Problem 7 - Biology: The Dynamic Science

Question

Which activity is a step in the ovarian cycle? a. FSH stimulates the pituitary to release \(\mathrm{GnRH}\). b. When FSH and LH levels fall, the corpus luteum shrinks and the uterine lining breaks down. c. Luteinizing hormone stimulates the uterus to make progesterone. d. Estrogen levels initially have a positive feedback effect on the pituitary, which is followed by higher estrogen levels causing negative feedback. e. A fully developed corpus luteum inhibits uterine lining growth.

Step-by-Step Solution

Answer

The correct answer is option (b): When FSH and LH levels fall, the corpus luteum shrinks, and the uterine lining breaks down.

Step 1: Identifying Wrong Answers

First, eliminate option (a) because FSH stimulates the ovarian follicles, not the pituitary gland, to release GnRH. Similarly, exclude option (c) since Luteinizing hormone does not stimulate the uterus to make progesterone; instead, it triggers ovulation and the development of the corpus luteum from the ruptured follicle in the ovaries. Lastly, discard option (e) because a fully developed corpus luteum actually encourages growth of the uterine lining by secreting hormones like progesterone, not inhibiting it.

Step 2: Selecting the Correct Answer

The valid options left are (b) and (d). Both of them represent steps in the female reproductive cycle, but only (b) When FSH and LH levels fall, the corpus luteum shrinks, and the uterine lining breaks down signifies a step exclusively in the ovarian cycle, where the corpus luteum’s shrinkage marks the beginning of menstruation. On the other hand, while option (d) is accurate, it pertains to feedback mechanisms in the menstrual cycle that interacts with the pituitary gland, not limited to the ovarian cycle.