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Biomedical subjects

A S Severtsov

Publications and source records attributed to A S Severtsov.

8 recordsLinked to original sources
PubMed1992

[Dynamics of numerical changes in human population in terms of animal population ecology].

The author uses data concerning the natural regulation of population size and growth among animals to consider possible future scenarios for human population growth. Four possible variants are considered: "numerical stabilization and its consequences connected with density effect; sharp slump caused by a global ecological catastrophe; limited slump brought about by exhaustion of resources and environmental pollution; numerical decrease through birth regulation. It has been shown that only the last variant can, in [the] case of the human population being 1.2-1.5 billion people, ensure restoration of [the] biosphere with keeping [the] existing tempo of scientific-technological progress." (SUMMARY IN ENG)

Demography↗
PubMedDate not supplied

[Comparison of variability of Rana temporaria (Amphibia, Anura) gastrula from different populations developing under the conditions of antropogenic pollution].

The gastrulation of Rana temporaria embryos was studied at the natural spawning sites of Moscow city and Moscow district by means of morphometric analysis. We demonstrated that anthropogenic pollution plays an important role in morphogenesis of Anura. The measurements of embryos from the Moscow ponds made it possible to show an increased variability of gastrulation. Moreover, the level of gastrulation variability depends on the degree of pollution of a spawning pond and is coupled with increased correlations between the morphological features. This increase of correlations could be due to: (1) an increased number of correlating features (appearance of new correlations) and (2) strengthening of the existing correlations. The first way makes the gastrulation process more coordinated, and the second one causes the appearance of morphological structures, which are normally formed only at the next developmental stages.

Adaptation, Physiological↗
PubMedDate not supplied

Mechanism for the origin and the evolutionary significance of heterochronia.

Using material on the evolution of the fundus of the oral cavity in amphibians, four principles were established for the origin of heterochronia: efficiency of ontogenesis; adaptability of an earlier (than in ancestors) beginning for functioning of traits; loss of the adaptive significance of a trait at a previous stage, but a preservation of it at a subsequent stage; and, a prolongation of the adaptive significance of a trait at later stages. The origin of heterochronia is associated with changes in the succession of the functioning of genes, with reorganization of systems of morphogenetic correlations, and with change in the traits themselves that undergo heterochronia. The uniqueness of heterochronia as an adaptation consists of an increase in the evolutionary flexibility of specific stages of ontogenesis.

Age Factors↗
PubMedDate not supplied

[The correlation of the ecological niches of the common (Rana temporaria L.) and of the moor (Rana arvalis Nilss.) frogs (Anura, Amphibia)].

During 25 years ecology and population dynamic of two brown frog species (Rana temporaria and R. arvalis) were studied in Moscow region, Solovki island and South Ural. We compared life cycles characteristics, namely biotope preferences, diet, migration, enemies, hibernation places using own and available literature data. Then we analyse how these parameters are changed among the species area and ecological niches were compared. We found that these two species do not compete in any stage of life cycle. Ecological niches are very closed and differences are determined generally by abiotic factors. So, R. temporaria prefers more wet biotope and more sensitive to acidity (low pH value). Differences in spawning time do not associate with interference in spawning places. We conclude that interspecific competition did not take place neither in the past nor in present and the reason of differences in ecological niches are determined by separate ways of evolutionary development of these species.

Animals↗