# Biological Criteria for Life ## The Eight Biological Criteria for Life 1. **Order:** All living things have a highly organized structure and are composed of at least one cell. 2. **Use of Energy:** All living things take in energy and transform it to do many different kinds of work - Example: Plants use sunlight to create sugars which are converted into [[Bioenergetics]] 3. **Reproduction:** All living things are able to reproduce their own kind through sexual or asexual means. - "Life only comes from life" - (Biogenesis) 4. **Growth & Development:** Heritable programs in the form of DNA direct the pattern of growth and development, which results in an organism that has the characteristics of a particular species. 5. **Response to Stimuli:** All living things have the ability to respond to an environmental stimulus such as temperature, amount of light, availability of water, or the actions of other living things. 6. **Homeostasis:** The ability to maintain and regulate a tolerable internal environment (feedback loops) when the external environment fluctuates - Examples: - Maintaining a constant body temperature (Too Cold -> Shivering; Too Hot -> Sweating) - Blood Pressure - Glucose Levels 7. **Adaptation:** The process by which a species becomes fitted to its environment through evolution ([[Natural Selection]]) 8. **Evolution:** A change in the genetic composition of a population over successive generations.