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"This note gives the conditions under which there is an interior optimum rate of population growth in a two-generations-overlapping model. These conditions imply complementarity both in production and in consumption. They also validate Samuelson's serendipity theorem."
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New information on maximal possible potential selection and its component values in some ethno-territorial groups in CIS was presented. The heterogeneity observed in the Crow's index and its components can be explained as a result of the differences in the social economic status of the groups studied and the influence of climate geographical factors. The data gathered during the biodemographical study of 67 populations allowed to detect regularities of the effects of selective factors in world population: non-random and discrete nature of considered populations distribution in the coordinate space of selection components associated with differential mortality (I) and differential fertility (I) was shown. Differentiation of three big aggregations of populations was shown: urbanized contemporary communities with low I values; small endogamous populations, mostly of hunters and gatherers; small towns' populations and rural populations with balanced reproductive indices. Microevolutionary changes take place in the latter conglomerate even now, statistically subdividing it into two clusters. A proposition was made about the existence of "ecological optimum" for populations intermediate between advanced industrial communities and communities of hunters and gatherers, corresponding to the population size and the nature and rate of population reproduction.
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"In this paper, I examine the implications of the Rawlsian maximin criterion for optimal population size and intergenerational allocation of resource when fertility is endogenous. I show that whenever children are better-off than their parents in laissez-faire, then the size of the population and parental bequests are also optimal according to the Rawlsian criterion....I then show that by using proper price-based corrective policies, society can achieve a Rawlsian optimal allocation."
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Thermal acclimation by Saxifraga cernua to low temperatures results in a change in the optimum temperature for gross photosynthetic activity and may directly involve the photosynthetic apparatus. In order to test this hypothesis photosynthetic electron transport activity of S. cernua thylakoids acclimated to growth temperatures of 20 degrees C and 10 degrees C was measured in vitro. Both populations exhibited optimum temperatures for whole chain and PSII electron transport activity at temperatures close to those at which the plants were grown. Chlorophyll a fluorescence transients from 10 degrees C-acclimated leaves showed higher rates in the rise and subsequent quenching of variable fluorescence at low measuring temperatures; 20 degrees C-acclimated leaves showed higher rates of fluorescence rise at higher measuring temperatures. At these higher temperatures, fluorescence quenching rates were similar in both populations. The kinetics of State 1-State 2 transitions in 20 degrees C- and 10 degrees C-acclimated leaf discs were measured as changes in the magnitude of the fluorescence emission maxima measured at 77K. Leaves acclimated at 10 degrees C showed a larger F730/F695 ratio at low temperatures, while at higher temperatures, 20 degrees C-acclimated leaves showed a higher F730/F695 ratio after the establishment of State 2. High incubation temperatures also resulted in a decrease in the F695/F685 ratio for 10 degrees C-acclimated leaves, suggesting a reduction in the excitation transfer from the light-harvesting complex of photosystem II to photosystem II reaction centers. The relative amounts of chlorophyll-protein complexes and thylakoid polypeptides separated electro-phoretically were similar for both 20 degrees C- and 10 degrees C-acclimated leaves. Thus, photosynthetic acclimation to low temperatures by S. cernua is correlated with an increase in photosynthetic electron transport activity but does not appear to be accompanied by major structural changes or different relative amounts in thylakoid protein composition.