Basic Concepts
In a nutshell: Living things grow, reproduce, use energy, respond to their environment, and maintain balance inside their bodies.
## What Makes Something Alive?
Living things, or organisms, share a set of features that make them different from nonliving things. These features include the ability to grow, reproduce, respond to stimuli, use energy, and maintain homeostasis (a stable internal environment). Whether it's a towering tree or a tiny bacterium, all living things have these characteristics!
### Key Features
- **Growth and Development:** Organisms grow and often change shape or form as they mature.
- **Reproduction:** Living things create new organisms like themselves, either sexually or asexually.
- **Response to Environment:** Organisms can sense and react to changes, like plants bending toward light.
- **Energy Use:** All living things need energy, which they get from food or sunlight.
- **Homeostasis:** Organisms maintain balance inside their bodies, like keeping a constant temperature.
## Why Does it Matter?
Understanding what makes something alive helps scientists study life on Earth and search for life beyond our planet.
Examples
- A sunflower grows taller and turns toward the sun.
- A cat runs away when it hears a loud noise.
Key terms
- Homeostasis
- The ability of an organism to keep its internal environment stable.
- Stimulus
- A change in the environment that causes a response.