The Scale of Life
Zoom continuously across orders of magnitude, from nanometre-scale viruses to the tallest trees.
The Scale of Life Knowledge file
Place viruses, cells, animals, and giant trees on one order-of-magnitude scale to see the enormous range of life's sizes.
At a glance
- Smallest
- About 30 nanometres
- Largest
- About 116 metres
- Range
- Nearly 4 billion times
- Scale
- Logarithmic
Core concepts
Each step may be ten times larger
A linear ruler cannot hold both viruses and giant trees. A logarithmic scale makes life across many orders of magnitude comparable.
Viruses are not cells
Viruses have no independent metabolism and must use host cells to reproduce; bacteria are cells that can live independently.
Size determines transport
Tiny cells can rely on diffusion, while larger organisms need circulatory, respiratory, and support systems to move materials around the body.
Ways to understand
- NanometresThe viral world
Most viruses are measured in nanometres, far below the resolution limit of ordinary light microscopes.
- MicrometresThe cellular world
Bacteria, yeast, and blood cells often fall in the micrometre range and are major subjects of microscopy.
- MetresMulticellular life
Specialized tissues and internal transport let animals and plants exceed the size limits of a single cell.
What to observe
- ObserveRemember reference objects
Use a hair's width, a red blood cell, or the human body as anchors for a realistic sense of scale.
- ObserveWatch the units change
Notice transitions among nanometres, micrometres, millimetres, and metres; every three metric prefixes usually represents a thousandfold change.
- ConsiderBigger does not mean more complex
A larger body does not necessarily imply a more complex genome or a more advanced form of life.