Classification Keys
Explore and use classification keys to identify, group, and name living things in local and wider environments
What a learner can do afterwards
- Follow a branching classification key to identify an unknown organism
- Choose clear separating questions and check or repair a proposed yes/no classification key for six to eight organisms
- Use a key to identify organisms in the local environment during a field activity
1 · Read
You have grouped living things by their features. A classification key helps identify something from a stated set. In a yes/no key, start at the first question. Check the feature and follow the matching branch to another question or a name. Follow only the questions on that route.
Zara's key lists a snail, slug, spider and ground beetle. Legs? No leads to Shell? Yes names snail; no names slug. Zara sees no legs and a shell, so her route ends at snail. Check every question on your route. A guessed name does not replace an answer.
To build a yes/no key for six to eight cards, compare their features. Choose a clear question that separates the cards still together. The groups need not be equal. 'Is it big?' needs a size limit; 'Is its body longer than 2 cm?' gives one. Repeat for each group that still has several cards.
Check a whole key by tracing each card and matching its endpoint name. Six cards: pigeon, spider, adult butterfly, wingless worker ant, snail, slug. Legs? No: shell? Yes names snail; no names slug. Legs? Yes: feathers? Yes names pigeon. No feathers: six legs? No names spider. Six legs: wings? Yes names butterfly; no names worker ant. Swap any misplaced names, then test again.
To trace a name backward, find the answer branch ending at that name. Follow its connections back to the start. Then read the answers in starting order. For worker ant, that order is yes to legs, no to feathers, yes to six legs and no to wings.
This is one route. Other answers can lead to other questions.
Test every listed creature from the start. If two cards need different names but reach one endpoint, add a separating question. A creature outside the list may need another key. Outdoors, choose a key for that place and kind of living thing. Observe without disturbing it. If a feature is hidden, ask an adult for help instead of guessing.
Check that both answer groups add to the total. Equal groups are allowed: share ten cards between two groups, giving five to each. Unequal groups work too. To find a missing group, subtract the known group from the total. For twelve cards with five yes answers, twelve minus five leaves seven no answers.
Check the feature and follow its branch. A useful yes/no key separates its listed creatures and leads each route to a name.
The lesson, questions and flashcards were written for this dataset.
The readings and flashcards were written for this dataset.
More to read
Pick a suitable key
Before using a key, read what it covers. A key for woodland plants will not identify every pond animal. The place and the kinds of living things both matter.
Start at the first question. Observe the feature it names and follow the matching branch. Stop when that route reaches a name. Questions on other branches do not need answers for this route.
If your find is outside the key's list, look for a more suitable key or ask for help. Reaching an endpoint does not prove that an unlisted creature has that name.
Check every card
Build a key with six to eight named creature cards. Record clear features on each card. Choose a yes/no question that separates the cards into groups. The groups may have different sizes.
Choose another question for each group that still contains several cards. Continue until each route reaches the intended name.
Now test every card from the beginning. A question that gives every remaining card the same answer does not separate that group. If two cards need different names but reach one endpoint, add a question about a feature they do not share.
When a feature is hard to see
A key may ask about a feature that is hidden. You might see the top of a leaf but not its underside. That does not tell you whether hairs are present underneath.
Keep the answer undecided until you can observe clearly. Ask an adult for help. Avoid damaging plants or disturbing animals to answer a question.
Describe what you observed, not what you guessed. If you can see a feature clearly, compare it with the key's wording. If the question uses a measurement, use its stated limit rather than deciding what big or small means to you.
2 · Watch
En anglaisTake it off screen
Where it sits
Learn first
Optional connections
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
24 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.