Cladogram Worksheet Generator
Gives pupils a table of invented taxa, one outgroup and a set of characters, ticked where each taxon has them, and asks them to build the cladogram. The model is stated on the sheet: each character appeared once and was never lost, and the outgroup has none. Under that model the table decides the cladogram exactly when every branch point carries a character, and the page checks that before showing the answer. You can also leave one branch point undecided on purpose, to discuss what the data cannot tell you.
What this generator does
Makes cladogram practice with an answer that is right by construction and checked independently, with taxa that cannot be looked up and a stated model, so the reasoning is the only route to the answer.
How to use this tool
- Choose 3 to 8 taxa.
- Keep 'Only tables with exactly one possible cladogram' ticked for a single right answer; untick it for a table with one undecided branch point.
- Optionally include characters found in only one taxon, which pupils should learn to set aside.
- Press Make a character table, open the answer to check it, and print the table with drawing space and the answer page.
Understanding the controls
- Taxa in the ingroup
- 3 to 8, plus one outgroup that has none of the characters.
- Only one possible cladogram
- When ticked every branch point carries a character; when not, one is left bare and the answer shows a three-way split.
- Single-taxon characters
- Adds up to two characters found in one taxon only; they appear on that taxon's own branch.
- Paper and seed
- Paper size and density for printing; a seed rebuilds the same table while the generator is unchanged.
Worked examples
- Seed 'fossil', five taxa, with single-taxon characters
- Outgroup Primet. Striped tail and clawed toes: all five. Feathery antennae and two pairs of wings: Bolim, Enfor and Prax. Webbed feet: Bolim and Enfor. Long sticky tongue: Irrup and Opple. A pouch (Prax) and padded feet (Opple) belong to one taxon each. Groups: Bolim + Enfor inside Bolim + Enfor + Prax, beside Irrup + Opple — one cladogram fits.
Common use cases
- Practising cladograms from shared characters before using real data
- Showing why a character found in every taxon or only one tells you nothing about grouping
- Discussing a branch point the data cannot resolve
How this generator works
A random branching order is built by splitting the taxa into two groups again and again. Each group is given one or two invented characters (one group may be left bare on request), and the columns are shuffled. The table is then read back on its own: each character's ticks form a group, every pair of groups must be nested or separate, and the cladogram is the nesting of the groups. Exactly one cladogram fits when there are one fewer groups than taxa.
Randomness and fairness
Taxa, branching order and characters are drawn with the browser's cryptographically secure generator, or from one seeded draw when a seed is typed. Seeded tables are deterministic, not cryptographic.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- The taxa, characters and branching are invented. Real characters are lost, gained twice and misjudged, and real cladistics weighs conflicting characters; this model has none of that.
- A cladogram shows branching order only. The drawing's heights and slopes do not mean time, distance or amount of change.
- Characters are present or absent; there are no multi-state characters or molecular data.
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