Population types in biology. A population is... Characteristics and types of populations. Three Types of Survival

Tell me, do you know what ecology is? If your answer is something like this: “Ecology is something that has to do with the cleanliness of the environment,” you will end up in milk. Ecology has a rather indirect relationship to this issue.


What touches me most is when they say: “There and there the environment is bad.” It is clear what exactly the person wants to say, but still, these words are as absurd as if someone said: “Trigonometry is bad in this area.”

Ecology is not a phenomenon, it is a science. How can science be bad? Yes, it may be imperfect, undeveloped, it may even be pseudoscience, but it cannot be “bad”.

The second aspect of the misconception is that ecology does not deal with issues of environmental purity, but studies the interaction of various living organisms with each other and with the inanimate nature that surrounds them. Ecology studies the structure of systems at the supraorganismal level, one of which is population- a concept the study of which is included in the objectives of this article.

What is a population?

Population... What is this thing? We've all heard this word, but do we all really understand its meaning?

The name of this concept comes from the Latin word population, which translated means “population”. So a population is a population? Yes, of course, but... can every population be called a population? Let's figure it out.


Firstly, when we talk about a population, we always mean representatives (individuals) only one kind. If we are talking about representatives of different species, this is no longer a population, but a community, called in scientific parlance.

Secondly, by population we mean long-term the habitat of these same species in the same territory.

Thirdly, for a population, a prerequisite is relative isolation its representatives from groups with which genetic exchange is possible. This isolation can be of either a territorial or some other nature. In other words, a population includes individuals for whom the possibility of interbreeding is much higher than the possibility of interbreeding with representatives of other groups.

Population division

A population can be subdivided into smaller elements.

Dem is a small population of individuals living in a limited area, within which no significant changes occur in the gene pool. Usually it spreads over several generations and consists of several dozen individuals.

Parcel is a group of living organisms that live in close proximity to each other and are constantly in contact with each other.

Family- she is family. Here, explanations will probably be unnecessary. This is the smallest cell of the population.

Population characteristics

The population has the following characteristics:

— total number of individuals;

— density, reflecting the average number of individuals per unit area;

— the nature of the distribution of individuals in space;

— orderliness of the structure.

Population structure

From a structural point of view, the population is considered in the following aspects:

— genetic structure;

— age structure;

- sexual structure;

- morphological (internal and external structure) structure.

There are also other parameters by which the structure of a particular population is determined.

Population dynamics

There is such a thing as a logistic equation or Verhulst equation, which reflects the process of population growth. This equation reflects two premises:

1. The rate of population growth is proportional to its current size;

2. The rate of population growth is proportional to the amount of available resources.


According to this equation, the number of individuals in a population initially grows approximately exponentially, but once it reaches the point at which competition for resources begins, growth begins to slow down and eventually stops altogether. As growth slows, the number of individuals stabilizes at a decreasing exponential rate.

The term “population” is used today in various fields and areas of science. It has the greatest influence in biology, demography, ecology, medicine, psychometrics, and cytology. But what is a population, and how is it characterized?

Introduction. Definitions

To date, population studies have primarily been conducted to identify genetic or environmental sequences. This makes it possible to determine the survival environment of species and their heredity. At the moment, there is another concept - “cell population”. This is the isolated offspring of a specific number of group of cells. This area is studied by specialists within the framework of cytology.

From the point of view of genetics, a population is a heterogeneous hereditary collection of forms of one species, which is opposed to the so-called pure line. The fact is that each family of individuals meets specific characteristics and represents a certain phenotype and genotype.

Main characteristics

Before you begin to understand in more detail what a population is, you need to know and understand its main components. There are 5 main characteristics in total:

1. Distribution. It can be spatial and quantitative. The first type, in turn, is divided into random and uniform distribution. The quantitative indicator is responsible for the size of the population or its individual group. The distribution of individuals directly depends on climatic conditions, genome, food chain and degree of adaptation.

