D3.1 Reproduction

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: A

A. Correct. HCG is secreted by the embryo (trophoblast) shortly after implantation. It maintains the corpus luteum, which continues to secrete progesterone, essential to maintain the uterine lining and support early pregnancy.

B. Incorrect. HCG is not involved in labor; oxytocin is the hormone responsible for uterine contractions.

C. Incorrect. After the first trimester, the placenta itself produces progesterone. HCG is primarily important in early pregnancy.

D. Incorrect. HCG primarily maintains progesterone via the corpus luteum; estrogen is also produced, but progesterone maintenance is its main role.

Which step occurs in both spermatogenesis and oogenesis?

A. First division of meiosis is stopped in prophase I until puberty begins.

B. Germinal epithelium cells divide by mitosis.

C. At the end of the first division in meiosis, the cytoplasm is divided equally between daughter cells.

D. Four haploid gametes are produced at the end of meiosis II.

Answer: B

A. Incorrect. First division of meiosis stops only in oogenesis, not in spermatogenesis, where meiosis proceeds continuously after puberty.

Correct. In both spermatogenesis and oogenesis, germinal epithelium cells divide by mitosis to maintain the germ cell population and produce cells that will enter meiosis

Incorrect. Cytoplasm divides equally only in spermatogenesis, but in oogenesis, cytoplasm division is unequal, producing a large secondary oocyte and a small polar body.

Incorrect. Four haploid gametes are produced only in spermatogenesis; in oogenesis, only one functional ovum is produced along with polar bodies.

What is a similarity between the testes of males and the ovaries of females in humans?

A. They produce gametes throughout the life of the individual.

B. They secrete hormones into the blood stream.

C. Their development is controlled by a gene on the Y chromosome.

D. They release products to the outside of the body directly through the urethra.

Answer: B

A. Incorrect. Testes produce sperm continuously after puberty, but ovaries produce a finite number of eggs, so this is not a similarity.

B. Correct. Both testes and ovaries are endocrine organs that secrete hormones (testosterone in males, estrogen and progesterone in females) into the bloodstream, regulating sexual development and reproductive functions.

C. Incorrect. Only test development is influenced by the SRY gene on the Y chromosome; ovaries develop without it.

D. Incorrect. Only male sperm can exit via the urethra; ovum is released into the oviduct, not directly outside

What is a function of luteinizing hormone (LH) in the female menstrual cycle?

A. To promote secondary sexual characteristics

B. To inhibit progesterone secretion

C. To stimulate the follicle to release estrogen

D. To trigger ovulation

Answer: D

A. Incorrect. Secondary sexual characteristics are mainly stimulated by estrogen, not LH.

B. Incorrect. LH does not inhibit progesterone; in fact, after ovulation, it helps form the corpus luteum, which secretes progesterone.

C. Incorrect. FSH, not LH, primarily stimulates estrogen production by the developing follicle.

D. Correct. A surge of LH mid-cycle induces ovulation, causing the mature egg to be released from the follicle into the oviduct.

A female is overweight, feels cold and tired, and often fails to ovulate during the menstrual cycle. Which two hormones are probably secreted at insufficient levels?

A. Estrogen and FSH

B. LH and thyroxin

C. Insulin and glucagon

D. Epinephrine and leptin

Answer: B

A. Incorrect. While estrogen and FSH are important for ovulation, in this context the symptoms of fatigue, feeling cold, and overweight point toward hypothyroidism, which involves low thyroxin, rather than solely reproductive hormones.

B. Correct. Low thyroxin from underactive thyroid can cause fatigue, feeling cold, and weight gain, while insufficient LH prevents ovulation, explaining the menstrual irregularity.

C. Incorrect. Insulin and glucagon regulate blood glucose, not ovulation or thyroid-related metabolism.

D. Incorrect. Epinephrine and leptin affect stress response and appetite, not directly ovulation or thyroid function.

What is an example of negative feedback in the menstrual cycle?

