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Biology 30 · Worksheets

Development · Set B

Ten questions of mixed difficulty, covering Development. Print it, or work through it on screen — the answer key starts on its own page.

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Development · Set B

Biology 30 · maddyhelps.com

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  1. Which hormone stimulates the uterus to contract during labour?

    1. a) prolactin
    2. b) insulin
    3. c) progesterone
    4. d) oxytocin

  2. Which germ layer forms the lining of the digestive tract?

    1. a) amnion
    2. b) ectoderm
    3. c) mesoderm
    4. d) endoderm

  3. Which germ layer develops into the nervous system and skin?

    1. a) ectoderm
    2. b) trophoblast
    3. c) endoderm
    4. d) mesoderm

  4. What does the inner cell mass of a blastocyst develop into?

    1. a) the amniotic fluid
    2. b) the corpus luteum
    3. c) the embryo
    4. d) the placenta only

  5. Why is the first trimester the most sensitive time for exposure to teratogens?

    1. a) The fetus is growing fastest in size
    2. b) The placenta is fully developed
    3. c) The major organs are forming during this time
    4. d) The fetus is already breathing

  6. A home pregnancy test detects which hormone?

    1. a) oxytocin
    2. b) estrogen
    3. c) hCG (human chorionic gonadotropin)
    4. d) FSH

  7. Why is labour described as an example of positive feedback?

    1. a) Oxytocin levels fall as contractions get stronger
    2. b) The body works to keep contractions at a steady level
    3. c) Contractions cause more oxytocin to be released, which causes stronger contractions until birth
    4. d) Contractions stop once progesterone rises

  8. Identical twins form when:

    1. a) two eggs are fertilized by two sperm
    2. b) one egg is fertilized by two sperm
    3. c) two zygotes fuse together
    4. d) one early embryo splits into two

  9. In early development, "cleavage" refers to:

    1. a) the formation of three germ layers
    2. b) the embryo attaching to the uterine wall
    3. c) rapid cell divisions of the zygote without the embryo growing in overall size
    4. d) the splitting of identical twins

  10. A teratogen is:

    1. a) a hormone that maintains pregnancy
    2. b) a substance, such as alcohol, that can cause birth defects
    3. c) an enzyme that helps sperm reach the egg
    4. d) a cell that becomes the placenta

Answer key · Development · Set B

Biology 30 · maddyhelps.com

  1. d) oxytocin — Oxytocin from the posterior pituitary drives contractions. Prolactin is for making milk.
  2. d) endoderm — Endo- means inner. The endoderm lines the digestive and respiratory tracts and forms organs like the liver and pancreas.
  3. a) ectoderm — Ecto- means outer: the outer layer becomes the skin and the nervous system. Mesoderm forms muscle and bone; endoderm forms the gut lining.
  4. c) the embryo — The inner cell mass becomes the embryo itself. The outer layer, the trophoblast, helps form the placenta. Those inner cells are the source of embryonic stem cells.
  5. c) The major organs are forming during this time — Organogenesis happens mostly in the first trimester, so interference then can affect how whole organs form. Later exposure more often affects growth.
  6. c) hCG (human chorionic gonadotropin) — hCG is made by the tissue around the early embryo once it implants, so its presence in urine signals pregnancy.
  7. c) Contractions cause more oxytocin to be released, which causes stronger contractions until birth — Positive feedback amplifies a change instead of reversing it. Each contraction pushes the baby against the cervix, triggering more oxytocin, until birth ends the loop.
  8. d) one early embryo splits into two — Identical twins come from one zygote, so they share the same DNA. Two eggs fertilized separately give fraternal twins, who are no more alike than other siblings.
  9. c) rapid cell divisions of the zygote without the embryo growing in overall size — During cleavage the cells divide by mitosis again and again, getting smaller each time, so the ball of cells stays about the size of the original egg.
  10. b) a substance, such as alcohol, that can cause birth defects — Teratogens cross the placenta and interfere with development. Alcohol, certain medications and some infections, such as rubella, are examples.