Since ancient times, scientists have tried to define the concept of "life." But to do this is quite difficult, because the organisms that inhabit the planet are very diverse. What are the criteria for living systems and the features of their functioning, you will learn from our article.
What is a system?
A system is a set of elements that are connected in a certain sequence. Such a structure ensures their integrity and ability to function. By origin, systems are artificial and natural. The first includes all the structures that man created. Their examples are diverse: from a ballpoint pen to a skyscraper. Agree, in the first and second cases, all the components of these systems are subject to clear laws and are connected in a certain order. Their slightest violation can change the whole mechanism of work.
Living systems are all the structures that surround us, but were not created by man. They are the "works" of nature. The microscopic cells of the amoeba, giant conifers, huge blue whales are all living systems. In these organisms, there really are many elements that interact in a certain way with each other. And what are the criteria for living systems in general? And do protein globules or water molecules belong to this concept? After all, they also consist of individual elements connected in a certain sequence. Scientists unequivocally claim that life is only a collection of elements enclosed in a cellular structure.
Levels of organization of living systems
Living systems in nature exist at different levels of organization, which differ in structural features and the interaction between their components. Molecular is also one of them, but its independent existence outside the cell is impossible. The most important process taking place at this level is the storage and sale of genetic material. Criteria of living systems are most evident on the example of a cell. It is she who is the structural and functional unit of all living things. The cells are plants, animals, fungi and bacteria. The exception is viruses, which are a combination of nucleic acid molecules and a protein.
Next is the complication of living systems. Cells combine into tissue. Each of them specializes in a specific function. The combination of tissues represents the next level - the body. However, in nature individuals do not exist separately. They interact with each other and with factors of inanimate nature. Moreover, they consistently form population-species, biogeocenotic and biospheric levels. The latter is the most global, uniting absolutely all living organisms that inhabit all habitats.
Chemical Features
The main properties of living systems, regardless of their level of organization, are characterized, first of all, by a certain chemical composition. The basis of these structures is formed by four chemical elements. These are carbon, oxygen, nitrogen and hydrogen. They are also called organogenic. They, in turn, form biopolymer molecules - proteins, carbohydrates, lipids and nucleic acids.
Metabolism
Any living organism is an open system. This means that there is a continuous exchange of substances with the environment. The intake of substances, their transformation, the elimination of end products of metabolism are integral signs of living systems. Entering the body, complex molecules break down with the release of a certain amount of energy. It is necessary for the implementation of growth and development.
Self-reproduction ability
The ability to reproduce or self-reproduce and regenerate are also criteria for living systems. These properties ensure continuity at all levels, making life possible on the planet as a whole. Reproduction methods depend on the structural features of the biological species. For example, bacteria multiply by dividing cells in two, plants vegetatively and through spores, and animals sexually.
Regeneration helps many organisms maintain their viability for as long as possible. Intestinal, worms, reptiles and plants are capable of restoring lost or damaged parts of the body. Especially active are the cells of freshwater hydra, whose body can recover from 1/200 part.
Motion
No wonder they say that movement is life. And indeed, moving in space, animals seek food, individuals of the opposite sex, or better living conditions. Their unicellular representatives move with the help of organelles - flagella, pseudopodia or cilia. Surprisingly, plants are also capable of movement. Everyone watched the leaves and flowers turn towards the light, and the shoots of vines encircled any surface. This is the growth movements of plants.
Growth and development
Growth and development are integral properties of living systems. The first involves quantitative changes in organisms. Growth occurs due to cell division. Moreover, in plants it is unlimited. This means that they grow throughout life. But animals - only until a certain period. Growth is accompanied by quantitative changes in the body - development. This process involves the acquisition of increasingly complex features of organization and physiology. Their position in the system of the organic world depends on the level of development of organisms . For example, angiosperms have become widespread due to progressive structural features, which include the presence of a flower and double fertilization.
Irritability
Another sign of living systems is their ability to respond to any changes in the environment. This property is called irritability. So, tulip flowers open in warmth, and mimosa leaves are folded during touch. In animals, irritability occurs through the nervous system and manifests itself in the form of reflexes. Some of them are congenital. These include respiratory, protective, grasping, sucking, blinking reflexes. They provide vitality from the first minutes of life. In the course of changes in existence, animals acquire new behavioral reactions.
The properties of living systems ensure their existence throughout their individual and historical development. These include the cellular structure, the unity of the chemical composition, metabolism, the ability to reproduce, grow, develop, irritability and adaptation.