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At least 19 recordsLinked to original sources
PubMed1976

Anthropological perspectives on population growth.

Rapid population growth affects many different system levels simultaneously: the individual, the family, the community, the nation-state and the world. What may appear to be an optimal population level for one system, given certain value premises, may not be optimal for another. Anthropologists can contribute to an understanding of rapid growth by generating an appreciation for the complexity of the phenomenon, and by providing representation for a range of cultural viewpoints. This may help to reduce the risk we now run of committing all of mankind to a singular path which may prove to be an evolutionary dead end.

Crowding↗
PubMed1979

Patterns of suburban population growth, 1970--75.

Population redistribution within U.S. suburban rings between 1970 and 1975 was characterized by frequent population declines for individual suburbs. On the whole, recent spatial patterns of suburban population decline are similar in nature, if not overall levels, to those found in the 1950s and 1960s. Population decline is greatest in the inner suburbs, and is also evident, to some extent, in the most peripheral suburbs. Patterns for all metropolitan areas mask clear variation among metropolitan areas. This variation is related to metropolitan age or historical period of development.

Employment↗
PubMed1978

The malaria burden and population growth in the Solomon Islands.

This paper outlines the result of the control of infectious diseases, and more especially malaria, on the growth of populations in the Solomon Islands since 1931, the year of the first census, to 1976, the year in which the fourth census revealed, that a population explosion had occurred, and was occurring unabated.

Adolescent↗
PubMed1975

Comparison of logistic equations for population growth.

Two different forms of the logistic equation for population growth appear in the ecological literature. In the form of the logistic equation that appears in recent ecology textbooks the parameters are the instantaneous rate of natural increase per individual and the carrying capacity of the environment. In the form of the logistic equation that appears in some older literature the parameters are the instantaneous birth rate per individual and the carrying capacity. The decision whether to use one form or the other depends on which form of the equation is biologically more realistic. In this study the form of the logistic equation in which the instantaneous birth rate per individual is a parameter is shown to be more realistic in terms of the birth and death processes of population growth. Application of the logistic equation to calculate yield from an exploited fish population also shows that the parameters must be the instantaneous birth rate per individual and the carrying capacity.

Mathematics↗
PubMed1992

Population growth makes waves in the distribution of pairwise genetic differences.

Episodes of population growth and decline leave characteristic signatures in the distribution of nucleotide (or restriction) site differences between pairs of individuals. These signatures appear in histograms showing the relative frequencies of pairs of individuals who differ by i sites, where i = 0, 1, .... In this distribution an episode of growth generates a wave that travels to the right, traversing 1 unit of the horizontal axis in each 1/2u generations, where u is the mutation rate. The smaller the initial population, the steeper will be the leading face of the wave. The larger the increase in population size, the smaller will be the distribution's vertical intercept. The implications of continued exponential growth are indistinguishable from those of a sudden burst of population growth Bottlenecks in population size also generate waves similar to those produced by a sudden expansion, but with elevated uppertail probabilities. Reductions in population size initially generate L-shaped distributions with high probability of identity, but these converge rapidly to a new equilibrium. In equilibrium populations the theoretical curves are free of waves. However, computer simulations of such populations generate empirical distributions with many peaks and little resemblance to the theory. On the other hand, agreement is better in the transient (nonequilibrium) case, where simulated empirical distributions typically exhibit waves very similar to those predicted by theory. Thus, waves in empirical distributions may be rich in information about the history of population dynamics.

Biological Evolution↗
PubMed1975

The containment of world population growth.

The world has reached the present position of unprecedentedly rapid population growth not by achieving uniquely high fertility but by bringing about extraordinarily low mortality. The high growth rate and the built-in momentum of the age structure are obstacles to achievement of an acceptable standard of living for most of the world's population. Although government population programs have the potential to curb this growth rate, this potential has not been realized, and such programs are too often perceived both by their administrators and the population concerned as an end in themselves rather than a means toward a better standard of living. It is in this latter perspective, and in the context of the total development process, that population programs should be implemented.

Adult↗
PubMed1978

The momentum of population growth with time dependent net maternity function.

