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2.6 The Nature of Life
summary
Physics of Life
- Although living systems obey the laws of physics and chemistry, the notion of function or purpose differentiates biology from other natural sciences.
- Organisms exist to reproduce, whereas rocks and stars have no purpose. Selection for function has produced the living cell with a unique set of properties that distinguish it from inanimate systems of interacting molecules.
- Cells exist far from thermal equilibrium by harvesting energy from their environment.
- They are composed of thousands of different types of molecules. They contain information for their survival and reproduction in the form of their DNA.
Processes of Life
- Homeostasis: regulation of the internal environment to maintain a constant state
- Organization: structural composition of one or more cells — the basic units of life
- Metabolism: transformation of energy to maintain internal organization and do work
- Growth: A growing organism increases in size and organization of its parts through developmental processes
- Adaptation: the ability to change over time in response to the environment
- Response to stimuli: ranging from reactions of a unicellular organism to external chemicals to complex reactions involving all the senses of multicellular organisms
- Reproduction: the ability to produce new individual organisms
- All these processes have underlying physical and chemical bases, and these lifeforms adapt life to physical, ecological and social environments, via sensory, signaling, and control mechanisms, which use energy.
Information Usage Logic
- All biological life is based on function or purpose, and at the higher levels of emergence, intention. Information use at each level of a logical hierarchy is based on contextually informed logical choices of the form:
{GIVEN CONTEXT C, IF T(X) THEN F1(Y), ELSE F2(Z)}
where T(X), F1(Y) and F2(Z) are arbitrary functions of variables X, Y, Z, including logical operations (AND, OR, NOT, NOR, etc).