1. In mammals, sex is determined by the presence of XX (homozygous) in males and XY (heterozygous) in females, while in birds, sex is determined by the presence of ZZ (homozygous) in females and ZW (heterozygous) in males.
2. In mammals, sex is determined by the presence of XX (homozygous) in males and XY (heterozygous) in females, while in birds, sex is determined by the presence of ZW (heterozygous) in females and ZZ (homozygous) in males.
3. In mammals, sex is determined by the presence of XX (homozygous) in females and XY (heterozygous) in males, while in birds, sex is determined by the presence of ZZ (homozygous) in females and ZW (heterozygous) in males.
4. In mammals, sex is determined by the presence of XX (homozygous) in females and XY (heterozygous) in males, while in birds, sex is determined by the presence of ZW (heterozygous) in females and ZZ (homozygous) in males.

In sexual reproduction, two cells of a species combine to form another cell. Why is this useful?

1. It produces new combination of genes, which enables offspring to survive during environmental changes.
2. It results in the production of many offspring in a short period of time.
3. It does not involve gamete formation and needs less energy.
4. It allows immobile organisms to reproduce in the absence of a mate.

1. LH and FSH are produced in the ovaries, and estradiol and progesterone are produced in the pituitary.
2. Estradiol and progesterone secreted from the corpus luteum cause the myometrium to thicken.
3. Progesterone is produced by the corpus luteum.
4. Secretion of GnRH by the hypothalamus is inhibited by high levels of estradiol, but stimulated by low levels of estradiol.

1. FSH
2. LH
3. inhibin
4. estrogen

What is the nature of the oogonium and the secondary oocyte? Which process results in the formation of the secondary oocyte?

1. A diploid oogonium forms a haploid oocyte by the process of mitosis.
2. A haploid oogonium forms a diploid oocyte by the process of meiosis.
3. A diploid oogonium forms a haploid oocyte by the process of meiosis.
4. A haploid oogonium forms a haploid oocyte by the process of meiosis.

What process increases the genetic diversity of diploid zygotes, allowing new combinations of alleles on chromosomes?

1. Their chromosome numbers are not the same.
2. The size of the sperm produced is different.
3. Some sperm may have a tail, whereas others may not.
4. Crossing over occurs during spermatogenesis.

The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following mechanisms shows negative feedback by the reproductive system in mammals?

1. Increasing levels of testosterone inhibit the production of GnRH, LH, and FSH by the hypothalamus and pituitary.
2. LH and FSH stimulate the interstitial cells of Leydig to release testosterone.
3. The growing follicle starts releasing estrogen in increasing amounts.
4. The corpus luteum releases progesterone after ovulation.

What are the positive feedback mechanisms by LH and FSH during the follicular and ovulation phase of the ovarian cycle?

1. The stimulation of the anterior pituitary by GnRH causes it to secrete the hormones LH and FSH. The increasing amounts of these hormones stimulate several follicles in the ovary to start growing to be released.
2. The stimulation of the anterior pituitary by GnRH causes it to secrete the hormone LH only. The increasing amounts of this hormone stimulate several follicles in the ovary to start growing, but only one of these matures to release the egg.
3. The stimulation of the anterior pituitary by GnRH triggers the secretion of the hormones LH and FSH. The increasing amounts of these hormones stimulate several follicles in the ovary to start growing, but only one of these matures to release the egg.
4. The stimulation of the anterior pituitary by GnRH causes it to secrete the hormones LH and TSH. The increasing amounts of these hormones stimulate a single follicle in the ovary to start growing.

Describe the possible event that would occur if the corpus luteum did not produce increasing amounts of progesterone.

1. The implanted zygote will not be able to derive enough nutrition from the endometrium.
2. Even if fertilization is successful, the zygote may not be able to implant successfully. If it does manage to implant, it will not be able to derive enough nutrition from the myometrium.
3. Even if fertilization is successful, the zygote may not be able to implant successfully. If it does manage to implant, it will not be able to derive enough nutrition from the endometrium.
4. The contraction of the uterus during childbirth and lactation will not take place, causing problems and complications in the mother.

What does a female contraceptive pill that inhibits the release of GnRH from the hypothalamus do?

