次性灌胃的方式研究了左炔诺孕酮-炔雌醚复合不育剂（EP-1）对雌性东方田鼠激素、生殖系统、胎仔数、受孕率的影响及药效持续时间,旨在检验其应用于野外东方田鼠不育控制的价值。结果表明,各浓度EP-1灌胃均能显著提高雌性东方田鼠的子宫系数,使子宫形态发生变化,对卵巢组织造成损伤,影响卵泡和黄体的发育,但是对雌二醇含量和子宫长度没有明显影响;60mg/kg EP-1灌胃能显著提高促卵泡刺激素含量和卵巢系数,而10mg/kg、30mg/kg EP-1灌胃对二者没有明显影响。室内繁殖实验表明,各浓度EP-1灌胃均能不同程度延迟初次怀孕时间,并降低试鼠的怀孕率和胎仔数,但抗生育作用具有可逆性且与药物浓度相关,10mg/kg、30mg/kg和60mg/kg剂量组生殖系统恢复时间分别为16 d、38 d和52 d。     

The effect of grazer size manipulation on periphyton communities

Summary We examined the effect of grazer size on periphyton biomass, size structure, and species compostion by removing the largest invertebrate grazers on artificial macrophytes planted in the littoral of Lake Memphremagog (Que-Vt). A series of exclosures with increasingly fine mesh prevented colonization by large invertebrates but allowed in smaller grazers. Oligochaetes, chironomids, and cladocerans effectively replaced snails so that total grazer biomass in the various treatments was not significantly different from the controls. With one exception, algal biomass, measured as chlorophyll a, did not differ significantly among the various treatments. However algal size and taxonomy were affected because the dominance of large blue-green colonies was apperantly related to the presence of large grazers. The results of the size manipulations were qualitatively similar to those induced in phytoplankton communities by size selective zooplankton grazing and are consistent with models based on general allometric equations.Contribution 181 of the Lake Memphremagog Project, Limnology Research Centre     

The effect of paternal investment on female fertility intention in South Korea

Life history theory views reproduction as an outcome of resource allocation. The allocation of resources such as parental investments of time, energy and material resources involves trade-offs between number of offspring and timing of reproduction. Within the framework of mammalian parental investment, the outstanding feature of human reproduction is the high level of paternal care. Although empirical evidence suggests that human paternal investment may have evolved as a reproductive strategy to reduce infant and child mortality rates, the effects of actual paternal investment, including allocating time to child care, on female reproductive decisions have received relatively little attention. We examined the trade-off from two perspectives using a representative sample of married South Korean women aged 20–44 in 2005 (n=977). First, paternal investment in domestic labor, including child care and housework, was expected to be associated with women's preference regarding future reproduction. Second, relative paternal investment was expected to increase women's preference for future reproduction, especially among employed women. We found that increased paternal investment in child care and housework remarkably enhanced women's intention to have a second child, especially among employed women. In addition, although family members provide a low percentage of child care in South Korea, such help is likely to be a useful resource for second childbirth among employed women. Somewhat expectedly, older age and longer time since first birth had negative effects on women's second-child intention. There is growing evidence that, in the lowest fertility societies, paternal investment may be an essential resource for promoting future reproductive behavior of women, especially employed women.     

Polygyny and fertility in Morocco: the effect of marital instability

This paper analyses the relationship between polygyny and female fertility in the province of Marrakech (Morocco) taking into account the effect of the previous marital instability (number of marriages) and the possible association between female sterility and type of marriage. In the analysed population, polygyny increases in the small towns. Polygynously married women have a higher level of education and show a higher percentage of use of contraceptive methods than the monogamously married ones. Although polygynously married women initially show lower fertility, multivariate analysis carried out on the group of women between 35 and 49 years old show that there are no significant differences in fertility between monogamously and polygynously married women when the effect of the previous marital instability is considerer. Female sterility does not determine marital instability, although it does determine a significant increase in polygynous marriages among the women without children.     

Fish communities in two environmentally different estuarine systems of Mexico

Mexico has two main types of coasts, an Amero-trailing-edge coast along the Gulf of Mexico and a collision coast along the Pacific, each of which determine the characteristics of their coastal lagoons. The lagoons along the Gulf of Mexico are extensive, tropical and rich in seagrass beds and mangroves, and among these Laguna Madre has 84 species of fishes. In contrast, the lagoons along the Pacific are small, closed, mostly oligohaline and usually lack seagrass beds, and among these Laguna Salinas del Padre has 19 species of fishes. This marked difference in species richness, in turn, has a direct effect on the size and value of the fisheries, as these are regional in the first case and local and seasonal in the second.     