The momentum of population growth problem of Keyfitz is generalized to contain a gradual change of the age-specific birth rate ro the level of bare replacement. Assuming a time dependence for the net maternity function of the form (formula: see text) R being the net reproductive rate, we show that for the Malthusian model the asymptotic birth rate is increased by exp (r/lambda), where r is the rate of increase of the population before t = 0. A numerical method for obtaining the asymptotic birth rate for a general net maternity function with the same time dependence is outlined.

Age Factors↗
PubMed1976

On the stability of the stationary state of a population growth equation with time-lag.

If in the Verhulst equation for population growth the reproduction factor depends on the history then the equilibrium may become unstable and oscillations and even non-constant periodic solutions may occur. It is shown that the equilibrium is unstable if the reproduction factor at time t is, up to a sufficiently large factor, an arbitrary average of the population densities in the interval (t-2, t-1).

Mathematics↗
PubMed1975

Mammary carcinoma cell population growth in preirradiated and unirradiated transplant sites. Viable tumor growth, vascularity, and the tumor-bed effect.

Although preirradiation of the transplant site profoundly depresses growth of subsequently grafted carcinomas, the potential rate of tumor cell population growth was very similar within the viable regions of large and small tumors grafted in preirradiated or unirradiated sites. The vascular space per unit of viable tumor mass has previously been shown to be constant in such viable tumor tissue. It is concluded that the tumor-bed effect is due to suppression of vascular growth capability. Insofar as therapeutic procedures depend on relative functional vascular space, the sensitivity per unit mass of viable tissue would be expected to be very similar in large and small tumors growing in unirradiated or preirradiated sites.

Adenocarcinoma↗
PubMed1978

The effects of zero population growth on the incidence of cleft lip and palate in Western Australia.

A total of 613 cases of cleft lip, cleft palate, and combinations of both (CLP(P)) has been ascertained in the period from 1958 to 1975 in Western Australia. Near-total ascertainment of cases during this period was obtained from multiple sources. There has been a significant decline in the total incidence and the cleft lip and palate (CLP) incidence in males. The hypothesis is presented that these changes are linked to the changing fertility pattern throughout Australia (as technological improvements are made in the simplicity and efficacy of birth control), and abortion (as social attitudes change); and as the birthrate drops towards zero population growth (ZPG). The paper presents two critical observations: (i) the link between CLP(P) incidence, and demographic changes; (ii) in differing behaviour of cleft lip (CL) and CLP, which were previously regarded as linked conditions.

Australia↗
PubMed1979

The limiting effect of host availability for the immature stages on population growth in economically important ixodid ticks.

Of 12 southern African species of ixodid ticks in which the adults are commonly parasitc on cattle, only 4 exhibited massive increases in abundance in the absence of dipping. It is suggested that host availability for the immature stages is the major factor limiting population growth in a given environment. The species showing large increases in abundance are those in which the immature stages are predominantly parasitic on cattle, whereas the species showing small to moderate increases in abundance are those in which the immature stages are parasitic on specific nonungulate hosts.

Animals↗
PubMed1976

Toxicity of polychlorinated biphenyls (PCBs) to Euglena gracilis: cell population growth, carbon fixation, chlorophyll level, oxygen consumption, and protein and nucleic acid synthesis.

Populations of Euglena gracilis in exponential growth under light were exposed to 2.5, 5.0, 7.5, and 10 ppm of Aroclor 1221. The ID50/48 of Aroclor 1221 was estimated to be 4.4 ppm, while Aroclor 1232 tested at 20, 35, 50, and 100 ppm resulted in an id50/48 of 55 ppm. With Aroclor 1242, no inhibition of growth was observed with up to 100 ppm exposure. Cell cultures exposed to 4.4 ppm of Aroclor 1221 for 48 hrs had a significantly reduced rate of carbon fixation and reduced levels of chlorophyll after correction for cell density. Oxygen consumption was not affected at the ID50 level of the Aroclor. Uptake of [3H]-leucine in treated cultures was twice that of controls, and [3H]-uridine uptake was significantly lower. Uptake of [3H]-thymidine, and incorporation of [3H]-leucine, [3H]-thymidine, and [3H]-uridine were not significantly different in treated and control cultures. Thes results suggest that at the ID50 level, polychlorinated biphenyls (PCBs) reduce cell population growth in Euglena gracilis by inhibition of photosynthesis and/or chlorophyll production.

Animals↗