What are living things?

Living things (organisms) share seven defining characteristics that distinguish them from non-living matter:

1. Organization: Made of cells; ordered complex structures from molecular to organism level
2. Metabolism: Carry out chemical reactions to obtain and use energy
3. Growth and development: Increase in size and complexity following a genetic blueprint
4. Response to stimuli: Detect and respond to environmental changes (plants turning toward light, humans pulling from heat)
5. Reproduction Produce offspring (sexually or asexually)
6. Homeostasis: Regulate internal conditions (temperature, pH, fluid balance)
7. Heredity: Pass genetic information to offspring via DNA

Categories of living things (Domains of Life):

• Bacteria: single-celled prokaryotes (no nucleus)
• Archaea: single-celled prokaryotes, often in extreme environments
• Eukarya: Protists, Fungi, Plants, and Animals (all have cells with a nucleus)

Note on viruses: they replicate but have no metabolism of their own their status as "living" is still debated.