The term "population" is used today in various fields and fields of science. He has the greatest influence in biology, demography, ecology, medicine, psychometrics, cytology. But what is a population, and what is it characterized by?
A population is a group of individuals of the same species. Each of these organisms occupies a strictly limited and definite habitat. In other words, the population is a family of individuals that are part of a particular biocenosis. For free-living forms, the boundaries of propagation relative to the territory are determined by such factors as relief, climate, etc. For parasitic organisms, adaptivity and the life cycle are the barrier to resettlement.
To date, the study population mainly conducted to detect genetic or environmental sequences. This allows you to define the environment the survival of the species and their heredity. At the moment there is another concept – "cell population". This isolated the offspring of a specific number of groups of cells. The study of this sphere by specialists within Cytology. From the point of view of genetics, the population is a heterogeneous hereditary collection of forms of one species, to which the so-called pure line is opposed. The fact is that each family of individuals corresponds to specific features and represents a certain phenotype and genotype.
Before you start to understand more about what a population is, you need to know and understand its main components. There are 5 main characteristics:
1. Distribution. It can be spatial and quantitative. The first species, in turn, is divided into a 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 the population, which should not be confused with the subspecies distribution. Here the number represents the total number of organisms in a certain unit of space. Most often it is dynamic. Depends on the ratio of mortality and fertility of individuals.
3. Density. It is determined by biomass or by 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 time.
5. Mortality. It is divided according to age criteria. It represents the number of life forms perished per unit time.
At the moment there are the following types of populations: age, sex, genetic, environmental and spatial. Each of these variations has its specific structure. So, the age of the population is determined by the ratio of individuals of different generations. The same species can have both ancestors and piploda.
The sex population depends on the type of reproduction of the family and the set of deterministic morphofunctional and anatomical characteristics of organisms. The genetic structure is determined by variations in alleles and the way they are exchanged. The ecological population is a division of the family into groups with respect to environmental factors. The spatial structure depends on the distribution and placement of individual species in the range.
Separation of populations
In different families this property depends on the environment and forms of coexistence. If the same species is moving in large spaces, such population can be called large. In the case of weak development of the ability distribution, the family is determined by small populations, which may reflect, for example, the mosaic of the landscape. Population of animals with a sedentary lifestyle and plants depends on the heterogeneity of the environment.The level of isolation of neighboring families of one species is different. In this case, populations can be sharply distributed in space or be clearly localized in a certain territory. There is also a continuous colonization of a huge area with one species. In turn, the boundaries between populations can be blurred and discernible.
Interaction and attitude of species are carried out by means of individual contact. The shortest is the relationship of a predator to a prey. The longest contact occurs when interacting with parasitic organisms.
Population: population dynamics
To date, the survival curve plays an important role in the study of species. It determines the degree of population size. This characteristic of species depends on the ability of the family to survive.The dynamics of numbers can be of 3 types:
- most of the 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).
In some populations, this characteristic is due to significant fluctuations. The main factors affecting the abundance of the species are food, environment, predators, parasites, climate, etc.
View as a unit of structure
The population consists of a set of individuals who are similar by morphological and physiological properties, habitat, the type of crossing, the origins. This group of organisms is called a species. Is the unit structure of the population. Types depend on the following criteria: morphological, genetic, physiological, biochemical. By additional classification, the characteristics of influence are geographical and ecological.
Each species arises, then develops and adapts. With a sudden change in the conditions of the environment of existence, it can disappear.