CH 46 Hw

Part A - Hormones and secondary sex characteristics Sex hormones, including androgens, estrogens, and progesterone, are produced by the gonads in males and females and control the development of primary sex characteristics—the structures directly involved in reproduction. The sex hormones also trigger the development of secondary sex characteristics—the physical and behavioral characteristics that appear during puberty that are not directly related to reproduction. Because the principal sex hormones differ in males and females, different secondary sex characteristics develop. Sort the following secondary sex characteristics and hormones based on whether they are related to androgens, estrogens and progesterone, or neither. Drag each phrase to the appropriate bin.

Androgens: increased muscle mass, testosterone, deepening of voice, increased aggressiveness, development of facial hair Estrogens and progesterone: estradiol, increased water retention, changes in calcium metabolism, fat deposition in hips, breast development Neither: blank

Part D Which of the following statements about oogenesis in humans is true?

Beginning at puberty, a primary oocyte completes its first meiotic division to form a secondary oocyte and a polar body approximately every month.

Part G How does spermatogenesis differ from oogenesis?

Diploid cells give rise to four functional gametes in spermatogenesis.

Part E Which pituitary secretion stimulates sperm production?

FSH

Part F True or false? The production of sperm begins at puberty when spermatogonia undergo meiosis I to form primary spermatocytes, which then undergo meiosis II to form secondary spermatocytes. These secondary spermatocytes go on to form spermatids, which mature into sperm cells.

False

Part C What products are formed when a diploid cell undergoes meiosis?

Four haploid cells.

Part C - Interpreting the data From Jost's results, what can you infer about the role of the gonads in controlling the development of mammalian genitalia?

In the absence of a signal from the male gonads, all embryos develop as female, regardless of whether they are genetically male (XY) or female (XX).

Part B Normally, the gonads of a developing embryo produce hormones during development. How did Jost block this process?

Jost removed the portion of each embryo that would form the gonads.

Part F Which pituitary secretion stimulates the testes to secrete androgens?

LH

Part G You test the hypothesis that the development of male genitalia normally requires testosterone from the embryonic gonads. You do this by removing the gonads of male (XY) embryos and replacing them with a crystal of testosterone. Which of the following results would support your hypothesis?

Male genitalia develop in the rabbits.

Part E - Making a prediction What result would Jost have obtained if both male and female genital development required signals from the gonads?

None of the embryos that had surgery would have developed normal, sexually differentiated genitalia.

Part D - Eliminating alternative hypotheses The data in Jost's experiment could be explained if some aspect of surgery other than gonad removal caused female genitalia to develop. If you were to repeat Jost's experiment, how might you test the validity of this alternative hypothesis?

Perform a sham surgery on some embryos. For example, open the embryo but do not remove the gonads.

Part F - Designing a follow-up experiment Jost's experiment showed that the development of male genitalia requires some signal from the male gonads during embryonic development. But is this signal a hormone? To test the hypothesis that the signal is the hormone testosterone, which of the following experiments should you perform?

Remove the embryonic gonads and replace them with another source of testosterone.

Part E Which diploid cells are produced by an embryonic germ cell?

Spermatogonia.

Part C - Preventing pregnancy Some methods of contraception, such as birth control pills and patches, use synthetic hormones to manipulate the ovarian cycle in females. Some hormone-based contraceptives contain a combination of a synthetic estradiol and a synthetic progestin (progesterone-like hormone). Other hormone-based contraceptives contain progestin only. Which statements correctly explain how the hormone-based contraceptives affect the female reproductive cycle? Select all that apply.

The low dose of estradiol in the combination pill prevents the surge in LH production. The low doses of progestin and estradiol in the combination pill have a negative feedback effect on the hypothalamus, blocking ovulation. The progestin in the progestin-only pill causes changes in the endometrium that prevent implantation.

Part B What role do germ cells play in gametogenesis?

They produce cells that divide by mitosis and then undergo meiosis to form gametes.

Part A True or false? Humans form gametes by a process called gametogenesis.

True

Part B - Hormonal control of the ovarian cycle in humans Hormones control the two closely linked reproductive cycles in human females—the uterine (or menstrual) cycle and the ovarian cycle. During one uterine cycle, which is approximately 28 days long, the lining of the uterus undergoes hormonally-regulated changes, if no pregnancy has occurred. At the same time, the hormones also cause a series of changes to take place in an ovary, known as the ovarian cycle. The flowchart below describes the events of the ovarian cycle. Drag the names of the hormones to their appropriate locations on the flowchart, starting with the release of a hormone from the hypothalamus. Labels may be used once, more than once, or not at all. (Note: GnRH = gonadotropin-releasing hormone; LH = luteinizing hormone; FSH = follicle-stimulating hormone.)

a. GnRH b. LH and FSH c. estradiol d.LH and FSH e. estradiol and progesterone f. LH and FSH g. estradiol and progesterone

Part D Which hormone(s) is(are) directly responsible for triggering the development of the secondary sex characteristics of males, such as beard growth?

androgens

Part A Animals utilizing external fertilization are typically _____.

aquatic animals

Part A Sperm become capable of movement while in the _____.

epididymis

Part F If there is no fertilization, degeneration of the corpus luteum results in a drop in _____, which results in the sloughing off of the uterus's endometrium.

estrogen and progesterone

Part C After ovulation, high levels of _____ inhibit _____ secretion.

estrogen and progesterone ... FSH and LH

Part D Developing ovarian follicles primarily secrete _____.

estrogens

Part A Can you match these prefixes, suffixes, and word roots with their definitions?

female: gyn seed: sperm bud, precursor: blast to produce: -gen- stomach: gastr- male: andro egg: oo- (or ov-) before: pro- (or pre-) top, highest: acro-

Part A - Understanding the experimental design In this experiment, scientists inferred how something works normally based on what happened when the normal process was blocked. What normal process was blocked in Jost's experiment?

hormone production by the embryo's gonads during development

Part E If there is fertilization, secretion of _____ by the early embryo maintains the corpus luteum.

human chorionic gonadotropin

Part B A rapid increase in the _____ level stimulates ovulation.

luteinizing hormone

Part C The secretion of androgens is regulated by a _____ feedback mechanism involving the _____ and _____.

negative ... hypothalamus ... pituitary gland

Part H What is the usual site of the fertilization of an egg cell?

oviduct

Part A The anatomical location for the typical union of a sperm and an egg (conception) is the _____.

oviducts

Part A Which of the following correctly traces the path of sperm from their site of production to their exit from a man's body?

seminiferous tubule → epididymis → vas deferens → urethra

Part G Sperm develop in the _____.

seminiferous tubules

Part A Salamander and insect populations consisting only of genetically identical females lack males because _____.

sperm do not fuse with eggs during reproduction, but the eggs develop into embryos anyway

Part B Sperm exit a male's body via the _____.

urethra

Part A A fertilized egg usually implants itself and develops in the _____.

uterus

Part B Can you match these prefixes, suffixes, and word roots with their definitions?

witness: test- with or together with: co- against: contra- half: semi- middle: meso- first: prim- front: antero- behind: post- (or postero-)

Part G Ovulation usually occurs on or about day _____ of a 28-day ovarian cycle.

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