Population structure

Population is characterized by a certain organization. Distribution of individuals in territory, relations of groups in gender, age, morphological, physiological, behavioral, and genetic characteristics reflect the structure of population. Population structure is formed on the one hand, on the basis of common biological properties of the species, on the other hand - under the influence of abiotic environmental factors and populations of other species. Population structure has, therefore, an adaptive character. Different populations of the same species possess as similar characteristics of the structure, as distinctive ones characterizing specific environmental conditions of their habitats.

Each population has quantitative characteristics that solve problems of a qualitative nature. There are two groups of quantitative indicators - statistical and dynamical.

Statistical indicators describe the state of the population at a given time. Statistical indicators include size of the population, density and performance structure.

Size of the population - the total number of individuals in the given area or in a given volume. Population size is never constant, and depends on birth and death ratio.

Density is determined by the number of individuals or biomass per unit of area or volume. Density is also variable, depending on the population size. With the population increasing, its density doesn't increase only if the population can expand its areal. Expansion can continue for as long as the population does not meet any obstacle.  We distinguish an accidentally even or group expansion.

Accidental expansion takes place only in a homogeneous environment, such as expansion of aphids in the field, but with the growth of reproduction the type of expansion can become group or spotty.

The most common is group expansion and it may be accidental. The group expansion provides for the highest resistance of the population to adverse conditions in comparison with an individual organism. Intensive expansion leads to rapid mixing of populations, blurs the boundaries between them. For example, highly mobile animals or birds have vast areals without sharp boundaries between populations. And as for slow-moving or passively moving animals, the boundaries of their populations are clearly distinguished, even in small areas.

Population density depends on the size of living organisms, the larger is an animal, the greater is the area they occupy, the lower population density, and vice versa.

Population size and density can also depend on other factors both biotic and abiotic: for example, the destruction of prey by predators, impact of parasites on life of hosts, cold winters and dry summers, etc. However, fluctuations in numbers are not unlimited. Population as any biological system has the ability to self-regulate. Maintaining optimal size of the population under these conditions is called homeostasis.

Any population is theoretically capable of unlimited growth, if it's not limited by factors of the environment. In this hypothetical case, the rate of population growth will depend on the biological potential specific to species. The concept of biological potential was introduced in ecology in 1928 by R. Chapman. This figure reflects the theoretical maximum of offsprings from a single pair (or one individual) per a unit of time, for example, for a year or the entire life cycle.

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$$$003-014-001$3.3.14.1 Методические указания к практическому занятию №14

{Цель занятия, методические указания к выполнению практического задания, примеры расчетов и задач}

1. What from does the population density depend?

2. What is the maintaining optimal size?

3. What is the biological potential?

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$$$003-014-002$3.3.14.2 Задания или тестовые вопросы для контроля к занятию №14

{Задания или тесты (при необходимости указать ключ для выбора варианта)}

Give Russian equivalents of the following expressions:

1.territory, 2.relations of groups in gender, 3. age, 4. morphological, physiological, behavioral, and genetic characteristics 5. Statistical indicators

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$$$003-015-000$3.3.15 Практическое занятие №15

{Тема, план занятия}