Ecology: the Biology of Interactions. 1.05. Levels of Organization of Biosystems
Biological systems are organized hierarchically, and at each level regulation is carried out using similar principles. The systems approach that gained development at the end of the twentieth century, going back in its development to Ludwig von Bertalanffy, is connected with the fact that systems composed of similarly interconnected...
Ukrainian language (latest version) / Russian language (updates discontinued) 1.04. The History of Ecology
1.04. History of Ecology
D. Shabanov, M. Kravchenko. Ecology: the Biology of Interactions Chapter 1. Ecology and the Biosystems It Studies
1.06. Approaches to the Study of Biosystems
1.05. Levels of Organization of Biosystems All living matter rises before us as a single whole, as one enormous organism, borrowing its elements from the reservoir of inorganic nature, purposefully governing all the processes of its progressive and regressive metamorphosis, and finally giving back to dead nature everything it had borrowed. S. N. Winogradsky. Lecture before the imperial family, 8 December 1896 Ecology considers the relationships of living systems with their environment: organisms, populations, ecosystems, the biosphere. To make sense of the diversity of these biosystems, one must consider the very concept of a “system.” It comes from the Greek systema, composed of parts; a union. According to one of the simplest, but entirely suitable, definitions, a system is an ordered whole consisting of interconnected parts. Aristotle, the “father of all sciences,” is credited with the aphorism: “the whole is more than the sum of its parts.” What did he mean? Clearly, in some cases (for example, in addition), the whole is precisely the sum of its parts. For example, the weight of a computer is exactly equal to the weight of all its components. But do the components of a computer, taken separately, possess the ability to process data, transform and reproduce images, receive and transmit information? Naturally, computer components acquire these qualities only when joined in a definite way. That is precisely why, in defining a system, we emphasized 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 their parts, and those that arise in the system as a unified whole. Let us name these properties. The additive properties of a system (Latin additio, addition) are the sum of the properties of its parts. Qualitatively new properties of a system are called emergent (Latin emergere, to arise, to appear). Biological systems are organized hierarchically, and at each level regulation is carried out using similar principles. At the end of the twentieth century, the systems approach received renewed development, going back to Ludwig von Bertalanffy. It is based on the fact that systems composed of similarly interconnected parts possess similar integral (emergent) properties. Comparing systems of different levels, one can see much that is common between them, while also finding features specific to each level. Reflection on these regularities gave rise to the concept of structural levels of organization of biosystems, which began developing in the 1930s and took final shape in the 1960s. Thus, it is customary to distinguish the following levels of organization of biosystems: molecular — (genic) — (subcellular) — cellular — (organ-tissue) — (functional systems) — organismal — population — biogeocoenotic — biospheric. In this list, the levels in parentheses may be regarded as relatively less important than those without parentheses. Different levels of biosystems should be distinguished because each level is characterized by properties absent from the lower ones. It is impossible to compile a universal list of levels of organization of biosystems. Depending on which biosystems are being studied and from what standpoint, more or fewer levels should be distinguished, at each of which some emergent properties arise. It is expedient to distinguish such a number of levels that each has properties whose study is impossible at both the lower and the higher levels. Complete study of a system should 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 the 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, and the phenomenon of potential immortality at the population level. The organism is the unit of natural selection. The specificity of the biogeocoenotic level is associated with the composition of its components and the cycling of matter (accompanied by flows of energy and information), whereas the specificity of the biospheric level is associated with the closure of matter cycles. Examples of emergent properties of certain biosystems are given in Table 1.5.1. Table 1.5.1. Examples of biosystems of different levels and their emergent properties Level Example Emergent properties Molecular Protein molecule Has a characteristic conformation and is capable of performing definite functions in the cell
Level
Example
Cellular Cell
Possesses the basic properties of living systems: capable of metabolism, reproduction, etc. In unicellular organisms it possesses the properties of an organism; in multicellular ones it is designed to perform a definite function
Protein molecule
It has a characteristic conformation, capable of performing specific functions in the cell
Cellular
Cell
Organ-tissue Neural network Controls cellular vital activity (division, metabolism, functional activity). Capable of processing information and performing definite cybernetic functions
Organ-tissue
Neural network
Organismal Individual organism Is the unit of natural selection: as a whole it dies or survives and reproduces. Possesses individuality arising as a result of ontogenesis
Organismal
Individual
Population Population of separate-sex organisms Possesses potential immortality and the capacity for evolution. Characterized by a definite sex-age, spatial, genetic, and hierarchical structure
Популяційний
Population of separate-sex organisms
Biogeocoenotic Biogeocoenosis Capable of development (succession), carries out a partially closed matter cycle
Biospheric
Biosphere
Carries out closed biogeochemical cycles (taking into account exchange of matter with space and the Earth’s interior). Regulates certain planetary properties (Gaia hypothesis). Capable of biospheric evolution
Біосферний
Biosphere
The identification of supraorganismal structural levels of biosystems can be carried out according to two different principles. From an ecological (functional-energetic) point of view, the population is part of the biogeocoenosis, and the latter is part of the biosphere. This approach mainly corresponds to the ecological definition of population. From a phyletic (connected with phyla, evolutionary branches), that is, genetic-evolutionary point of view, the population is part of the species and of supraspecific taxa (which corresponds to the genetic approach to the definition of population; see section 4.1). Additional materials: Educational model: Levels of Biosystems Column: Multilevel Frogs Ukrainian / Russian
1.04. The History of Ecology
D. Shabanov, M. Kravchenko. Ecology: the Biology of Interactions Chapter 1. Ecology and the Biosystems It Studies
1.06. Approaches to the Study of Biosystems
1.06. Approaches to Studying Biosystems