in modern biology living matter is usually regarded as a hierarchical structure.Each level is a system of interrelated elements.At the same time a separate structural unit is both a set of "parts" of a lower order.Population-specific level of organization of life - one of those stages in the hierarchy of organisms.That it begin to fully manifest all evolutionary change.
Living Systems decided to combine into four groups:
Molecular genetic level.It houses such components of living organisms, lipids, carbohydrates, proteins and nucleic acids.This level can not be called alive, but macromolecules, its components provide the foundation for the next stage of development.
ontogenetic level.This is the place cells, organs, tissues and multicellular organisms, from Hydra to humans.It is at this level occurs first life.
population-species level.The exposition is dedicated to its features in this article.
biogeocenotic level.It includes a community of organisms and biocoenoses biosphere.This is the level at which the organization of living matter reaches its greatest complexity.
structures are placed at each level, are systemic.They tend to consist of a number of elements that constantly interact with the environment, manage internal processes through self-regulation.They have a boundary that defines where the system ends and begins outside world.Population-specific level - a structure with similar properties.The boundary that separates it from the environment is not some physical structure, but complex relationships of individuals and genetic factors.
population-species level of organization of life is essential for the understanding of evolutionary processes.It is at this stage are clearly visible all the basic mechanisms of selection.Top-level elements - the type and population.
species of living beings on our planet there are so many.The differences between them are determined on a set of characteristics.They are all different versions of the similarities of the same species:
morphological characters.In other words, the similarity of the external structure.
Uniformity of physiological and biochemical processes.At same species similarly proceeds metabolism same molecular composition of tissue and organs.
geographically.All of the species are located within the same area.
environmental attributes.Organisms belonging to the same species, similarly respond to changes in habitat conditions.For normal operation they require a certain level of temperature, humidity, lighting, and other parameters.
- genetic traits.For individuals of one species is characterized by the same nucleotide sequence of DNA.They have the same number of chromosomes.
absence of the main
any of these signs, taken separately, and found a group of individuals, does not guarantee that we face described element constituting the population-species living standards.Once all parameters are taken together, suggest that the group of organisms is integral.The morphological features may be similar to the so-called sibling species.Examples are roundworm, generally similar in structure, but different habitats.It also happens that the individuals of the same species differ in appearance.A common example - the difference in color and size of males and females of some birds and insects.The single area living in isolation from other indicators may also lead to the erroneous attribution to individuals of the same species.The area is often fragmented due to certain characteristics of the landscape.Conversely, in one area often live together individuals of very different kinds.
Similar examples can be found for any of the listed parameters.The elements that make up the population-species level of organization of life, can be discerned only by using the full set of features.However, the most essential is free interbreeding individuals and fertile offspring.On the basis of these attributes can be derived definition.View - a set of individuals that are similar in structure, internal and external, as well as of the processes of life, occupying one area and can interbreed with each other, leaving the ability to reproduce offspring.
population-species level, examples of which are found in any territory is that of the hierarchy of life, which fully unfold all the mechanisms of natural selection.It is here that the unit is a so-called evolution.This population, which is a structural element of both species.The latter is rather a systematic unity.In nature you can not find the form, not divided by the population.
This element included in the population-species level, there are several characteristics:
- all individuals belong to the same species;
- they inhabit relatively isolated area on the territory of this type;
- individuals interbreed freely and leave fertile offspring.
Separation of species populations often occurs as a result of geographical or biological isolation of one group from the other animals.In the first case, they are divided mountains, lakes, rivers, or other natural obstacles.In the latter - as a result of several different needs at ambient conditions, differences in the behavior or the presence of mutations is no possibility of crossing individuals of different groups.
populations have a set of indicators such as population, birth rate, mortality and gains.The first is the set of all individuals.Population distinguished by the ability to self-regulate their numbers.The limiting factor is the resistance of the medium: by increasing the number of individuals reduced food supply in the territory, the other conditions are deteriorating.The answer to this will decline - its reduction to a certain average.
important indicators of the element included in the population-species level of organization of the living are birth and death rates.They represent the number of dead fish appeared and for a certain period, respectively.The difference between them is called the gain.It can be negative or positive.In the first case, the population size is reduced, and in the second - is increasing.
Individuals structure of the element included in the population-species level of organization of life, vary by sex and age.These indicators form the basis of the allocation of appropriate structures.The ratio of males and females, as a rule, one to one, but due to the impact of external factors may arise disharmony in this parameter.The simultaneous presence in a population of individuals of different ages contributes to its greater adaptability.The increase in the number of "young" predicts increase in population in the future.
There are also behavioral structure characteristic only for animals.Individuals in the population can be solitary or form flocks, herds and families.First, sooner or later seek a society of their own kind, because otherwise it is impossible to reproduction.Flock is characterized by a large number of imitative responses, a clear internal procedure developed by the alarm system.During the breeding season, it usually splits into pairs.The family relationships become stronger offspring and parents.A good example of this type of behavioral patterns is a lion pride comprising one male, several females and their young.A herd - the most constant Animal Association.It is characterized by a strict hierarchy headed by the leader.
As already noted, population-species level of the organization - is the level in the hierarchy of living systems, which can be fully traced the evolutionary process.The changes begin with the population.Individuals, its components have the gene pool, that is a set of hereditary material of all organisms.It is characterized by the ability to directional change.The population is called a unit of evolution, as a separate body for life can not be changed due to the fixity of its set of genes.
change in the gene pool is the result of the emergence and accumulation of mutations.They appear very rarely and can affect any indication.There are dominant and recessive mutations.First, there immediately appear.Individuals with a new sign then subjected to natural selection.If the mutation is useful, it is fixed.Gradually, the population increase in the number of individuals with this trait.
Recessive mutations found in nature much more dominant, initially inactive.They accumulate in the gene for often quite long period.When a certain level of concentration of such mutations may occur as a new feature, and the process will be as described above.
the emergence of various characteristics of individuals on the basis of possible mixing (combined) in the gene pool of available material as a result of free mating.The number of possible variations will be greater than imposing population size.
in relatively calm, that is permanent, conditions in the population of individuals co-exist with a different set of features.This is supported by a mean composition of genes.In the case where an individual is subject to constant influence of aggressive environmental factors, will survive only the fittest organisms.This is how natural selection vigilantly "control" population-species level.Examples of its effects constitute the entire evolution of the animal world.Such changes in the gene pool is a prerequisite for all of the larger changes.
in the hierarchy of nature can not identify the most important and necessary structure.Each higher level of development is not possible without the "developments" of the previous.However, a new step always is qualitatively different from the simple sum of the underlying features.For example, population-species level of organization of living matter becomes "field activities" of natural selection, the main evolutionary process.