- With each step upward in the biological hierarchy, new properties emerge that were not present at the simpler organizational levels.
- Life is difficult to define because it is associated with numerous emergent properties that reflect a hierarchy of structural organization.
- An organism is a living whole greater than the sum of its parts.
- For example, a cell dismantled to its chemical ingredients is no longer a cell.
- Has been a powerful strategy in biology.
- For example, Watson and Crick deduced the role of DNA in inheritance by studying its molecular structure.
Some of the emergent properties and processes associated with life are:
1. Order. Organisms are highly ordered, and other characteristics of life emerge from this complex organization.
2. Reproduction. Organisms reproduce; life comes only from life (biogenesis).
3. Growth and Development. Heritable programs stored in DNA direct the species-specific pattern of growth and development.
4. Energy Utilization. Organisms take in and transform energy to do work, including the maintenance of their ordered state.
5. Response to Environment. Organisms respond to stimuli from their environment.
6. Homeostasis. Organisms regulate their internal environment to maintain a steady-state, even in the face of a fluctuating external environment.
7. Evolutionary Adaptation. Life evolves in response to interactions between organisms and their environment.
Because properties of life emerge from complex organization, it is impossible to fully explain a higher level of order by breaking it into its parts.
Holism = The principle that a higher level of order cannot be meaningfully explained by examining component parts in isolation.
It is also difficult to analyze a complex process without taking it apart.
Reductionism = The principle that complex system can be understood by studying its component parts.
The study of biology balances the reductionist strategy with the goal of understanding how the parts of cells, organisms and populations are functionally integrated.
