Animal Body Plans: Symmetry, Cavities and the Deep Splits · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Sorting animals by their embryos

Science · Organisms & Life Processes · ages 19-20
Name ______________________   Date ____________

  1. A jellyfish builds its body from two germ layers. What does that make it?

    • Monoblastic
    • Triploblastic
    • Diploblastic

  2. A new animal has mirror left and right halves. What symmetry is that?

    • Radial
    • Bilateral
    • None

  3. In a deuterostome embryo, what does the first opening become?

    • The anus
    • The mouth
    • The coelom

  4. An unfamiliar worm has three tissue layers and a true fluid filled cavity. What follows?

    • It must be a jellyfish
    • It has no muscles
    • It belongs with the complex bilaterians

  5. A round slow animal is found on the seabed. Its embryo first opening becomes the anus. Where does it belong?

    • With the deuterostomes, by its embryo
    • With the clams, by its looks
    • Outside the animals, for lack of symmetry

  6. Two unrelated sea animals share a streamlined shape. How do you place them?

    • By adult shape alone
    • By shared embryo features on the tree
    • By speed in water

  7. A student insists two streamlined swimmers must be close kin. What is the best reply?

    • Streamlining can evolve twice under the same pressures, so check embryo traits
    • Fast swimmers always share a recent ancestor
    • Body cavities decide swimming speed

  8. A sea urchin is a closer relative of a clam than of a fish, since all three are sea animals.

    Circle one:   True   False

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Answer key

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

Sorting animals by their embryos W1-mt_hEC72cvFQF-s1

  1. Diploblastic · Two layered builders like jellyfish are diploblastic.
  2. Bilateral · One midline making two mirror halves is bilateral symmetry.
  3. The anus · Deuterostome means the first opening becomes the anus, with the mouth later.
  4. It belongs with the complex bilaterians · Three layers plus a true coelom mark the complex bilaterian grade.
  5. With the deuterostomes, by its embryo · The embryo split outranks the round slow looks.
  6. By shared embryo features on the tree · Shared pressures can sculpt one shape twice, so embryo traits decide.
  7. Streamlining can evolve twice under the same pressures, so check embryo traits · Convergence explains shared shape without shared recent ancestry.
  8. False · The urchin embryo marks it a deuterostome, nearer to fish than to clams.
Worksheet · LightMySky