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No description available.

The study investigates and interprets the factors that contributed to the recent decline in fertility in Sri Lanka, despite its low economic standing. It seeks to elucidate the social transformation that has taken place and looks at the socio-cultural determinants that have brought about the process of fertility transition. In this regard, the significant effects of the welfare measures in force in the country in respect of health, education, nutrition and housing have been brought to light. Hence the study tends to fall outside the scope of the conventional wisdom laid down in the demographic transition theory outlined by Notestein, which emphasised the contribution that economic development plays in lowering fertility. The approach to the study hinges on selected variables like education, age at marriage, gender roles per se and female employment. The cardinal role played by free education in contributing to the transition is given particular coverage. Education is treated more as a cultural asset which determines and shapes values, preferences and aspirations in respect of marriage, fertility, family formation and other aspects such as career development which enables women to play roles away from home. Unfortunately, inferences about women's position do not always gain statistical support, as they are intricately woven into the fabric of societal gender settings and traditions. In respect of age at marriage, the socio-cultural factors of society like the caste system, a dowry and horoscope matching with details of Karmic determinants have been examined in some detail. The study also uncovers the social deprivation aspects which for long led women in the plantation sector to experience fertility performance lower than the national level. Going by normal demographic rationale, their high degree of labour force participation should account for it. But it was social deprivation and the resultant low nutritional levels that reduced their reproductive ability to low levels. With a better life ushered in by a programme of social uplift during the early 'eighties, this ethnic group showed signs of first a rise in fertility, and on having reached the threshold it has now begun showing signs of a decline attributable to healthier lives. Similarly, a relatively invisible agent, the prevalent “urban outlook," is shown to contribute to the transition process, and has recently become even more significant due to the intensive rural amelioration efforts of the government. This outlook is all pervasive and permeates the society in general in effecting the transition under review.

Dunlin from two breeding populations, C.a.schinzii from Iceland and C.a.alpina from northern Scandinavia, were studied during and after migration through Teesmouth, north-east England, and in captivity. C.a.schinzii winters in north-west Africa and has a much longer migration pathway than C.a.alpina which winters in Britain and around the North Sea. Measurements of Resting metabolic Rate (RMR) were made for the two subspecies of Dunlin in March and November in order to establish the relationship between resting metabolic rate and temperature and hence energy costs of living at different temperatures (20 C - 0 C). Energy costs of living in C.a.alpina were 21% higher than C.a.schinzii. Measurements of Basal Metabolic Rate (BMR) were made for the two subspecies (before, during and after moult) in conjunction with measurements of body compositions using Total Body Electrical Conductivity (TOBEC) in order to estimate the costs of moult. Energy costs of moult were 1692 KJ for alpina and 1016 KJ for schinzii.Energy costs of migration were estimated by measuring the amount of fat laid down before departure by wild Dunlin of the two populations, with the aid of Total Body Electrical Conductivity (TOBEC). Energy costs of migration were estimated as 3489 KJ for alpina, and 5156 KJ for schinzii. Energy costs of egg production and incubation were estimated from other workers’ studies of other (similar) species. Energy costs of egg production were only 220 KJ for the two subspecies whereas the costs of incubation were 1232 KJ and 1143 KJ in alpine and schinzii, respectively. In contrast to the suggestion by Drent and Piersma (1990), I have found that the costs of migration are considerably less than the costs of living. Also the total annual energy cost for those Dunlin wintering in colder areas i.e. C.a.alpina is much higher than for those wintering in tropical regions i.e. C.a.schinzii. Energy costs are not the only factors that affect a bird's lifetime output of young. C.a.alpina uses a different migration strategy to C.a.schinzii but may breed on better breeding grounds, and hence achieve more successful reproduction.

Patterns and processes of post-war Tunisian migration are examined in this thesis from a spatial perspective The concept of 'migration regions' proved particularly interesting in this context, highlighting the orderly character of internal migration Comparison of different taxonomic procedures for transforming interaction matrices not only illustrated the advantages and disadvantages of different clustering techniques, but also facilitated explanation of contemporary migration patterns The hypothesis of the 'mobility transition' provides an interesting yardstick against which trends in internal migration and other mobility characteristics may be measured Although the development of Tunisian migration resembles in some respects the pattern prescribed by the mobility transition hypothesis, it IS shown that it would be wrong to conclude that the evolution of Tunisian migration is a predetermined unilinear process International migration grew rapidly in importance to Tunisian job seekers in the late 1960s and early 1970s, becoming more important in some regions of Tunisia than out-migration to Tunis. Calculation of migration quotients for emigration to France and Libya shows that international movement of workers has been a highly selective process, not only with regard to migrant characteristics, but also with regard to regions of origin and destination An attempt is made to explain the changing pattern of Tunisian emigration, and to identify elements of spatial order within the evolving emigration process migration both at the internal and international scale is closely associated with migrants aspirations for occupational and social mobility. An understanding of the complex relationships between these different forms of mobility is a prerequisite to meaningful migration planning. The thesis concludes by out ling the relevance to policy formulation of spatial analysis of migration and employment which the Tunisian government might adopt for migration and manpower planning,

