Levels of organization of living matter

Principles and properties of hierarchical systems

The systemic approach and the concept of structural levels (from Latin organizo — to put in order) form the methodological basis of modern biology. The term hierarchy (from Greek hieros — sacred and arche — power, rule) implies subordination: elements form a stepped series where lower levels are controlled by higher ones.

All levels of organization share basic features that distinguish living from non-living matter:

• Self-regulation.
• Self-renewal.
• Self-reproduction.

The most important feature of multilevel systems is the appearance of emergent properties. These are fundamentally new qualities that arise with the transition to each new level and are absent in isolated components of the system.

Main levels of organization of the living

Six basic stages in the development and functioning of living matter are distinguished:

1. Molecular. Consists of biological macromolecules (proteins, nucleic acids, and other biopolymers). This is where the most important life processes originate: energy transformation, metabolism, and the transfer of hereditary information.
2. Cellular. The cell represents the elementary genetic, structural, and functional unit of development for all organisms. At this stage, metabolism and information transfer continue.
3. Organismal. The unit is the individual organism, viewed in continuous development—from the moment of conception to death. In multicellular organisms, tissues, organs, and organ systems are formed at this level. Due to strict cell specialization, such organisms function in the environment more actively, productively, and steadily.
4. Population-species. This is a supra-organismal system. It includes a collection of organisms of the same species united by a common habitat (population) and panmixia. It is here that elementary evolutionary transformations take place.
5. Biogeocoenotic. A biogeocoenosis is a complex aggregate of organisms of various species and different levels of organization that are inextricably linked with the environmental factors of their habitat.
6. Biospheric. The aggregate of all biogeocoenoses on the planet. Within this global ecosystem, the cycling of substances and transformation of energy take place, driven by the activity of all organisms on Earth.

Levels of study of a multicellular organism

When studying multicellular objects, a more detailed classification is applied. It is based on the sizes of structures, the object itself, and the method by which this object is studied:

• Anatomical method (organismal and organ levels). Studies the organism as a whole and individual organs. The size of the objects is 0.1 mm (100 µm) or more.
• Histological or light-optical method (tissue level). Aimed at studying tissues. Structure sizes: from 100 to 10 µm.
• Cytological method (cellular level). The objects are prokaryotic and eukaryotic cells. Their sizes vary within 20–0.2 µm (or down to 200 nm).
• Ultrastructural or electron-microscopic method (subcellular level). Allows the study of individual cellular components ranging in size from 200 to 10 nm.
• Physicochemical method (macromolecular level). Studies biopolymers whose sizes are only 10–1 nm.

Evolutionary causes for the emergence of levels

The appearance of new structural levels is a regular consequence of evolution, reflecting the transition of living matter to a qualitatively new state. Interaction with the environment is present at every stage, but the higher the level, the more complex and efficient these interactions are.

Mathematical justification proves the clear advantages of hierarchical systems over non-hierarchical ones (with an equal number of initial components):

• They form and develop significantly faster.
• Elements within them are more controllable, as lower-level steps are controlled by higher-level ones.
• Systems possess high plasticity and resistance to external disturbances.

Mechanism of formation of a new level: As the size of the system grows and the number of its elements increases, the mechanisms of negative feedback inevitably begin to lag. Because of this, the efficiency of self-regulation drops sharply, stability decreases, and there is a risk of system destruction. There is an urgent need to increase controllability. The result is the formation of a new structural level, the main purpose of which is to accelerate the action of negative feedback loops.

On the scale of the entire biosphere, multilevel organization ensures the strict organization of the living, increases the efficiency of its functioning, and reduces disorder (entropy).

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of negative feedback lag during the growth of biological systems
• Specifics of emergent properties at the biogeocoenotic and biospheric levels
• Mathematical justification of the stability and plasticity of hierarchical systems
• Features of panmixia at the population-species level

Other topics in «Biology as a Science, Introduction to Biology»

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