Ecology: Biology of Interactions. I-03. Levels of Biosystem Organization

I-03. Levels of Biosystem Organization
A system is a complex of elements in interaction.
Ludwig von Bertalanffy
I believe it is as impossible to know the parts without knowing the whole as it is to know the whole without knowing the parts.
Blaise Pascal
Ecology examines the relationships of living systems — organisms, populations, ecosystems, and the biosphere — with their environment. To understand the diversity of these biosystems, one must examine the concept of ‘system’ itself. It derives from the Greek systema — composed of parts; connection. According to one of the simplest yet perfectly adequate definitions, a system is an ordered whole consisting of interrelated parts.
Aristotle, the ‘father of all sciences’, is credited with the aphorism: ‘the whole is greater than the sum of its parts’. What did he mean? Clearly, in some cases (for example, in addition) the whole is exactly the sum of its parts! For instance, the weight of a computer is precisely equal to the combined weight of all its components. But can the individual components of a computer, taken separately, process data, transform and reproduce images, receive and transmit information? Of course not — components acquire these properties only when assembled in a specific way. This is why, in defining a system, we emphasize that it is an ordered whole.
Thus, the properties of systems can be divided into two groups: those that are the sum of the properties of its parts, and those that arise in the system as a unified whole. Let us name these properties. Additive properties of a system (Latin additio — addition) are the sum of the properties of its parts. Qualitatively new properties of the system are called emergent (Latin emergere — to emerge, to appear). The English adjective ‘emergent’ is most often rendered as ‘emerdzhentnyi’, which does not follow the convention for rendering the letter ‘g’ in words: after all, we say and write ‘hen’ not ‘djen’, despite the English ‘gen’!
Biological systems are organized hierarchically, and at each level regulation is carried out using similar principles. In the late 20th century, the systems approach stemming from Ludwig von Bertalanffy gained development. It is based on the premise that systems built from similarly interrelated parts have similar holistic (emergent) properties.
By comparing systems of different levels, one can find much in common between them, and also identify features specific to each level. Reflection on these regularities gave rise to the concept of structural levels of biosystem organization, which began to develop in the 1930s and was fully formed in the 1960s. The following levels of biosystem organization are customarily distinguished: molecular — (genetic) — (subcellular) — cellular — (organ-tissue) — (functional systems) — organismal — population — biogeocenotic — biospheric. In the list above, the levels in parentheses can be considered relatively less important than those without parentheses.
Different levels of biosystems should be distinguished because each is characterized by properties absent at lower levels. A universal list of levels of biosystem organization cannot be compiled. Depending on which biosystems are studied and from which perspective, more or fewer levels need to be distinguished, at each of which qualitative emergent properties arise. It is useful to distinguish as many levels as are needed so that each possesses properties whose study at lower and higher levels would be impossible. A complete study of a system must also include the study of higher and lower systems (‘supersystems’ and subsystems).
Thus, the demographic structure of a population is absent at the level of an individual organism, while the phenomenon of human consciousness is absent at the level of individual brain structures. The phenomenon of life arises at the cellular level, while the phenomenon of potential immortality — at the population level. The organism is the unit of natural selection. The specificity of the biogeocenotic level is associated with the composition of its components and the cycling of matter (accompanied by flows of energy and information), while the biospheric level — with the closedness of the matter cycle. Examples of emergent properties of some biosystems are given in Table I-03.1.
Table I-03.1. Examples of biosystems at different levels and their emergent properties

Level	Example	Emergent properties
Molecular	Protein molecule	Has a specific conformation; capable of performing its functions in the cell
Cellular	Cell	Possesses the basic properties of living systems: capable of metabolism, reproduction, etc. In unicellular organisms it has the properties of an organism; in multicellular organisms it is designated to perform a specific function
Organ-tissue	Neural network	Controls cellular vital activity (division, metabolism, functional activity). Capable of processing information and performing definite cybernetic functions
Organismal	Individual organism	Is the unit of natural selection: as a whole it dies or survives and reproduces. Has individuality that arises as a result of ontogenesis
Population	Population of separate-sex organisms	Is potentially immortal and capable of evolution. Characterized by a specific sex-age, spatial, genetic, and hierarchical structure
Biogeocoenotic	Biogeocoenosis	Capable of development (succession); carries out a partially closed cycle of matter
Biospheric	Biosphere	Carries out closed biogeochemical cycles (accounting for exchange of matter with space and the Earth’s interior). Regulates certain properties of the planet (Gaia hypothesis). Capable of biospheric evolution

