The Metric System
The metric system is an internationally agreed upon measurement system based on decimals or powers of 10. Scientists use a refined version called the International System of Units (abbreviated SI). In biology, you will often find a need to describe measurements of length, volume, mass, time, temperature or amount of substance.
Metric Units:
- length: meter (m)
- volume: liter (L)
- mass: gram (g)
- time: second (s)
- temperature: Celsius (°C)
- Kelvin (K) is a unit of thermodynamic temperature and is the SI unit. The Kelvin scale in the same as the Celsius or centigrade scale but offset by 273.16
- Biology uses Celsius predominantly because of the range in which organisms live.
- amount of substance: mole (mol)
- A mole is a number representing 6.022×1023 of something
- Just as a pair of shoes equals 2 shoes, a mole of shoes is 6.022×1023 shoes
- Just as a dozen eggs equals 12 eggs, a mole of eggs is 6.022×1023 eggs
| Metric prefixes in everyday use |
|||
|---|---|---|---|
| Prefix | Symbol | Scientific Notation | Factor |
| tera | T | 1012 | 1000000000000 |
| giga | G | 109 | 1000000000 |
| mega | M | 106 | 1000000 |
| kilo | k | 103 | 1000 |
| hecto | h | 102 | 100 |
| deca | da | 101 | 10 |
| BASE UNIT | (none) | 100 | 1 |
| deci | d | 10-1 | 0.1 |
| centi | c | 10-2 | 0.01 |
| milli | m | 10-3 | 0.001 |
| micro | μ | 10-6 | 0.000001 |
| nano | n | 10-9 | 0.000000001 |
| pico | p | 10-12 | 0.000000000001 |
| Basic SI Units | ||
|---|---|---|
| Measure | SI Unit | Symbol |
| length | meter | m |
| mass | kilogram | kg |
| time | second | s |
| temperature | Kelvin (Celsius is used in Biology) | K (°C) |
| quantity | mole | mol |
| current | Ampere | A |
| luminosity | candela | cd |
