1. Organization: Living things are highly organized, with specialized structures (cells, tissues, organs) working together to perform complex functions.

2. Metabolism: Living things carry out chemical reactions (metabolism) to obtain and use energy. This includes breaking down food, building molecules, and eliminating waste.

3. Growth and Development: Living things increase in size and complexity over time. This can involve cell division and differentiation, leading to growth and the development of specialized structures.

4. Responsiveness: Living things react to stimuli in their environment. This includes responding to changes in light, temperature, chemicals, or physical contact.

5. Adaptation: Living things evolve over time, adapting to their environment. This means inheriting and passing on traits that make them better suited to their surroundings.

6. Reproduction: Living things produce offspring, ensuring the continuation of their species. Reproduction can be sexual (involving two parents) or asexual (involving a single parent).

It's important to note that some of these characteristics, like "growth" or "development", can be exhibited by non-living things under certain circumstances. However, the combination of all six characteristics in a system defines it as a living organism.