DP Biology (first assessment 2025)

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Question 23M.2.HL.TZ1.6c

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Date May 2023 Marks available [Maximum mark: 7] Reference code 23M.2.HL.TZ1.6c
Level HL Paper 2 Time zone TZ1
Command term Describe Question number c Adapted from N/A
c.
[Maximum mark: 7]
23M.2.HL.TZ1.6c
(c)

Describe the hormone feedback mechanisms that help to prepare a woman’s body for pregnancy, sustain the pregnancy and then give birth.

[7]

Markscheme

Preparing the woman’s body for pregnancy

a. FSH stimulates estrogen secretion (by the developing follicle);
b. estrogen increases FSH receptors so boosting estrogen production/so causing positive feedback;
c. estrogen stimulates repair/thickening of the endometrium/uterus lining;
d. high levels of estrogen stimulate LH production/inhibit FSH secretion (negative feedback);
e. LH (surge/peak) stimulates ovulation;

Sustaining pregnancy

f. LH stimulates the development of corpus luteum / corpus luteum secretes progesterone;
g. progesterone inhibits FSH/LH secretion (negative feedback);
h. progesterone maintains lining of uterus/endometrium (for pregnancy/implant of embryo);
i. progesterone inhibits uterine contractions;
j. HCG (secreted by embryo) stimulates maintenance of corpus luteum;

Childbirth

k. oxytocin stimulates uterine/myometrial contractions which stimulate oxytocin secretion;
l. positive feedback (mechanism used to stimulate childbirth);

Syllabus sections