Gastrulation and Laying Down the Body Axes · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Folding a ball into a body

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

  1. Which adult tissues come from ectoderm?

    • Muscle and bone
    • Gut lining and liver
    • Skin and the nervous system

  2. What kind of change drives gastrulation?

    • Rapid cell division
    • Cells moving and folding
    • Cells shrinking away

  3. The heart ends up left and the liver right. When was that decided?

    • When axes were laid down in the early embryo
    • At birth
    • When organs start working

  4. An organiser graft grows a second body axis nearby. Why did the experiment need an ungrafted control?

    • To keep the embryo alive
    • To count the cells
    • To prove the graft, not the wound, directed the new axis

  5. A dye marks mesoderm cells in an early embryo. Where will marked cells end up?

    • In skin and nerves
    • In muscle, bone, or blood
    • In the gut lining

  6. Before gastrulation the embryo is a ball with no inside. What does it have right after?

    • An inside, an outside, and three layers
    • A full set of organs
    • A head and limbs

  7. A student claims axes form by cells dividing faster at the head end. What is wrong?

    • Heads form before axes
    • Axes are set by cells moving to places, not by extra division
    • Division never happens in embryos

  8. Endoderm, the outer layer, makes skin and nerves.

    Circle one:   True   False

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Answer key

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

Folding a ball into a body W1-mt_PABfw_4RPs-s1

  1. Skin and the nervous system · The outer layer makes skin and the nervous system.
  2. Cells moving and folding · Gastrulation is cells crawling, folding, and squeezing to new places.
  3. When axes were laid down in the early embryo · The head to tail, back to belly, and left right map is set while the embryo is tiny.
  4. To prove the graft, not the wound, directed the new axis · Only the control shows the wound alone cannot organise an axis.
  5. In muscle, bone, or blood · Mesoderm, the middle layer, builds muscle, bone, blood, and kidneys.
  6. An inside, an outside, and three layers · Movement delivers an inside, an outside, and three layers, but no organs yet.
  7. Axes are set by cells moving to places, not by extra division · Axes are mapped by moving cells, with division in the back seat.
  8. False · Ectoderm is the outer layer and makes skin and nerves; endoderm is inside.
Worksheet · LightMySky