Key learning points

1. Most animals and plants are made up of millions or billions of cells.
2. Cell numbers can be expressed in standard form.
3. Cells are usually too small to see with the unaided eye.
4. Comparison of sizes of eukaryotic and prokaryotic cells, and cell structures, in µm, nm, and in metres in standard form.

Common misconception

Keywords

• Million - 1 000 000, or one thousand thousand, or 10⁶.

• Billion - 1 000 000 000 or one thousand million, or 10⁹.

• Standard form - A way of writing down very large or very small numbers easily; e.g. 1000 = 10³.

• Micrometre (µm) - One millionth of a metre, or 1 m / 1 000 000, or 1 × 10⁻⁶ m.

• Magnification - Making small objects appear larger in order to see more detail.