IB Biology HL (HIGHER level)- 2024 – Practice Questions- All Topics
Topic 11.4 Sexual reproduction
Topic 11 Weightage : 8%
All Questions for Topic 11.4 – Gametogenesis, Reproductive Tissue, Egg and Sperm, Animal Fertilization, Human Fertilization, Embryo Development, Human Chorionic Gonadotropin, Placenta, Birth Process, Gestation Periods, Semen Production, Amniotic Sac
Question
The pregnancy test for humans is based on detection of the hormone HCG. What is the reason for detection of this hormone indicating pregnancy?
A HCG is involved in milk production.
B HCG production is blocked by negative feedback during menstruation.
C HCG is produced by an embryo.
D HCG is released during the acrosome reaction.
▶️Answer/Explanation
Ans: C
The correct answer is C. HCG is produced by an embryo. HCG, or human chorionic gonadotropin, is a hormone that is produced by the cells that form the placenta. It is detectable in the blood and urine of pregnant women and is used as a marker for pregnancy. HCG production begins shortly after fertilization and continues to increase throughout the first trimester of pregnancy. Therefore, the detection of this hormone indicates the presence of an embryo and confirms pregnancy.
The diagram shows the female reproductive system.
Which structures do K and L identify?
▶️Answer/Explanation
Markscheme
B
K is placenta, an organ that develops in the uterus during pregnancy. It provides oxygen and nutrients to the developing fetus and removes waste products. The placenta is usually located on the upper or posterior (back) wall of the uterus.
L is endometrium, the inner lining of the uterus that thickens during the menstrual cycle to prepare for a possible pregnancy. If pregnancy does not occur, the endometrium is shed during menstruation. The endometrium is located inside the uterus.
What helps to prevent polyspermy?
A. The unequal division of oocytes
B. The placental barrier
C. The contraceptive pill
D. The cortical reaction
▶️Answer/Explanation
Markscheme
D
D. The cortical reaction helps to prevent polyspermy. The cortical reaction is a process that occurs in the egg after fertilization, where cortical granules are released from the egg and form a fertilization envelope that prevents other sperm from penetrating the egg.
What does the blastocyst secrete?
A. HCG
B. Estrogen
C. ADH
D. Progesterone
▶️Answer/Explanation
Markscheme
A
A. The blastocyst secretes human chorionic gonadotropin (HCG), which is a hormone that helps to maintain the corpus luteum during early pregnancy. The corpus luteum produces progesterone, which is necessary for the maintenance of the endometrial lining and the prevention of menstruation during pregnancy.
The diagram shows the exchange processes that take place in the placenta between the maternal and fetal blood. Which process requires endocytosis?
▶️Answer/Explanation
Markscheme
D
The cells separating maternal and fetal blood form the placental barrier. This must be selectively permeable, allowing some substances to pass, but not others
Exchange process in the placenta can be summarized as:
Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma cells (white blood cells). Thus, process D requires endocytosis.
Which hormone is inhibited during pregnancy in order to prevent contractions of the uterus?
A. Oxytocin
B. Progesterone
C. Estrogen
D. FSH
▶️Answer/Explanation
Markscheme
A
A. Oxytocin is inhibited during pregnancy in order to prevent contractions of the uterus. Progesterone, which is produced by the corpus luteum, helps to maintain the endometrial lining and prevent contractions of the uterus during pregnancy. Oxytocin is a hormone that stimulates uterine contractions during labor and is inhibited during pregnancy to prevent premature contractions.
Question
What is the role of HCG in pregnancy?
A. It is secreted by the embryo to stimulate progesterone secretion by the ovary during early pregnancy.
B. Together with oxytocin, it is involved in the positive feedback required for uterine contractions during birth.
C. It sustains the secretion of progesterone by the placenta throughout pregnancy.
D. It stimulates the ovary to maintain secretion of estrogen in early pregnancy.
▶️Answer/Explanation
Ans:B
B is the correct answer because HCG, together with oxytocin, is involved in the positive feedback required for uterine contractions during birth. HCG is secreted by the placenta and helps to stimulate the production of estrogen and progesterone during early pregnancy. Oxytocin is a hormone that is involved in the contraction of the uterus during labor and delivery. The positive feedback loop between HCG and oxytocin helps to ensure that the contractions are strong enough to push the baby out.