Biology / Unit 1: The Science of Biology and Chemistry of Life
1.1 Characteristics of Life
Notes
Biology is the study of life. Scientists use a set of shared traits to decide whether something is alive.
- Living things are made of one or more cells.
- They use energy (metabolism), grow and develop, and reproduce.
- They respond to stimuli and maintain stable internal conditions, called homeostasis.
- They have DNA as their genetic material, and populations evolve over time.
- Something must show all of these traits to be considered alive; a single trait (like growth) is not enough.
Practice
Which trait describes your body keeping its temperature near 37°C on a cold day?
Homeostasis is keeping internal conditions stable when the outside changes.
Crystals of salt can grow larger in a salty solution. Why are they NOT considered alive?
Growth alone is not enough; living things show all the characteristics of life.
A plant bends toward a sunny window. Which characteristic of life does this show?
Light is a stimulus, and bending toward it is a response.
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