1. Organization: Living things are highly organized, meaning they are composed of one or more cells, the basic unit of life. These cells are organized into tissues, organs, and organ systems, working together to maintain the organism's life.
2. Metabolism: All living things carry out chemical reactions that sustain life. This includes processes like:
* Anabolism: Building complex molecules from simpler ones (e.g., photosynthesis)
* Catabolism: Breaking down complex molecules into simpler ones (e.g., cellular respiration)
3. Growth and Development: Living things increase in size (growth) and change over time (development). This is driven by the processes of metabolism and cell division.
4. Responsiveness (Irritability): Living things can detect and respond to stimuli in their environment. This can be anything from changes in light or temperature to the presence of food or danger.
5. Reproduction: Living things can create new individuals, either sexually (involving the combination of genetic material from two parents) or asexually (involving only one parent). This ensures the continuation of the species.
6. Adaptation: Living things evolve over time, developing traits that help them survive and reproduce in their environment. This is a gradual process driven by natural selection.
7. Homeostasis: Living things maintain a relatively stable internal environment, even when external conditions change. This is crucial for survival and is achieved through various regulatory mechanisms.
These seven characteristics are not simply a checklist; they are interconnected and fundamental to the very definition of life. While some exceptions may exist, these characteristics provide a comprehensive understanding of what distinguishes living organisms from non-living matter.
