Characteristics of living organisms

All living organisms share eight characteristics that separate them from non-living matter:

• Nutrition
• Respiration
• Excretion
• Sensitivity
• Movement
• Homeostasis (control of internal conditions)
• Reproduction
• Growth and development

Every organism — from the smallest bacterium to the largest whale — must display all eight of these processes to be classified as alive. Showing only some of the characteristics, as fire or crystals do, is not sufficient.

Each characteristic reflects an essential biological function:

Nutrition

• Provides the raw materials and energy the organism needs for its other life processes.

Respiration

• Releases that energy from nutrient molecules within the cells.

Excretion

• Removes toxic waste products of metabolism from the organism.

Homeostasis

• Maintains the stable internal environment (controlled internal conditions) that cells need to function.

Sensitivity

• Allows organisms to detect and react to stimuli, which are changes in their surroundings.

Movement

• Enables a change in position or place by the organism or part of it.

Reproduction

• Ensures the continuation of the species by making more of the same kind of organism.

Growth and development

• Allow organisms to increase in size and complexity over time.