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Population biology

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POPULATION BIOLOGY

Everything is connected on earth- states the first law of ecology. Meaning that we cant even make one step without disruption the environment. Even a usual step on the lawn is tens of ruined microorganisms and scared insects that might be changing their migration paths and reducing their natural efficiency. During the last century humans have gotten to be alarmed about the destiny of the planet, however, when we stepped into this century, we have stepped into the ecological crisis that we ourselves created.

Environmental contamination, exhaustion of natural resources and infringements of ecological communications in ecosystems became global problems. And if the mankind will continue to continue obusing environment, its death is inevitable.

Now, during an approaching ecological crisis on the planet, it is necessary for us to cooperate and preserve nature.

By consuming natural resources more intensively human beings have progressed and improved conditions of development and the growth of Homo sapiens as a biological species. However, by "winning" the nature, we have created almost crisis situation in interaction between the person and the nature, fraught with greater dangers to the future of our civilization. It could be clearly seen in the problems with natural resources, power, quality of an environment in its communication with the further industrial development in the world and growth of the population. Interdependent changes have led to occurrence of new communications between global economy and global ecology. In the past we were alarmed about the consequences of an economic growth for an environment. Now we can not simply ignore the consequences of " ecological stress " – the deterioration of grounds, a water polution, a condition of an atmosphere and forests.

Now becomes more clear, that sources and the reasons of pollution are much more various, complex and interconnected, and consequences of pollution carry wider, cumulative and chronic character, than it was considered earlier. Science has already given a definition of anthropogenous environmental contamination. It is physical, chemical and biological change of the quality of an environment (atmospheric air, waters, ground) as a result of the economic or other activity, exceeding the established specifications of harmful influence on an environment and creating threat to health of the person and to the conditions of flora and fauna.

The practical output of ecology can be first seen in making the decisions in the questions of wildlife management; it should create a scientific basis of operation of natural resources. We can ascertain, that neglect of the laws underlying natural processes has led to the serious conflict between the person and the nature.

CONCEPT OF THE POPULATION

Population ecology is defined as group of organisms of one kind (inside of which individual can exchange the genetic information), occupying concrete space and functioning as a part biotic community.

The population is a set of individuals of one kind living in certain territory, freely crossed among themselves and it is partially or completely isolated from other populations.

The population has its own characteristics: number, its density, spatial distribution of individuals. It could be distinguished by age, sexual and dimensional structure.

Structure. It is possible to allocate three ecological age groups: prereproductive - group of individuals, which age has not reached ability of reproduction; reproductive - the group reproducing new individual; postreproductive - the individuals who have lost ability to participate in reproduction of new generations. Duration of these ages in relation to the general life expectancy strongly varies between different organisms.

Number and density express quantitative characteristics of a population as the whole. Number of a population is expressed by number of individuals of the given kind living on the unit of the area borrowed by it. Dynamics of the population numbers in time is defined by a parity of parameters of birth rate, death rate, survival rate which in turn are defined by conditions of life.

The density of a population is the size of population dependant upon the space taken by it: number of individuals, or biomass, of the population per unit of an area or volume. The density depends on a trophic level on which there is a population. The lower a trophic level, the higher the density.