Racial fertility differences: The role of female employment and education in wanted and unwanted childbearing

Abstract

This paper employs data from a merged sample of the National Surveys of Family Growth to examine how female employment status conditions the relationship between education and wanted and unwanted births among African American and white women. A rationale is presented for why a minority group status hypothesis that posits lower fertility among more highly educated African American women as compared to similar white women might find support in the case of wanted births and among certain women, including earlier birth cohorts. Our results provide some evidence for these ideas as well as evidence for a social characteristics hypothesis that predicts convergence of childbearing with rising education. However, persistently higher levels of unwanted births among African American women of all educational levels suggest that the dynamics of racial fertility differences are more complex than either of the hypotheses imply.     

Rural-urban differentials in marital fertility in four Muslim populations

An analysis based on data collected as a part of the World Fertility Survey program in 4 Muslim populations Bangladesh, Java, Jordan and Pakistan does not show a consistent pattern in rural-urban differentials in marital fertility. While no significant diiferential in current fertility by place of current residence is noticeable in Bangladesh and Pakistan, urban women in Jordan showed lower fertility than their rural counterparts. Cumulative fertility, when controlled for duration of marriage, was found to be higher in urban than in rural areas of Bangladesh and Pakistan, but no clear pattern emerged in Jordan. In Java, both current and cumulative fertility were higher in urban than in rural areas; urban women who had spent their childhood and were brought up in the urban environment showed, in most instances, higher fertility than the other residence groups. (author's modified     

The influence of female education,labor force participation,and age at marriage on fertility behavior in Bangladesh

Abstract

This paper studies the relationship between three aspects of female status (education, work experience, and age at marriage) and the use of contraception and fertility in Bangladesh. Education is found to be the variable most strongly correlated with use of contraception and is also one of the significant variables explaining fertility behavior. The most important factor explaining fertility behavior is age at marriage. The higher the age at marriage, the lower the fertility, when all other factors are held constant. Work experience has very little or no effect on current use of contraception and fertility.     

Selection for fertility in mice using different methods of litter size manipulation

Summary A short-term selection experiment for increasing the first-day litter size (LS1) and 28-day litter weight (LW28) was conducted with three populations of mice over 8 generations. Different methods of litter size manipulation were used for the populations — in S the litter size was standardized to 8 (4 , 4 ) on the first day, in LA it was adjusted to the average size of all litters born on the same day and NL had the natural litter size. To eliminate temporary environmental effects, a control population was kept in each case. The selection results per generation were, for LS 1 b=0.30 (S, NL) and 0.20 (LA), and for LW28 b=5.62 g (S), 5.26 g (NL), and 4.32 g (LA). The heritability obtained was between 0.18 and 0.13 for LS 1 and from 0.42 to 0.12 for LW28. The populations differed in the correlated responses for body weight parameters (litter weight gain). The implantation rate increased in populations S and NL (b=0.19, 0.37), but not in population LA. Postnatal mortality went down (b=-0.07) and the dam's milk production rose (b=1.11 g) only in population LA. The estimated partial regression coefficient linking body weight at mating (BWM) for the dam and the daughter's litter size showed an effect on the litter size.     

The effect of claw size and wave rate on female choice in a fiddler crab

How do females select a mate when they have mating preferences for multiple male traits? In experimental studies, female fiddler crabs (Uca mjoebergi) show a strong preference for males with larger claws and higher wave rates. In the field, there is no correlation between male claw size and observed wave rate. Here we document natural mating behaviour and show that females approach males who wave at a higher rate than nearby competitors. On average, an approached male had a significantly larger claw than his two nearest neighbours but did not differ in size from his two closest waving competitors. In general, smaller males were less likely to wave at approaching females. Females therefore approached mates based directly on wave rate but, because smaller males were less likely to wave, this indirectly resulted in female choice for larger than average males. Our study raises two issues. First, how do we relate the field results to previous experimental studies showing a female preference for larger claws? Second, in U. mjoebergi, males defend smaller neighbours against intruders. Our study suggests that one benefit of such defence coalitions is to decrease the number of immediate competitors present during female mate choice by retaining smaller neighbours.     

