Earth holds an enormous variety of life. See how scientists organise that diversity into a nested hierarchy, and explore the five kingdoms of living things.
Earth holds a huge variety of life forms and ways of living. To make sense of this diversity, scientists group organisms based on shared features into a classification scheme — a nested hierarchy, much like sorting everyday objects into groups and subgroups based on shared similarities.
Scientists use a binomial (two-part) naming system, developed by the Swedish scientist Carl Linnaeus, in which every species gets a unique two-word Latin name (genus + species). Latin is used because it's a "dead" language that doesn't change meaning over time, giving every scientist in the world — regardless of their home language — the same, stable name for a species.
One widely-used classification system divides all living organisms into five kingdoms. A key distinction across these kingdoms is between prokaryotes (cells with no nucleus, e.g. Monera/Bacteria) and eukaryotes (cells with a true nucleus — all other kingdoms).
As scientific knowledge grows, classification systems continue to change and improve — the five-kingdom system is one of several currently accepted approaches, not a final, unchangeable truth.
Click a kingdom to see its defining features and examples.
| Organism | Cells | True nucleus? | Cell wall? | How it obtains food |
|---|---|---|---|---|
| P | Many cells | Yes | No | Ingests and digests food inside its body |
| Q | One cell | No | Yes | Absorbs simple nutrients directly from surroundings |
| R | Many cells | Yes | Yes (cellulose) | Makes its own food by photosynthesis |
| S | Many cells | Yes | Yes (chitin) | Absorbs nutrients externally by decomposing dead matter |