Levels of complexity in biological systems

- extended to include thought as a psychological component of behaviour.

Main theme :- Inter-related / interacting components at different levels of complexity

Noosphere = "realm" of thought, in which evolution can also occur (as well as in biosphere)

Biosphere = set of interacting ecosystems (can be subdivided into BIOMES)
Ecosystem = set of interacting communities and their abiotic environment
Community = set of interacting populations (i.e. more than onespecies)
Population = set of interacting individual organisms (i.e. a single species); interactions determining population behaviour can thus be: intraspecific (individuals of same species affecting each other) or interspecific (individuals of different species)

Organism = set of interacting organs / organ systems

Organ = set of interacting tissues, coordinated to perform a biological function
Tissue = set of interacting cells, specialised for their roles in the tissue
Cell = set of interacting organelles and sub-cellular structures
Sub-cellular organelles = set of interacting molecules forming coherent structures with definite functions

Molecule = set of interacting atoms
Atom = set of interacting fundamental particles
Fundamental particle = ?

YOU, as an individual organism are situated about halfway up this hierarchy. What you do, because of the patterns of interactions, has a definite effect on the overall functioning of the biosphere, i.e. on the global or planetary ecosystem. Your existence depends upon a "satisfactory" interaction with your environment (i.e. everything and everyone outside you), including your behaviour.

Increasing complexity of systems at higher levels in this hierarchy; correspondingly poorer degrees of scientific understanding.

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