I-03. Levels of Biosystem Organization
A system is a complex of elements in interaction.
Ludwig von Bertalanffy
I believe it is as impossible to know the parts without knowing the whole as it is to know the whole without knowing the parts.
Blaise Pascal
Ecology examines the relationships of living systems — organisms, populations, ecosystems, and the biosphere — with their environment. To understand the diversity of these biosystems, one must examine the concept of ‘system’ itself. It derives from the Greek systema — composed of parts; connection. According to one of the simplest yet perfectly adequate definitions, a system is an ordered whole consisting of interrelated parts.
Aristotle, the ‘father of all sciences’, is credited with the aphorism: ‘the whole is greater than the sum of its parts’. What did he mean? Clearly, in some cases (for example, in addition) the whole is exactly the sum of its parts! For instance, the weight of a computer is precisely equal to the combined weight of all its components. But can the individual components of a computer, taken separately, process data, transform and reproduce images, receive and transmit information? Of course not — components acquire these properties only when assembled in a specific way. This is why, in defining a system, we emphasize that it is an ordered whole.
Thus, the properties of systems can be divided into two groups: those that are the sum of the properties of its parts, and those that arise in the system as a unified whole. Let us name these properties. Additive properties of a system (Latin additio — addition) are the sum of the properties of its parts. Qualitatively new properties of the system are called emergent (Latin emergere — to emerge, to appear). The English adjective ‘emergent’ is most often rendered as ‘emerdzhentnyi’, which does not follow the convention for rendering the letter ‘g’ in words: after all, we say and write ‘hen’ not ‘djen’, despite the English ‘gen’!
Biological systems are organized hierarchically, and at each level regulation is carried out using similar principles. In the late 20th century, the systems approach stemming from Ludwig von Bertalanffy gained development. It is based on the premise that systems built from similarly interrelated parts have similar holistic (emergent) properties.
By comparing systems of different levels, one can find much in common between them, and also identify features specific to each level. Reflection on these regularities gave rise to the concept of structural levels of biosystem organization, which began to develop in the 1930s and was fully formed in the 1960s. The following levels of biosystem organization are customarily distinguished: molecular — (genetic) — (subcellular) — cellular — (organ-tissue) — (functional systems) — organismal — population — biogeocenotic — biospheric. In the list above, the levels in parentheses can be considered relatively less important than those without parentheses.
Different levels of biosystems should be distinguished because each is characterized by properties absent at lower levels. A universal list of levels of biosystem organization cannot be compiled. Depending on which biosystems are studied and from which perspective, more or fewer levels need to be distinguished, at each of which qualitative emergent properties arise. It is useful to distinguish as many levels as are needed so that each possesses properties whose study at lower and higher levels would be impossible. A complete study of a system must also include the study of higher and lower systems (‘supersystems’ and subsystems).
Thus, the demographic structure of a population is absent at the level of an individual organism, while the phenomenon of human consciousness is absent at the level of individual brain structures. The phenomenon of life arises at the cellular level, while the phenomenon of potential immortality — at the population level. The organism is the unit of natural selection. The specificity of the biogeocenotic level is associated with the composition of its components and the cycling of matter (accompanied by flows of energy and information), while the biospheric level — with the closedness of the matter cycle. Examples of emergent properties of some biosystems are given in Table I-03.1.
Table I-03.1. Examples of biosystems at different levels and their emergent properties

Possesses the basic properties of living systems: capable of metabolism, reproduction, etc. In unicellular organisms it has the properties of an organism; in multicellular organisms it is designated to perform a specific function

Regulates cellular vital activity (division, metabolism, functional activity). Capable of information processing and performing certain cybernetic functions

Is the unit of natural selection: as a whole it dies or survives and reproduces. Has individuality that arises as a result of ontogenesis

Is potentially immortal and capable of evolution. Characterized by a specific sex-age, spatial, genetic, and hierarchical structure

Carries out closed biogeochemical cycles (accounting for exchange of matter with space and the Earth’s interior). Regulates certain properties of the planet (Gaia hypothesis). Capable of biospheric evolution

The identification of supra-organismal structural levels of biosystems can be carried out according to two different principles. From an ecological (functional-energetic) perspective, a population is part of a biogeocenosis, and a biogeocenosis is part of the biosphere. This approach generally corresponds to the ecological definition of a population. From a phyletic (related to phyla — evolutionary branches), i.e., genetic-evolutionary perspective, a population is part of a species and supra-specific taxa (see point IV-01).