Search results for "SEXUAL DIMORPHISM"
showing 10 items of 154 documents
AN ANALYSIS OF CONTINENT-WIDE PATTERNS OF SEXUAL SELECTION IN A PASSERINE BIRD
2006
Patterns of selection are widely believed to differ geographically, causing adaptation to local environmental conditions. However, few studies have investigated patterns of phenotypic selection across large spatial scales. We quantified the intensity of selection on morphology in a monogamous passerine bird, the barn swallow Hirundo rustica, using 6495 adults from 22 populations distributed across Europe and North Africa. According to the classical Darwin-Fisher mechanism of sexual selection in monogamous species, two important components of fitness due to sexual selection are the advantages that the most attractive males acquire by starting to breed early and their high annual fecundity. W…
A test of male mating and hunting success in the kestrel: the advantages of smallness?
1996
We tested female choice for male wing and tarsus length and body mass in the kestrel (Falco tinnunculus), a species in which males average about 10% smaller than females. We also studied how male characters are related to their hunting success. In the laboratory, females preferred lighter males with shorter tarsi as mates, if the difference in those characters between competing males was larger than average. Lighter and shorter-winged males seemed to be better hunters than heavier and longer-winged males. Field observations in a year in which voles were scarce suggested that shorter-winged males were also better food providers in courtship feeding than longer-winged males,although in good v…
Effects of azadirachtin on reproduction and egg development of the heteropteranOncopeltus fasciatusDallas
1986
Azadirachtin injected into newly hatched adults of Oncopeltus fasciatus affected longevity, fecundity and hatchability of eggs from treated parents. There were marked differences between males and females. Whereas mortality was higher in females, reproduction was interrupted at lower doses in males: 0.125 μg caused impotency. Topical treatment of normal eggs had no demonstrable effect on egg hatch. The studies showed that in respect to a possible use of azadirachtin in insect pest managment, the interruption of reproduction and adult development is of no less importance then growth interruption in larvae (Dorn et al. 1986). Zusammenfassung Die Wirkung von Azadirachtin auf Reproduktion und E…
Sex ratio and spatial distribution of male and female Antennaria dioica (Asteraceae) plants
2011
Sex ratio, sex spatial distribution and sexual dimorphism in reproduction and arbuscular mycorrhizal colonisation were investigated in the dioecious clonal plant Antennaria dioica (Asteraceae). Plants were monitored for five consecutive years in six study plots in Oulanka, northern Finland. Sex ratio, spatial distribution of sexes, flowering frequency, number of floral shoots and the number and weight of inflorescences were recorded. In addition, intensity of mycorrhizal fungi in the roots was assessed. Both sexes flowered each year with a similar frequency, but the overall genet sex ratio was strongly female-biased. The bivariate Ripley’s analysis of the sex distribution showed that within…
Relationships Between Dimorphism, Cell Wall Structure, and Surface Activities in Candida albicans
1991
Most cells are covered with a complex network of interacting molecules that form the extracellular matrix. These molecules (proteins and polysaccharides) are secreted locally and interact among themselves to form an organized structure outside the cell plasma membrane. In unicellular eukaryotic organisms and plant cells, this structure is reinforced to withstand osmotic changes in the external environment, giving rise to the so-called cell wall.
INSEGNARE AL MASCHILE E AL FEMMINILE SECONDO GIUSEPPE MARI
2021
La riflessione storica e quella teoretica di Mari sul dimorfismo sessuale, che è presente in tutte le culture, costituiscono la base per giustificare la differenziazione parziale dell’educazione del ragazzo e della ragazza, considerando i ruoli che essi svolgeranno, l’uno di padre e l’altra di madre: una paternità e una maternità che vanno ben oltre la generatività fisica. Mari ha collocato la didattica di genere all’interno del sistema pedagogico dell’educazione personalizzata. The historical and Mari's theoretical reflection on sexual dimorphism that exists in all cultures form the basis for justifying the partial differentiation in boy and girl education, considering the roles they will …
A Cross-sectional Growth Study of Forearm Length and Tibial Length in an Indigenous Andean Population of 6 to 19 Years of Age.
1997
Patterns of growth in forearm length and tibial length were studied in 149 school-children of Aymara ancestry (73 boys and 76 girls), aged 6 to 19 years. The investigation was based on a cross-sectional survey performed in 1987 in the rural community of Putre (3, 530 m), northern Chile. The results show that there is little sexual dimorphism over the age period of 6 to 13 years, while sex differences are more pronounced between the ages of 14 and 17 years, both for forearm length and tibial length, with boys having higher means. Correspondingly, the maximum values achieved for both measurements are greater in boys than in girls. The growth spurt begins about two years earlier in girls than …
Breeding strategy and morphological characters in an urban population of blackbirds, Turdus merula
2001
Pairing patterns in monogamous birds are thought to be the consequence of mutual mate choice by males and females for characters linked to individual quality in the opposite sex. Although this may result in assortative pairing for a single character, there may be no simple match between male and female phenotype if the traits linked to individual quality are sex specific. For instance, in several passerine species, females tend to select males on the basis of territory quality or characters that may reflect health or vigour, whereas males benefit from pairing with females in good condition that breed early because early breeding increases reproductive success. We investigated pairing patter…
Tooth size discrepancy in a Libyan population, a cross-sectional study in schoolchildren
2014
Objetives: The aim of this cross-sectional study was to investigate the tooth size discrepancy (TSD) in a group of Libyan schoolchildren, and to compare TSD between sexes. Material and Methods: The sample comprised 333 Libyan schoolchildren (162 males with a mean (SD) age of 14.4 (1.1) years, and 171 females with a mean age of 14.1 (1.1) years). Anterior and overall TSD ratios were computed using descriptive statistics. Sex differences were statistically assessed using an independent t-test ( P 0.05). The percentages of participants showing more than 2 SD variation for the anterior and overall ratios comprised 3% and 4.2% of the total sample, respectively. Conclusions: The anterior and over…
Geranium sylvaticum increases pollination probability by sexually dimorphic flowers
2022
Sexual dimorphism is expressed as different morphologies between the sexes of a species. Dimorphism is pronounced in gynodioecious populations which consist of female and hermaphrodite individuals. The small size of female flowers in gynodioecious species is often explained by resource re-allocation to seed production instead of large flowers. However, pollinator attraction is critical to female fitness, and factors other than resource savings are needed to explain the small size of female flowers. We hypothesized that the floral size dimorphism in the perennial gynodioecious Geranium sylvaticum (L.) is adaptive in terms of pollination. To test this “pollination hypothesis,” we video record…