A. High levels of estrogen inhibit FSH secretion.

B. High levels of LH stop progesterone secretion.

C. High levels of FSH delay ovulation.

D. High levels of progesterone make follicles less receptive to FSH.

Answer: A

A. Correct. Rising estrogen levels from developing follicles signal the pituitary gland to reduce FSH secretion, preventing overstimulation of multiple follicles.

B. Incorrect. LH triggers ovulation and supports formation of the corpus luteum, which secretes progesterone; it does not inhibit progesterone.

C. Incorrect. FSH stimulates follicle growth; high FSH does not delay ovulation.

D. Incorrect. While progesterone prepares the endometrium and can indirectly influence follicle responsiveness, the direct negative feedback mechanism in the menstrual cycle is primarily estrogen inhibiting FSH.

If seeds of an unknown species of plant are discovered, what assumption can be made about the species?

A. Its male gametes are contained within pollen.

B. Its seeds are contained within fruits.

C. It is in the domain archaea.

D. It is in the phylum angiospermophyta.

Answer: A

A. Correct. The presence of seeds indicates the plant is a seed plant. In all seed plants, male gametes are carried in pollen, which fertilizes the ovule.

B. Incorrect. Only angiosperms (flowering plants) have seeds enclosed in fruits. Seed plants also include gymnosperms, whose seeds are not enclosed in fruits.

C. Incorrect. Archaea are prokaryotes; they do not produce seeds.

D. Incorrect. While some seed plants are angiosperms, seeds are also found in gymnosperms, so this cannot be assumed just from the presence of seeds.

Successful sexual reproduction in flowering plants depends on several essential processes. Outline the role of pollination and seed dispersal. [2]

Pollination: transfer/dispersal/movement of pollen from anther/stamen to stigma OR transfer/dispersal/movement of pollen between plants/flowers prior to/allowing fertilization

Seed dispersal: strategy of distribution of seeds so that new plants have space/nutrients to develop/avoid competition/colonize new habitats 

Sample answer: 

Pollination is the transfer of pollen from the anther (stamen) to the stigma, either within a flower or between flowers, allowing fertilization to occur [1]. Seed dispersal is the distribution of seeds away from the parent plant, ensuring that new plants have space, access to nutrients, and the opportunity to colonize new habitats [1].

Hormones are distributed throughout the body by the blood. Outline the roles of two reproductive hormones during the menstrual cycle in women. [2]

Two of the following:

a. FSH/follicle-stimulating hormone stimulates the development of follicles/follicle cell division in the ovary to produce eggs

b. LH/luteinizing hormone triggers ovulation/development of the corpus luteum

c. estrogen stimulates development of the uterine lining/endometrium

d. progesterone maintains the uterine lining/endometrium OR inhibits other hormones by negative feedback, e.g., FSH

e. HCG stimulates ovary to produce progesterone in early pregnancy

f. other verifiable hormone and roles relevant to the menstrual cycle

Sample answer:

FSH stimulates the development of ovarian follicles and promotes egg maturation in the ovary [1]. LH triggers ovulation and stimulates the formation of the corpus luteum [1].

Describe the genetic and hormonal control of male sexual characteristics in a human. [3]

Three of the following:

a. male if Y chromosomes present

b. gene on Y chromosome/SRY promotes development of testes from embryonic gonads

c. testes secrete testosterone

d. testosterone stimulates sperm production/spermatogenesis

e. testosterone stimulates development in fetus of male genitals/primary sexual characteristics

f. testosterone stimulates development of male secondary sexual characteristics OR testosterone causes changes to become adult male during puberty

Sample answer:

An individual develops as male if both X and Y chromosomes are present [1]. The SRY gene on the Y chromosome promotes the development of testes from embryonic gonads [1]. The testes then secrete testosterone [1], which stimulates sperm production (spermatogenesis) [1] and promotes the development of male genitals and primary sexual characteristics in the fetus [1]. During puberty, testosterone also stimulates the development of male secondary sexual characteristics, causing the individual to develop adult male features [1].