Question
▶️Answer/Explanation
- Human chorionic gonadotropin (HCG) is a hormone produced by the developing embryo (and later the placenta) soon after fertilization.
- Its primary role is to maintain the corpus luteum, which in turn continues to produce progesterone.
- Progesterone is essential to maintain the uterine lining and prevent menstruation, allowing the pregnancy to continue.
Why other options are incorrect:
B: Oxytocin, not HCG, stimulates uterine contractions at birth.
C: HCG promotes progesterone production; it does not inhibit it.
D: Polyspermy prevention is achieved by changes in the egg membrane after fertilization, not by HCG.
Question
The drawing shows a flower of red valerian, Centranthus ruber.
(a) State the name and function of structures I and II.
Structure I name and function: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Structure II name and function: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b) Structure III is the ovary. Outline the processes that occur in the ovary.
(c) Structure IV contains a gland that secretes a sugary liquid. Suggest a benefit to the plant of secreting this liquid.
Answer/Explanation
(a)
Structure I:
- Name: Stigma
- Function: Receives pollen during pollination; pollen grains land and are captured here.
Structure II:
- Name: Anther
- Function: Produces, contains, and releases pollen (male gametes).
(b)
- Meiosis occurs to produce female gametes (ovules).
- Fertilization happens: fusion of male and female gamete nuclei.
- The fertilized ovule develops into a seed.
- The ovary develops into a fruit.
(c)
- Attracts insects or animals (pollinators).
- Helps ensure pollination by encouraging pollinator visits.