The problem of the relationship between population and food supply in Menoufiya is a small scale example of that facing the whole of Egypt. The main problem is not as a result of insufficient production of food from the land, but as a result of continuously increasing population with high density which causes pressure on the limited cultivated land. It is important to understand the population characteristics of Menoufiya, which are even distribution of high density; high fertility; a high proportion working in agricultural activities; a majority of young people; and high illiteracy especially among females and farmers. One response to increasing population has been heavy out-migration to the large cities of Egypt. Despite the fact that Menoufiya is facing a great problem in increasing food production caused by decreasing acreage of land; frag mentation of farms; disguised unemployment; limited machinery and increased landless, the region is one of the main agricultural regions in Egypt. It is characterized by one of the highest productivities for food among the governorates of Egypt, because of the excellent environmental conditions - fertile soils with flat surface, abundant water of good quality from the Nile and its canals, and warm temperatures which permit year-round plant growth and the intensive system of farming. The main food crops in the region are maize, wheat, broad and soya beans covering about 50 per cent of the total cropped area. Vegetables are grown all the year-round, especially potatoes, tomatoes and beans. In addition, the region is one of the main producers of : fruit such as citrus, grapes and bananas. There is a large area cultivated with clover as a fodder for animals in winter, but animal feed is in chronic short supply especially in summer. The study of food production in Menoufiya shows that it is abundant and increasing, being able to feed the dense population of the region as well as some of these in major urban centres especially Greater Cairo in most vegetables, fruit, and animal products. In fact, there is no shortage of the majority of foodstuffs (except for wheat) in the region at the present time, but the problem may become more acute in the future as the population will increase more rapidly than food production. The solution of the problem of population and food resources in Menoufiya - as well as in Egypt - must be sought both in accelerating the development of agricultural processes and in slowing down the growth of population through social and economic development. Such development is not in isolation, for Menoufiya provides migrants to Egypt's large cities and to some other Middle Eastern countries. So the problem is not just one of a man-land ratio, but of population in relation to total available resources.

The aim of this study was to examine the Zoroastrians of Yazd, Kerman and Tehran to determine whether or not they differed from each other genetically and from the host population of Iran; to study the Parsis and Iranis - Zoroastrians Who had migrated to India in the 7th Century A.D., and compare the results with those of neighbouring Indian populations. It was hoped to obtain a large number of samples in order to make accurate comparisons, but, owing to the contemporary complex political situation, this proved impossible. Attempts were made to explain the variants in terms of present day demo graphic theories but were hampered by the paucity of published data. Blood, serum and isoenzyme group examinations were made. Serological and electro0ioretic techniques were used to determine ABo, MNSs, Rh, Kell, Duffy, KP, haptoglobin, adenylate kinase, acid fiiosphatase, esterase D and 0ios0ioglucanutase factors in a total of 469 Zoroastrians. Demographic features of contemporary Zoroastrians were studied and the results compared with those of Iranians and Parsis. (No demographic data was available for the Iranis of India.) This revealed that the fertility ratio of the Zoroastrians is lower and present day infant mortality higher than those for the latter groups. Serological test results together with the demographic findings suggest that the long practise of consanquinial marriage may account for the differences which we can observe today.

No description available.

Extensive community-based sampling and single-species genetic analysis were used to study factors driving stream invertebrate community assembly on islands. Macroinvertebrates and physicochemistry were surveyed in forty-two streams on La Palma, La Gomera, Tenerife and Madeira (Macaronesia). Island faunal relationships and the role of the stream and catchment environment in determining community composition were investigated with multivariate analyses; assemblage nestedness and species richness, occupancy and abundance were also examined. The relationship between genetic differentiation and range size was tested using allozyme variation in selected species. Island species pools differed in community composition and species richness (total, and endemic), broadly as predicted by theory of island biogeography. Stream and island species richness were correlated, showing unsaturated, possibly dispersal-limited, communities, and stream faunas were nested, evidence that assemblages were not random (e.g. only generalist/dispersive taxa occur at species-poor sites). Endemics occurred in more streams than non-endemics, suggesting greater habitat availability for the former, but similar niche width, endemic and non-endemics having similar local abundance. Species richness, community composition and the abundances of individual species were correlated with stream physicochemistry, itself reflecting geology, rainfall, altitudinal zonation of vegetation and the intensity of stream exploitation. Allozyme variation was surveyed in Mesophylax aspersus (Trichoptera: Limnephilidae) and Wormaldia tagananana (Trichoptera: Philopotamidae), respectively having widespread and localised distributions. Population structure supported the hypothesis that range size is, at least partly, limited by poor dispersal ability in W tagananana. Genetic variation in Ancylus striatus (Gastropoda: Ancylidae) was typical of polyploidy and selffertilisation/ parthenogenesis. Breeding system has consequences for a species' colonisation ability, and may partially explain the wide distribution of A. striatus within the islands. Variation in community composition reflected patterns at a range of scales. Biogeography detennined the island species pooL whilst local physicochemistry determined richness and community composition within islands. Species characteristics that affect their colonisation and c:\tinction probabilities (e.g. habitat selection at the local- and mesoscaks, dispersal patterns and breeding system). influence hoth the local and regional species pools.

The purpose of this thesis is to present a different approach to the formulation of differential equation mathematical models for interacting populations. It does this through considering a geometric method. The solution to the differential equations are forced, through theuformulation, to lie on the surface of well known three-dimensional shapes. It is this that allows detailed analysis of how, and why, the solution of the equations behave as they do. The thesis firstly reviews some of the skills and techniques used in the formulation and alysis of differential equation models to give a background for some of the analysis used the geometric approach to modelling. The geometrical approach is then presented using two three-dimensional surfaces, the ellipsoid and the torus. Also examined is an extension of the basic shape to higher dimensions. Using the three-dimensional shape as a reference, a four-dimensional representation is formulated. This increase in the number of variables in the model allows more situations to be modelled. The thesis concludes by discussing the use of the type of model produced by the geometric approach by addressing some of the advantages and disadvantages of this approach. It ends with some extensions to this study of geometric models for future work.