What it does
A dichotomous key names a living thing by asking a chain of questions that each have only two answers, yes or no (“dichotomous” means “cut in two”). Each answer sends you to the next question until only one name is left. Scientists use keys to identify plants, insects and fish in the field.
This page has eight animals drawn simply: an earthworm, a spider, a butterfly, a fish, a frog, a snake, a pigeon and a cat.
- Follow a key: tap an animal (or press Random mystery), look at its drawing, and answer each question. The key is shown as a tree with your route highlighted. If you answer wrongly, the page tells you which question went astray.
- Build a key: start with all eight animals. Pick a question; the page splits the group into “yes” and “no”. Keep splitting the first group that still has more than one animal. Questions that don’t split a group are refused, with the reason. When every animal stands alone, press Follow my key to test it.
It follows the Class 9 science chapter Patterns in Life: Diversity and Classification and the Class 11 biology chapter The Living World. Where these animals sit in the big tree of life is in classification tree, and a key for any group of organisms, written as text, is in dichotomous key builder.
How to use it
- Follow a key: pick the mystery animal, then press Yes or No for each question.
- Read the result. Tap another animal to start again.
- Build a key: choose a question from the list and press Use this question. Use Undo or Start again as you like.
- When it’s finished, compare your longest route with the ready-made key, then press Follow my key.
A worked example
Mystery: the snake. Backbone? Yes. Feathers? No. Fur? No. Legs? No. Fins? No. The key says snake, in 5 questions. The pigeon takes only 2 (backbone yes, feathers yes).
Now build: “Does it have a backbone?” splits the eight into five with backbones and three without. “Does it have legs?” then splits the five into frog, pigeon, cat and fish, snake.
Tips
- Good questions are about things you can see for sure (wings, legs), not size or colour, which vary.
- A question that splits a group in half makes a shorter key.
- Every route must end at one name only.
FAQ
Is a spider an insect? No. Insects have six legs; spiders have eight, which is why the key asks.
Is this the NCERT book? No. It covers the same topic with fibub’s own drawings. fibub is not part of NCERT.
Where the numbers come from
- Dichotomous keys and the features used (backbone, legs, wings, feathers, fur, fins, scales, number of legs, moist skin) are standard school biology. The animals are fibub's own simple drawings; the key and text were written for fibub.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.