It's Alive
Examine characteristics of living things and how scientists identify life processes.
How can we determine whether something is living, once living, or nonliving based on observable characteristics?
Key Vocabulary
Organism
A living thing that carries out life processes.
Cell
The basic unit of structure and function in all living things.
Homeostasis
The ability of an organism to maintain stable internal conditions.
Metabolism
All chemical reactions in an organism that maintain life.
Stimulus
Something in the environment that causes a response in an organism.
Reproduction
The process by which organisms produce new organisms of the same kind.
Key Concepts
- 1
All living things share certain characteristics: they are made of cells, use energy, grow, reproduce, and respond to their environment.
- 2
Once-living things had these characteristics in the past but no longer carry out life processes.
- 3
Nonliving things have never had life characteristics.
- 4
Scientists classify things by carefully observing and testing for life processes.