2. Number. This is a separate characteristic of a population and should not be confused with a subtype of distribution. Here, abundance represents the total number of organisms in a particular unit of space. Most often it is dynamic. Depends on the ratio of mortality and fertility of individuals.

3. Density. Determined by biomass or the number of organisms per unit area (volume).

4. Fertility. It is determined by the number of individuals that appeared as a result of reproduction per unit of time.

5. Mortality. Divided according to age criteria. Represents the number of life forms killed per unit of time.

Structural classification

At the moment, the following types of populations are distinguished: age, sex, genetic, environmental and spatial. Each of these variations has its own specific structure. Thus, the age population is determined by the ratio of individuals of different generations. Representatives of the same species can have both ancestors and offspring.

The sexual population depends on the type of reproduction of the family and the set of determined morphofunctional and anatomical characteristics of organisms. Genetic structure is determined by variations in alleles and the way they are exchanged. An ecological population is a division of a family into groups relative to environmental factors. Spatial structure depends on the distribution and placement of individual individuals of the species in the area.

Isolation of populations

In different families, this property depends on the environment and the form of coexistence. If representatives of one species move over large areas, then such a population can be called large. In the case of weak development of distribution abilities, the family is determined by small aggregates, which can reflect, for example, the mosaic nature of the landscape. The population of sedentary animals and plants depends on the heterogeneity of the environment.

The level of isolation of neighboring families of the same species varies. In this case, populations can be sharply distributed in space or be clearly localized in a certain area. There is also a complete colonization of a huge area by one species. In turn, the boundaries between populations can be blurred and distinguishable.

Population dynamics can be of 3 types:

Most individuals survive to the maximum age threshold (humans and mammals),

Death can occur at any time (reptiles and birds),

The mortality rate is high already in the early stages of development (fish, plants, invertebrates).

A population consists of a collection of individuals that are similar to each other in morphophysiological properties, area, type of crossing, and origin. Such a group of organisms is called a species. It is a unit of population structure.

Types depend on the following criteria: morphological, genetic, physiological, biochemical. According to an additional classification, the characteristics of influence are geographical and environmental.

Each species arises, then develops and adapts. With a sharp change in environmental conditions, it may disappear.

In biology, there are many concepts and many definitions of species. One of the simplest definitions of a species says: a species is a collection of organisms (individuals) similar to each other in a number of essential characteristics, inhabiting a certain area, capable of interbreeding with each other and producing fertile offspring similar to their parents.

A habitat is a section of the earth's surface (territory or water area) on which a given type of organism exists and reproduces. In most cases, the habitat area is so large that organisms of the same species must adapt to the effects of environmental factors in different conditions. Thus, the species has a certain ecological structure.

A population is a minimal self-reproducing group of individuals of the same species, inhabiting a certain area for a long series of generations, forming its own genetic system, forming its own ecological niche and more or less isolated from other similar groups of this species.

A population is a form of existence of a species and an elementary unit of evolution.

The main property of populations, like other biological systems, is that they are in continuous movement and constantly changing. This is reflected in all parameters: productivity, stability, structure, distribution in space. Populations are characterized by specific genetic and environmental characteristics that reflect the ability of systems to maintain existence in constantly changing conditions: growth, development, stability. The science that combines genetic, ecological, and evolutionary approaches to the study of populations is known as population biology.

Types of populations. Populations may occupy areas of different sizes, and living conditions within the habitat of one population may also not be the same. Based on this characteristic, three types of populations are distinguished: elementary, ecological, and geographical.

1. An elementary (local) population is a collection of individuals of the same species occupying a small area of ​​homogeneous area. There is a constant exchange of genetic information between them.

EXAMPLES. One of several schools of fish of the same species in the lake; microgroups of Keiske lily of the valley in white birch forests, growing at the bases of trees and in open places; clumps of trees of the same species (Mongolian oak, larch, etc.), separated by meadows, clumps of other trees or shrubs, or swamps.