不同土壤类型和肥力玉米地土壤养分根际效应研究

采集吉林省玉米植株及土壤样品,研究不同土壤类型和肥力,玉米不同品种和生育时期土壤－植物系统根际养分动态变化及植物吸收的相互关系,结果表明,玉米地土壤ＮＨ＾＋４－Ｎ、ＮＯ＾－３－Ｎ在根际富集,其变化主要与化肥供应有关,高肥力土壤根际有效磷亏缺,种植密度越大,根际亏缺率超大;低肥力土壤则有效磷在根际略高。高肥力土壤有效钾较高,根际有效钾富集也更明显,茎叶、根对养分的吸收量顺序为：Ｎ     

Lack of effect of nicotine on the fertility of male and female mice

Summary Nicotine, administered by sub-cutaneous injection over a period of six weeks, was found to be ineffective in breaking male mouse chromosomes as judged by dominant lethal tests. In addition, no indication of an effect of nicotine on the fertility of female mice, or on the development of the foetusin utero, was found.     

Otolith size trends in marine fish communities from different depth strata

A comparison of 681 saccular otoliths (sagitta) from 134 species belonging to six demersal communities from different depth strata and the epipelagic community from the north-western Mediterranean Sea was made in order to study otolith relative size and function related morphologies. A relationship between otolith size composition, habitat and depth was found. The epipelagic community was characterized by species with very small and small otolith sizes (68% of the epipelagic species). In the demersal communities, the proportion of species with large sagitta increased with depth until 750 m (reached 50% of the species of the upper slope). The abyssal community (between 1000 and 2000 m), however, was characterized by a decrease in the mean otolith size and an increase in the proportion of species with very small otoliths. With exception of the abyssal community, endogenous causes (a mixture of geneaology, plesiomorph characters shared by the all species of the taxonomic group and recent adaptive ones) may be even more important than exogenous factors in determining the otolith relative size. Within the endogenous causes that condition sagitta size, the adaptive features associated with specialization in acoustic communication are relevant.     

Tropical forest communities in southeastern Mexico

A phytosociological study was carried out along a 450 kmtransect in tropical southeastern Mexico in order to identify plantcommunities.Five major plant communities were distinguished and described:Those communities reflect preference of different environmentalfactorssuch as soils, precipitation and local relief. Further, the major threats(hurricanes, fires, agriculture) to the vegetation of the study areaare discussed.     

High fertility of Old Colony Mennonites in Mexico

Old Colony Mennonites in Mexico appear to demonstrate natural fertility, using no form of artificial birth control and apparently not attempting to limit family size. The resulting fertility is nearly as high as that of the Hutterites, although the Mennonites lack the communal economic system of the latter. Most Mennonites in Mexico migrated from Canada in the 1920s, and the largest single settlement, called the Manitoba Colony, is one of four in the state of Chihuahua. A 1967 partial census obtained data from 38% of the Mennonite households. Family size in the sample was close to that in a local survey taken in the same year. Available church records matched with census forms permitted verification of and corrections to 560 female reproductive histories. The median number of live births to women over age 45 years was 9.5, compared with 10.4 in the Hutterites. Age-specific marital fertility rates and birth intervals closely resembled those of the Hutterites.     

不同石油浓度对浮游细菌群落影响的新发现

【目的】研究不同浓度石油污染对海水中浮游细菌群落结构及多样性的影响,并尝试阐述造成这种影响的机理。【方法】将采集自海上钻井平台附近的表层海水样品,在实验室条件下用不同浓度的石油(0?10 g/L)处理1周后,用末端限制性片段长度多态性(TRFLP)方法检测其细菌群落结构及多样性变化情况。【结果】得到了一些与以往研究结果不同的新发现,如细菌多样性不是简单地随石油浓度的升高而降低,而是呈现先降低再升高最后又降低的趋势。0.1 g/L石油处理组(M0.1)与0.5 g/L处理组(M0.5)、2.5 g/L石油处理组(M2.5)和10 g/L处理组(M10)的细菌群落结构更相似,且添加石油处理组(M0.1、M0.5、M2.5、M10)与未添加石油的对照组(M0)间细菌群落结构相差较大。与石油降解相关的细菌主要集中于变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes)。基于TRFs在不同处理组的相对比例,可将实验得到的52个TRFs划分为6种类型：低浓度(I)、中浓度(II)、高浓度(III)、广浓度(IV)、窄浓度(V)石油适应型和石油敏感型(VI)细菌。另外,首次提出“碳(能)源-毒素”假说来解释石油污染对浮游细菌群落的影响。【结论】石油污染对浮游细菌群落的影响与石油的浓度和海水中原有的历史细菌群落密切相关,可以按照浮游细菌对石油的适应性对其进行分类,并且“碳(能)源-毒素”假说能较好地解释石油污染对浮游细菌群落的影响。     

