Living systems do not simply exist within their environments. They continuously interact with them in ways that affect their ability to remain alive and function effectively.
This is why some conditions matter to organisms while others do not.
A plant requires water, light, nutrients, and suitable temperatures. A bacterium requires access to energy sources and favourable chemical conditions. An animal depends upon food, shelter, and protection from injury or predation. These conditions are not important because an external observer declares them important. They are important because they influence whether the organism can maintain itself over time.
APS describes this capacity through the concepts of viability and organised persistence.
Viability refers to the ability of a living system to continue functioning under changing conditions. A viable organism remains within the range of conditions necessary for its ongoing activity.
Organised persistence refers to the dynamic continuity of a living system despite constant change. Organisms continuously replace materials, repair damage, regulate internal processes, and respond to environmental challenges while maintaining their overall organization.
Because living systems are organized around maintaining viability and organised persistence, some environmental differences become consequential. Water availability matters to a plant. Nutrient concentrations matter to a bacterium. A predator matters to a deer. These conditions affect whether the organism can continue its activities and maintain its organization.
In APS, this is the foundation of biological meaning. Something becomes biologically meaningful when it makes a difference to the viability and organised persistence of a living system.
The significance is therefore neither arbitrary nor externally imposed. It emerges from the ongoing relationship between organisms and the conditions that support or threaten their continued existence.