1. Organization:
* Living organisms are highly organized: They consist of cells, the basic units of life, and often complex systems within those cells. Non-living things lack this level of internal organization.
2. Metabolism:
* Living organisms have metabolism: They carry out chemical reactions that allow them to acquire and use energy, build and break down molecules, and maintain their internal environments. Non-living things don't have this metabolic machinery.
3. Growth and Development:
* Living organisms grow and develop: They increase in size and complexity over time, often following a specific pattern. Non-living things don't grow or develop in this way.
4. Reproduction:
* Living organisms reproduce: They create new individuals, passing on their genetic information. Non-living things do not reproduce themselves.
5. Response to Stimuli:
* Living organisms respond to their environments: They react to changes in light, temperature, chemicals, and other stimuli. Non-living things may react to stimuli, but not in the same way as living things.
6. Homeostasis:
* Living organisms maintain homeostasis: They regulate their internal conditions (like temperature and pH) to stay within a narrow range, even when the external environment changes. Non-living things don't have this internal control.
7. Adaptation and Evolution:
* Living organisms evolve over time: Their populations change in response to their environment, becoming better suited to their surroundings. Non-living things do not evolve in this way.
Important Note: While these characteristics are generally useful in distinguishing living from non-living things, there are some edge cases. For instance, viruses are complex, but lack some of the defining traits of living things. This raises questions about the boundaries of life itself.
Ultimately, understanding the complex interactions of these characteristics helps us define what it means to be alive.