The effects of different insemination regimes on fertility in mares

This study investigated the effects of different artificial insemination (AI) regimes on the pregnancy rate in mares inseminated with either cooled or frozen-thawed semen. In essence, the influence of three different factors on fertility was examined; namely the number of inseminations per oestrus, the time interval between inseminations within an oestrus, and the proximity of insemination to ovulation. In the first experiment, 401 warmblood mares were inseminated one to three times in an oestrus with either cooled (500 x 10(6) progressively motile spermatozoa, stored at +5 degrees C for 2-4 h) or frozen-thawed (800 x 10(6) spermatozoa, of which > or =35% were progressively motile post-thaw) semen from fertile Hanoverian stallions, beginning -24, -12, 0, 12, 24 or 36 h after human chorionic gonadotrophin (hCG) administration. Mares were injected intravenously with 1500 IU hCG when they were in oestrus and had a pre-ovulatory follicle > or =40mm in diameter. Experiment 2 was a retrospective analysis of the breeding records of 2,637 mares inseminated in a total of 5,305 oestrous cycles during the 1999 breeding season. In Experiment 1, follicle development was monitored by transrectal ultrasonographic examination of the ovaries every 12 h until ovulation, and pregnancy detection was performed sonographically 16-18 days after ovulation. In Experiment 2, insemination data were analysed with respect to the number of live foals registered the following year. In Experiment 1, ovulation occurred within 48 h of hCG administration in 97.5% (391/401) of mares and the interval between hCG treatment and ovulation was significantly shorter in the second half of the breeding season (May-July) than in the first (March-April, P< or =0.05). Mares inseminated with cooled stallion semen once during an oestrus had pregnancy rates comparable to those attained in mares inseminated on two (48/85, 56.5%) or three (20/28, 71.4%) occasions at 24 h intervals, as long as insemination was performed between 24 h before and 12 h after ovulation (78/140, 55.7%). Similarly, a single frozen-thawed semen insemination between 12 h before (31/75, 41.3%) and 12 h after (24/48, 50%) ovulation produced similar pregnancy rates to those attained when mares were inseminated either two (31/62, 50%) or three (3/9, 33.3%) times at 24 h intervals.In the retrospective study (Experiment 2), mares inseminated with cooled semen only once per cycle had significantly lower per cycle foaling rates (507/1622, 31.2%) than mares inseminated two (791/1905, 41.5%), three (464/1064, 43.6%) or > or =4 times (314/714, 43.9%) in an oestrus (P< or =0.001). In addition, there was a tendency for per cycle foaling rates to increase when mares were inseminated daily (619/1374, 45.5%) rather than every other day (836/2004, 42.1%, P = 0.054) until ovulation.It is concluded that under conditions of frequent veterinary examination, a single insemination per cycle produces pregnancy rates as good as multiple insemination, as long as it is performed between 24 h before and 12 h after AI for cooled semen, or 12 h before and 12 h after AI for frozen-thawed semen. If frequent scanning is not possible, fertility appears to be optimised by repeating AI on a daily basis.     

The effect of different initial size distributions on the growth of Atlantic halibut

Growth rate of individually tagged medium–sized (249±6·9 g) juvenile halibut was 18% lower when medium sized fish were reared alone (treatment Mm) as compared with rearing with either large/dominant (382±12·1 g) (Ml) or small/subordinate (158±3·1 g) (Ms) conspecifics. The coefficient of variation of weight of medium–sized fish increased with weight in both the Mm and the Ml group whereas it was stable in the Ms group. Size rank correlation between initial and final weight was highest in the Mm group and lowest in Ms. A negative rank correlation was found also between initial weight and overall growth rate for the Ms treatment groups but not the other groups. It is hypothesized that interactions between similar–sized individuals in the Mm treatment group had an inhibiting effect on growth as social hierarchies were being resolved.