Static parameters of community.

Quantity indicators (characteristics) of community can be divided into static and dynamic. Static parameters characterize a condition of community at present time, including number, density and also parameters of structure.

Number is a number of species in community. Number of community can be changed considerably in time. It depends on biotic potential of kind and external conditions.

Density is a number of species or biomass of community on unit of the area or volume.

Community is characterized by the certain structural organization - a relationship of species groups on sex, age, the size, a genotype, distribution of species on territory, etc. Thus, there are various structures of community: sexual, age, dimensional, genetic, spatially etc. On the one hand structure of community is formed on the basis of the general biological properties of species, on the other hand - under influence of environment factors, i.e. it has adaptive character.

According to the form of animal coexistence there are single ways of life, family, colonies, flights, herds. The single way of life is shown that species in communities are independent and isolated from each other (hedgehogs, pikes etc.). However it is characteristic only for the certain stages of life cycle. Completely single existence of organisms in the nature does not meet, as thus breeding would be impossible. The family way of life is observed in populations with strengthening communications between parents and posterity (lions, bears etc.). Colonies are group settlements of settled animals. Flocks are temporary associations of animals facilitating performance of any function: protection against enemies, migration (wolves, a herring, etc.). Herds are longer, than flocks, or constant associations of animals in which, as a rule, all vital functions of species are carried out, including protection against enemies, migrations, breeding, education of young growth, etc. (deers, zebras, etc.).

Genetic structure is a relationship of various genotypes and equilocal genes in the community. Totality of genes of all community species is called genofund. The genofund is characterized with frequencies of equilocal genes and genotypes. Frequency of equilocal genes is its share in all totality of equilocal genes of the given gene. The sum of frequencies of all equilocal genes is equal to unit.

According to Hard-Vainberg law, relative frequencies of equilocal genes in population are remained constant from generation to generation. Hard-Vainberg law is fair, if following conditions are observed: 1) the population is great; 2) in community free interbreeding is carried out; 3) there is no selection; 4) there are no new mutations; 5) there is no migration of new genotypes in community or from community.

The long and directed change of genetic structure of community, its genofund is called the elementary evolutionary phenomenon. Without change of the community genofund, evolutionary process is impossible.

The factors changing genetic structure of community are following:

1) Mutation is a source of new equilocal genes appearance;

2) Unequal capable of living of species (species are subjected to action of selection);

3) Not casual interbreeding;

4) Drift of genes is a change of equilocal genes frequency, which are casual and independent of selection action (for example, flashes of diseases);

5) Migrations are outflow of available genes and (or) inflow new ones

Лекция 3. Экология популяций - демэкология. Популяция. Классификация популяции

План

1. Понятие популяции.

2. Статические показатели популяции.

3. Динамические показатели популяции: рождаемость, смертность, скорость роста популяции.

4. Продолжительность жизни и выживаемость.

5. Экологическая стратегия выживания.

6. Регуляция численности (плотности) популяции.

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Дата добавления: 2015-10-29