The concept of a system of multi-level organization of life is one of the key in modern science. All biological objects, according to her, are united on the basis of certain features and close relationships and are built in a certain hierarchical order. Similar principles are universal for nature as a whole. Familiarity with what biological systems are, it is better to start with the definition of a key concept.
Comprehensive Theory
The foundations of the concept were laid in the middle of the last century by Ludwig von Bertalanffy. It was he who developed the general theory of systems. It covers all objects of nature and society. The theory distinguishes biological, social, space, physical, economic, and other systems that unite into three large categories: microcosm, macrocosm, and megaworld. The first includes elementary particles and atoms, the second - everything, from molecules to the oceans and continents, the third - space objects. The macrocosm includes living systems.
Basic concept
A system is an association of elements based on certain relationships subject to certain laws. The organization of such a structure, as a rule, consists of several ordered levels. Moreover, each element can simultaneously be a system of a lower order. An important property of such an organization: the whole is qualitatively different from the sum of all its components. A system is not just a set of characteristics of elements; it is distinguished by a certain new quality.
All objects of the living world are similar structures. Moreover, the quality arising from the combination of several elements becomes a new manifestation of life.
Open
Understanding what biological systems are requires a description of yet another property of such structures. This is an interaction with the environment. In theory, the organization of biological systems can be either closed or open. In practice, scientists do not know a single completely closed structure. Any living system constantly interacts with the environment through some semi-permeable boundary shell. For cells, this is a bilipid membrane; for a space station, it is sheathing. Social systems are combined through legislation or certain relationships between people.
It turns out, the answer to the question "What is a biological system?" can be formulated as follows: this is a set of constantly interacting living elements, built in a certain hierarchical order and open to one degree or another for exchange with the environment.
Signs
All the distinctive characteristics of the structures under consideration are at the same time criteria for distinguishing living nature from nonliving. We call the signs of biological systems with their brief characteristics:
- Unified chemical composition. All natural objects are built from the same molecules. However, living matter as the main elements includes carbon, nitrogen, oxygen and hydrogen.
- Metabolism with the environment. This is the already described property of the openness of the system. One of its manifestations is the energy dependence of such structures.
- Self-reproduction (reproduction).
- Heredity - the property of transmitting structural features and functioning from generation to generation.
- Variability is the ability to acquire new characteristics and skills throughout life.
- Growth and development. They are directed irreversible change. The individual and historical development of living systems, called ontogenesis and phylogenesis, respectively, is distinguished.
- Irritability (reflexes, taxis) - the ability to respond to stimuli and environmental changes.
- Discreteness. Any living system consists of separate, but interacting elements that form a hierarchical structure.
- Self-regulation. There are internal mechanisms for maintaining homeostasis that contribute to system survival. Self-regulation is based on the principle of negative feedback.
- Rhythm. Strengthening and weakening of various processes at regular intervals.
Levels of organization of biological systems
All the described properties are stored at any stage of the hierarchical structure. The main levels of organization of biological systems stand out quite arbitrarily, since any of them can easily be divided into several components. In general, they talk about the four steps of this hierarchy:
- molecular genetic level;
- ontogenetic level;
- population and species level;
- biogeocenotic level.
Let us dwell on them in more detail.
Molecular genetic level
Macromolecules such as proteins, lipids, carbohydrates and nucleic acids are structural elements of organisms, but they themselves are not carriers of a full life.
Each of these elements performs its functions. Carbohydrates are a source of energy. Lipids are part of the plasma membrane of cells. They are also an energy supplier. Proteins perform most of the vital functions. They consist of twenty varieties of amino acids that can alternate in random order. As a result, there is a huge amount of proteins that can cope with a variety of jobs. Nucleic acids, DNA and RNA, are the basis of heredity.
Macromolecules combine into complexes to form organelles of the cell: ribosomes, mitochondria, myofibrils, and so on. All of them are responsible for individual biological manifestations, but do not reach the level of complexity that can be called life.
Next step
What biological systems make up the ontogenetic level? These are all organisms, ranging from unicellular to mammals and humans, as well as organs, tissues and body cells. All of these elements can be considered as separate levels of organization of biological systems, however, for convenience and by virtue of general laws, they are combined.
A cell is an elementary structural unit of the structure of organisms. It also represents the level of complexity of the biological system at which life as a phenomenon first appears. As already mentioned, simpler structures provide only individual functions. The cell is inherent in all the properties of biological systems.
Tissues and organs are intermediate sublevels of the ontogenetic stage. They are followed by a multicellular organism. It is characterized by the ability to independent existence, development and reproduction. This property distinguishes an individual and a cell from organs and tissues.
Population and species
From step to step there is a complication of biological systems. At the next level are species and populations. The first are a collection of individuals characterized by hereditary similarities in a number of parameters: morphology, physiology, genetics, geographical location. And most importantly: the organisms that make up the species are able to interbreed freely and leave fertile offspring.
A group of individuals occupies a certain territory, which is called the habitat. Quite often it is torn apart by various geographical obstacles. As a result, the species breaks up into several relatively isolated populations. Naturally, the conditions of separation from the rest of the species contribute to the accumulation of certain genetic material. With a strong discrepancy in the characteristics of populations, new species appear.
Ecosystems
In the hierarchical ladder, populations and species are followed by community, biogeocenosis, and biosphere. The first is a collection of populations of different species located on the same territory. There are plant, animal and microbial communities. Their combination within the same range will be called a biocenosis. These levels of biological systems are characterized by the close interconnection of all individuals.
The conditions in which organisms exist constantly affect them. The whole set of such factors of the inanimate nature of this area is usually called a biotope. The environment and communities of organisms are in constant interaction, a cycle of matter and energy occurs. Therefore, the biotope and biocenosis are combined into a biogeocenosis, or ecosystem. This level is also characterized by all the features of the living: it is constantly in contact with the environment, control in it is based on the principle of self-regulation, processes are subject to certain cycles.
At the highest level of the hierarchy is the biosphere of the Earth - the shell inhabited by living beings. A huge influence on it is exerted by human activity, which increasingly leads to the emergence of environmental disasters.
What are biological systems? In fact, this is all living things that surrounds us. Man differs from other elements in the biosphere by the ability to realize, and therefore, redirect and change his activity. So far, this ability of Homo sapiens works against nature. However, it is thanks to her that we have a chance to fix everything.