Video Summary - What Makes Something Alive? The 7 Characteristics of Life

Scientific concepts / nature phenomena presented

Scientists use specific criteria to determine whether something qualifies as living.

Made of cells
- Cells are the basic living unit.
- Unicellular organisms (e.g., bacteria) vs. multicellular organisms (many specialized cells).
Organized structure
- Cells form tissues and organs that work together.
Growth and development
- Predictable changes over time.
- Examples: seed → sprout → mature plant; caterpillar → butterfly.
Reproduction
- Produces offspring and passes traits to the next generation.
Use energy
- Plants: photosynthesis to capture sunlight energy.
- Animals: energy from consuming other organisms.
Respond to the environment
- Examples: plants orient toward light; animals move away from danger; bacteria move toward food.
Maintain homeostasis
- Keeps internal conditions stable despite external changes.
- Examples: sweating/shivering; plant pores closing during drought.
- Often compared to a thermostat.

Fire
- Discussed as moving, growing, consuming fuel, and spreading/reproducing via new fires.
- Not alive because it:
  - is not made of cells
  - lacks organized structure
  - lacks homeostasis
Viruses
- Debated:
  - Can reproduce and evolve, but only by hijacking host cells.
- Many scientists consider them on the edge of life because they cannot sustain themselves independently.
Crystals
- Can grow by adding material.
- Not alive because they can’t reproduce to create new crystals with unique characteristics.
Robots
- Current robots are said to not be alive due to lacking cells and self-reproduction (future possibility suggested).