Organogenesis and the Model Organisms That Made It Visible · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Fold, tube, branch, prune

Science · Organisms & Life Processes · ages 20-21
Name ______________________   Date ____________

  1. Which pair of structures develops from the vertebrate neural tube?

    • Finger bones and the limb's skeletal joints
    • The brain and spinal cord of the nervous system
    • The lungs and the muscles of the chest wall

  2. A sheet of cells folds around an inner space and its edges join. Which structure has formed?

    • A solid clump with no enclosed inner space
    • An open sheet whose borders remain apart
    • A hollow tube with joined borders

  3. In developing mouse limbs, apoptosis helps remove cells between digits so the digits can separate.

    Circle one:   True   False

  4. You want repeated live images of a heart forming in one zebrafish embryo. Which listed strength best serves that task?

    • A large adult body for measuring changes in adult mass
    • A long generation time for observing slow breeding cycles
    • An embryo clear enough for repeated live imaging

  5. A growing lung airway bud extends and splits repeatedly. What change does branching produce?

    • More airway branches and growing tips
    • A flat sheet with no remaining airway branches
    • Fewer airway branches as the growing tips fuse

  6. A lab plans a large Drosophila genetic screen for changes in fly development. Which pair of strengths best supports the screen?

    • Large adult bodies and a long interval between generations
    • Short generations and tools for changing genes
    • Opaque early embryos and few tools for studying gene function

  7. At the same developmental stage, mutant mouse limbs retain webbing and show fewer cells undergoing apoptosis there than controls. Which conclusion is supported?

    • Extra cell division is established as the cause because the limbs retain webbing.
    • The observations prove reduced cell death is the sole cause of retained webbing.
    • Reduced cell death may contribute, but other processes could also be involved.

  8. A mechanism is found in zebrafish heart formation. A lab claims it must act identically in human hearts. What is the strongest objection?

    • One species does not establish an identical mechanism in humans
    • Transparency makes findings unsuitable for comparison with other species
    • Differences between fish and mammals rule out all shared developmental mechanisms
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Answer key

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

Fold, tube, branch, prune W1-mt_MXqKNdT519-s1

  1. The brain and spinal cord of the nervous system · The neural tube is an embryonic structure that develops into the brain and spinal cord.
  2. A hollow tube with joined borders · The joined edges close the folded sheet around an inner space, forming a hollow tube.
  3. True · Apoptosis contributes to removal of cells between developing mouse digits, helping them separate.
  4. An embryo clear enough for repeated live imaging · The task requires optical access to the developing heart over time. Adult size and generation time address different experimental needs.
  5. More airway branches and growing tips · Repeated branching produces additional airway branches and growing tips. It does not by itself explain development of the gas-exchange surface.
  6. Short generations and tools for changing genes · A large genetic screen tests developmental effects of many gene changes. Genetic tools and short generations support that work.
  7. Reduced cell death may contribute, but other processes could also be involved. · The observations support reduced cell death as a possible contributor. They do not establish increased cell division or prove that cell death is the sole cause.
  8. One species does not establish an identical mechanism in humans · Developmental mechanisms can be shared across species, but their roles and timing can differ. A zebrafish result alone does not establish identical action in humans.
Worksheet · LightMySky