BSc 1407 MB Ch. 46: Animal Reproduction

Activity: Human Gametogenesis 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.

Scientific Thinking: What Is Causing Delayed Puberty in a Female Patient? Part B - Testing hypotheses The patient's doctor decided to put the patient on estrogen therapy for five months. Supplemental estrogen would be expected to correct some of the potential problems in estrogen signaling identified in Part A. This would allow estrogen signaling to go forward. Unfortunately, after five months, the patient still showed no signs of puberty. Based on this result, which of the hypotheses from Part A can you now eliminate? Select all that apply.

- Estrogen level too low - Estrogen molecule is structurally defective

Identify the role(s) of follicle-stimulating hormone (FSH) in human reproduction.

- FSH stimulates the growth of new follicles in the ovary. - FSH promotes the activity of Sertoli cells, which nourish sperm developing within seminiferous tubules

Scientific Thinking: What Is Causing Delayed Puberty in a Female Patient? Part A - Developing hypotheses In young women, the hormone estrogen is essential for normal development. At puberty, estrogen triggers the development of female features such as a higher-pitched voice, smaller body size, breasts, and wider hips.Estrogen is a lipid-soluble, steroid hormone. The diagram below shows the estrogen signaling process that normally functions in the body. Next to the diagram is a list of some possible causes for this young woman's delayed puberty. Evaluate each possible cause based on what you know about the woman's symptoms and the estrogen signaling pathway. Drag a check mark next to those causes that are consistent with what you know so far. Drag an "X" next to those causes that are not likely because they are inconsistent with what's known.

- Likely (check mark) - NOT Likely (X) - Likely (check mark) - Likely (check mark) - Likely (check mark) - Likely (check mark)

Activity: Human Reproduction Part G Which of the following events occurs at the onset of the luteal phase of the menstrual cycle?

Development of the corpus luteum.

Activity: Human Gametogenesis Part G How does spermatogenesis differ from oogenesis?

Diploid cells give rise to four functional gametes in spermatogenesis.

Activity: Reproductive System of the Human Male Part E Which pituitary secretion stimulates sperm production?

FSH

Activity: Human Gametogenesis 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

Activity: Human Gametogenesis Part C What products are formed when a diploid cell undergoes meiosis?

Four haploid cells

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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).

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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.

Activity: Reproductive System of the Human Male Part F Which pituitary secretion stimulates the testes to secrete androgens?

LH

Interpreting Data: Female Reproductive Cycle Hormones Part C A surge in which hormone(s) immediately precedes ovulation?

LH and FSH

Activity: Human Reproduction Part D Which hormone spikes midway through the menstrual cycle and triggers ovulation?

Luteinizing hormone (LH).

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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.

What is the fundamental difference between male and female vertebrates?

Males produce many, motile gametes and females produce few, stationary gametes.

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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.

Interpreting Data: Female Reproductive Cycle Hormones Part F A surge in estradiol levels correlates with a surge in progesterone levels.

Not supported

Which hormone's secretion is controlled by a positive feedback mechanism?

Oxytocin

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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.

Activity: Human Reproduction Part A Which characteristic of the male reproductive system is not variable among animal species that reproduce sexually?

Presence of genitalia.

Activity: Human Reproduction Part C Which function is not performed by the male reproductive system?

Production and storage of oogonia.

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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.

Select the correct statement about reproduction and eukaryotic life cycles.

Some animal adults are haploid.

Activity: Human Gametogenesis Part E Which diploid cells are produced by an embryonic germ cell?

Spermatogonia.

What is the "twofold" cost of sex?

The higher number of female offspring produced by an asexual female

Activity: Human Gametogenesis Part B What role do germ cells play in gametogenesis?

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

Activity: Human Gametogenesis Part A True or false? Humans form gametes by a process called gametogenesis.

True

Activity: Human Reproduction Part B True or false? The basic functions of the human female reproductive system are to produce eggs, develop offspring, and make hormones.

True

Activity: Reproductive System of the Human Male 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

Sex Hormones and Mammalian Reproduction 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: - testosterone - development offacial hair - increasedaggressiveness - increased muscle mass - deepening of voice estrogens and progesterone: - fat depositionin hips - changes in calcium metabolism - breast development - estradiol - increased waterretention neither: ---------

Building Vocabulary: Word Roots - Animal Reproduction and Development Part B

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

Sex Hormones and Mammalian Reproduction 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 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. - The low dose of estradiol in the combination pill prevents the surge in LH production.

Activity: Reproductive System of the Human Female Part G Ovulation usually occurs on or about day _____ of a 28-day ovarian cycle.

14

Interpreting Data: Female Reproductive Cycle Hormones Part E The levels of pituitary hormones never increase above 10 grams/L of blood.

Cannot be determined from the graph

Activity: Human Reproduction Part F Where does a human fetus develop?

Uterus

Activity: Human Reproduction Part E Which male reproductive structures are responsible for the transport and delivery of sperm?

Vas deferens, urethra, and penis.

Sex Hormones and Mammalian Reproduction 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

Scientific Thinking: What Is Causing Delayed Puberty in a Female Patient? Part C - Interpreting data Review each experiment and identify which of the three hypotheses under consideration it tested. Then decide whether the data support or refute (fail to support) that hypothesis. Drag the appropriate labels under each column in the data table.

a. Hypothesis 3 b. Hypothesis 1 c. Hypothesis 2 d. refute e. support f. refute

Interpreting Data: Female Reproductive Cycle Hormones Part A What does the x-axis of this graph represent?

days since the start of the last cycle

Activity: Reproductive System of the Human Male Part A Sperm become capable of movement while in the _____.

epididymis

Interpreting Data: Female Reproductive Cycle Hormones Part D Based on the graph, elevated levels of which hormone(s) most likely stimulate the LH/FSH surge just before ovulation?

estradiol

Activity: Reproductive System of the Human Female 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

Activity: Reproductive System of the Human Female Part C After ovulation, high levels of _____ inhibit _____ secretion.

estrogen and progesterone ... FSH and LH

Activity: Reproductive System of the Human Female Part D Developing ovarian follicles primarily secrete _____.

estrogens

Scientific Skills Exercise: Making Inferences and Designing an Experiment 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

Activity: Reproductive System of the Human Female Part E If there is fertilization, secretion of _____ by the early embryo maintains the corpus luteum.

human chorionic gonadotropin

Interpreting Data: Female Reproductive Cycle Hormones Part B What does the y-axis in the top panel represent?

levels of pituitary hormones

Activity: Reproductive System of the Human Female Part B A rapid increase in the _____ level stimulates ovulation.

luteinizing hormone

Building Vocabulary: Word Roots - Animal Reproduction and Development Part A

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

Activity: Reproductive System of the Human Male Part C The secretion of androgens is regulated by a _____ feedback mechanism involving the _____ and _____.

negative ... hypothalamus ... pituitary gland

Activity: Reproductive System of the Human Female Part H What is the usual site of the fertilization of an egg cell?

oviduct

Activity: Reproductive System of the Human Male Part G Sperm develop in the _____.

seminiferous tubules

Activity: Reproductive System of the Human Male Part B Sperm exit a male's body via the _____.

urethra

Activity: Reproductive System of the Human Female Part A A fertilized egg usually implants itself and develops in the _____.

uterus