2. Ecological population - a set of elementary populations, intraspecific groups, confined to specific biocenoses. Plants of the same species in a cenosis are called a cenopopulation. The exchange of genetic information between them occurs quite often.

EXAMPLES. Fish of the same species in all schools of a common reservoir; squirrel populations in pine, spruce-fir, and broadleaf forests in one area.

3. Geographic population - a set of ecological populations that inhabit geographically similar areas. Geographic populations exist autonomously, their habitats are relatively isolated, gene exchange occurs rarely - in animals and birds - during migration, in plants - during the spread of pollen, seeds and fruits. At this level, the formation of geographical races and varieties occurs, and subspecies are distinguished.

EXAMPLES. The geographical races of Dahurian larch (Larix dahurica) are known: western (west of the Lena (L. dahurica ssp. dahurica) and eastern (east of the Lena, distinguished in L. dahurica ssp. cajanderi), northern and southern races of the Kuril larch. Similarly identification by M.A. Shemberg (1986) of stone birch of two subspecies: Erman's birch (Betula ermanii) and woolly birch (B. lanata).In the lower reaches of the Yama River there is a center of Norway spruce (Picea obovata), separated from the continuous massif of spruce forests to the east 1000 km, to the north - 500 km. Zoologists distinguish tundra and steppe populations of the narrow-skulled vole (Microtis gregalis). The species "common squirrel" has about 20 geographical populations, or subspecies.

A population is individuals belonging to the same biological species, capable of free interbreeding and having a common gene pool. has numbers, mortality, birth rates, dynamics, range, density. The population structure also includes the ratio of females and males, ages, and spatial distribution system.

The size of the range is set in accordance with the radius of a single (individual) activity and represents the distance between the point of death and the point of birth of most individuals. So, for example, for a lizard this radius is thirty meters, for a muskrat it is about four hundred, for a rabbit and a sparrow it is three kilometers. In plants, the size of their range is set according to the distance the pollen travels. So, for example, the activity radius of a pine tree is about one hundred and twenty, and that of corn is about fifteen meters.

The area and shape of the habitat in each individual case is established in accordance with the landscape features of the territory. Intrapopulation distinctive features, as well as geographic (territorial) connections of individuals, are also important.

Most often, the following types of populations are distinguished: geographical, ecological, and local.

Ecological is a collection of individuals that lives within one system. Moreover, the boundaries coincide with the boundaries of the ecosystem itself, determined by vegetation and phytocenosis.

A local population is a local collection of populations of a particular species. Individuals live in various ecosystems of a particular area. Thus, a local population of a house sparrow is a collection of populations of individuals from settlements located at a distance of less than three kilometers from each other.

Geographic is a collection of individuals occupying an area with geographically homogeneous conditions. From Kamchatka to Brest, for example, twenty-nine populations of common squirrels have been identified. A geographic population is a territorial race, subspecies. The individuals are phenotypically similar.

Population (population) is, first of all, an elementary unit of the evolutionary process. Together with it, it is also the main spatial unit of a certain type. Thus, a population can be characterized as a collection of individuals not only occupying a certain territory (space), but also capable of reproducing over a long period of time. The integrity of the population from the point of view of evolution is associated mainly with panmixia (free crossing), which, to one degree or another, within one set of species is higher than between neighboring peoples. At the same time, despite its integrity, the population is heterogeneous in terms of genetic characteristics. The main characteristics of the species are fixed hereditarily.

There is a classification of the population from a medical point of view.

So, for example, a closed collection of individuals is isolated. In this case, one population is isolated from others by gender.

There is also an ideal set of individuals. In this case, we consider a hypothetical panmictic (capable of interbreeding) population with a large population that persists through generations. Such a set of species is not affected by mutation pressure or external factors. The concept of an ideal population is used in modeling the evolutionary process.

Individuals of the same species can be genetically identical. In this case we are talking about an isogenic population.

The collection may be open. In this case, migrating individuals introduce new genes into it.

A microbial population is a collection of cells of a particular strain.