1. reduce the secretion of FSH and LH from the anterior pituitary gland
2. initiate ovulation
3. increase the flow phase of the menstrual cycle
4. increase the production of estrogen and progesterone by the ovaries

What do the rising levels of FSH and LH in the follicular phase cause?

1. The follicles on the surface of the ovary start growing in preparation for ovulation.
2. The endometrium starts to thicken.
3. The corpus luteum starts secreting progesterone.
4. One of the mature follicles bursts, releasing the egg.

A couple has been trying to conceive for some time and goes to an endocrinologist for advice. If the endocrinologist diagnoses an obstruction in the oviducts of the female, what type of treatment can she recommend?

1. opting for in vivo fertilization or ligation of the fallopian tubes surgically so that the tubes are sealed
2. opting for in vivo fertilization or surgical removal of the fallopian tubes
3. opting for in vitro fertilization or ligation of the fallopian tubes surgically so that the tubes are opened
4. opting for in vitro fertilization or removal of the obstruction surgically and then rejoin of the ends of the fallopian tubes

How does a reproductive hormone that is secreted directly from the anterior pituitary stimulate the reproductive organs to produce hormones?

1. by traveling through the blood to reach the target organs
2. by binding with proteins to reach the reproductive organs
3. by sending a chemical messenger to activate the reproductive organs
4. by converting into an active form before targeting the reproductive organs

Explain the mechanisms by which hormones from the brain and ovaries interact, eventually leading to menstruation.

1. After the release of the egg from the follicle, the corpus luteum is formed, which inhibits FSH and LH production, which then inhibits GnRH production, causing no other follicle to develop. When no fertilization takes place, the corpus luteum degenerates and the progesterone level declines, initiating the breakdown of the myometrium and the start of the menstrual cycle.
2. After the release of the egg from the follicle, the corpus luteum is formed, which inhibits FSH and LH production, which then inhibits GnRH production, causing no other follicle to develop. When no fertilization takes place, the corpus luteum degenerates and the progesterone level declines, initiating the breakdown of the endometrium and the start of the menstrual cycle.
3. After the release of the egg from the follicle, the corpus luteum is formed, which inhibits FSH and LH production, which then facilitates GnRH production, causing no other follicle to develop. When no fertilization takes place, the corpus luteum degenerates and the progesterone level declines, initiating the breakdown of the endometrium and the start of the menstrual cycle.
4. After the release of the egg from the follicle, the corpus luteum is formed, which inhibits FSH and LH production, which then inhibits GnRH production, causing no other follicle to develop. When no fertilization takes place, the corpus luteum degenerates and the progesterone level rises, initiating the breakdown of the endometrium and the start of the menstrual cycle.

Multiple hormones work together to coordinate the female reproductive cycle. Which of these hormones is also responsible for the development of female secondary sexual characteristics, including breast development and hip widening?

1. estrogen
2. progesterone
3. follicle stimulating hormone
4. luteinizing hormone

Which hormone is released by the anterior pituitary as a part of the positive feedback loop between it and the ovary?

1. progesterone
2. GnRH
3. LH
4. estradiol

How does the feedback mechanism of hormones lead to muscular contractions during labor?

1. A feedback relay occurs between the uterus, hypothalamus, and posterior pituitary to assure an adequate supply of oxytocin, which causes the contraction of smooth muscles of the uterus, leading to the birth of the baby.
2. The posterior pituitary continuously produces oxytocin, which is sufficient for muscular contraction in the uterus, thereby causing the birth of the baby.
3. A feedback relay occurs between the uterus, hypothalamus, and posterior pituitary to assure an adequate supply of prolactin, which causes the contraction of the smooth muscles of the uterus, leading to the birth of the baby.
4. A feedback relay occurs between the uterus, hypothalamus, and posterior pituitary to assure an adequate supply of progesterone, which causes the contraction of the smooth muscles of the uterus, leading to the birth of the baby.

During childbirth, the hormone oxytocin causes contraction of the uterine wall muscles. As muscular contractions increase, more oxytocin is released from the pituitary, leading to more contractions. This is an example of which mechanism?

1. end product inhibition
2. negative feedback mechanism
3. positive feedback mechanism
4. feedback inhibition