Building a Phylogeny: Homology, Shared Derived Characters and Parsimony · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Crown the tree with fewest edits

Science · Genetics & Evolution · ages 19-21
Name ______________________   Date ____________
  1. One tree needs 5 edits and its rival needs 8. How many does the winner need?

    Answer: ______________

  2. Which trait carries shared blood information?

    • Wing shapes of fliers and crawlers
    • Forelimb bones of mammals
    • Sweetness of every candy
  3. The tree with the fewest required changes wins.

    Circle one:   True   False

  4. What makes a group complete and valid?

    • An ancestor with some kids cut out
    • A random pile of species
    • An ancestor plus all its kids
  5. A trait sits in every species studied. What is its grouping power?

    • It cannot define a group
    • It defines the tightest group
    • It doubles the evidence
  6. A friend groups mammals by backbones. Is that sound?

    • Yes, backbones mark mammals
    • No, far more than mammals own one
    • Yes, old traits group best
  7. A friend groups birds with bugs by wings. Is that right?

    • Yes, looks never lie
    • Yes, function proves blood
    • No, they evolved apart despite looking alike
  8. Every candy in the jar is sweet. What does sweetness group?

    • Nothing, it groups no one
    • It marks the tightest team
    • It roots the whole tree
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Crown the tree with fewest edits W1-mt_GFmiVZ8g-F-s1

  1. 5 · The smaller tally wins, so five edits beats eight and the winner needs five.
  2. Forelimb bones of mammals · Mammal forelimbs share build from shared blood, while flier wings arose apart.
  3. True · Each extra origin is an extra unobserved event, so fewer is better.
  4. An ancestor plus all its kids · Valid groups are complete: nothing left out and nothing extra added.
  5. It cannot define a group · Old states fit any subgrouping, so only fresh shared states mark true subgroups.
  6. No, far more than mammals own one · Hair is fresh at that level, while backbones spread far wider.
  7. No, they evolved apart despite looking alike · Flier wings in birds and bugs are the classic apart by looks trap.
  8. Nothing, it groups no one · A trait in every piece mirrors old shared states: consistent with everything, proving nothing.
Worksheet · LightMySky