Lesson 17_GRQs_Reproduction Part 2

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BIOL 101: Guided Reading Questions (GRQs) Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment L17 GRQs: Human Reproduction II Reading objectives:  Compare and contrast the processes of oogenesis and spermatogenesis and locations where they occur in the human body.  Describe what happens during the pre-ovulation and post-ovulation relative to hormones of the hypothalamus, pituitary and ovaries, and how these correspond to menstruation and ovulation.  Link the structures of the sperm to its functions. Module 27.5: The formation of sperm and egg cells requires meiosis Spermatogenesis 1. What is the name of the tubules within the testes that sperm develop in? seminiferous tubules. 2. How long does sperm formation take? around 64 to 72 days. 3. How are both mitosis and meiosis involved in making sperm? Mitosis occurs during the early stages of spermatogenesis, where spermatogonia (sperm stem cells) undergo mitotic division to produce more spermatogonia. Meiosis occurs later in spermatogenesis, specifically during the formation of sperm cells (spermatocytes). Meiosis involves two rounds of cell division (meiosis I and meiosis II) and results in the production of haploid sperm cells with half the number of chromosomes as the original spermatocytes. Oogenesis 1. What phase of meiosis are primary oocytes stopped short in at birth? prophase I of meiosis at birth 2. Ovaries typically produce their first secondary oocyte at what age? age of 11 to 14 in females. 3. What stage is the egg at when ovulation occurs? metaphase II of meiosis 4. Summarize Figure 27.5B for yourself: being sure to capture both the anatomical changes and the developing egg. Figure 27.5B illustrates the process of ovulation. Anatomically, it depicts the mature ovarian follicle, which has enlarged and is protruding from the ovary surface due to follicular growth. The developing egg, or secondary oocyte, is within the follicle. At ovulation, the follicle ruptures, releasing the secondary oocyte along with surrounding follicular fluid and cumulus cells into the fallopian tube. 5. Compare and contrast oogenesis and spermatogenesis:  Oogenesis : o Occurs in females. o Begins before birth and completes at menopause. o Results in the production of one functional egg and several polar bodies during each cycle. o Yields larger, non-motile gametes.

BIOL 101: Guided Reading Questions (GRQs) Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment o Unequal cytokinesis during meiosis, resulting in one large egg cell and three polar bodies. o Oocytes are arrested in prophase I until puberty. o Oocytes are not continuously produced throughout life.  Spermatogenesis : o Occurs in males. o Starts at puberty and continues throughout life. o Results in the production of four functional sperm cells from each spermatocyte. o Produces smaller, motile gametes. o Equal cytokinesis during meiosis, resulting in four equal-sized sperm cells. o Spermatogonia continually undergo mitosis to replenish the stem cell pool. o Continuous production of sperm occurs throughout reproductive years. Module 27.6: Hormones synchronize cyclic changes in the ovary and uterus 1. Briefly describe what is meant by the pre-ovulatory and the post-ovulatory phase: Pre-ovulatory phase : This phase occurs before ovulation and involves follicular development in the ovary. It is characterized by rising levels of estrogen, which stimulate the thickening of the uterine lining (endometrium) in preparation for potential implantation of a fertilized egg. Post-ovulatory phase : This phase occurs after ovulation and involves the release of the egg from the ovarian follicle. It is characterized by the formation of the corpus luteum, which secretes progesterone. Progesterone prepares the endometrium for implantation and helps maintain the uterine lining. 2. Describe the hormonal events before ovulation, be sure to include any positive or negative feedback discussed: Hormonal events before ovulation : Before ovulation, rising levels of estrogen exert positive feedback on the hypothalamus and anterior pituitary gland, leading to an increase in the secretion of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). FSH stimulates the growth and maturation of ovarian follicles, while LH triggers ovulation. 3. Describe the hormonal events at and after ovulation, be sure to include any positive or negative feedback discussed:  Hormonal events at and after ovulation : At ovulation, the surge in LH triggers the release of the mature egg from the ovarian follicle. After ovulation, the remaining follicle transforms into the corpus luteum, which secretes progesterone. Progesterone, along with estrogen, prepares the endometrium for potential implantation of a fertilized egg. If fertilization does not occur, the corpus luteum degenerates, leading to a decrease in progesterone levels and subsequent shedding of the uterine lining during menstruation.

BIOL 101: Guided Reading Questions (GRQs) Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment 4. Make a table of all the hormones that are part of the menstrual cycle, what cells secrete each of these hormones, and what cells are the target of each hormone. Hormone Secreted by Target cells GnRH Hypothalamus Anterior pituitary FSH Anterior pituitary Ovaries (granulosa cells) LH Anterior pituitary Ovaries (theca and granulosa cells) Estrogen Ovaries (follicles) Uterus, hypothalamus, anterior pituitary Progesterone Corpus luteum Uterus 5. Using Fig 27.6, Using the terms below, describe what happens to each through the 28-day cycle ( note: this cycle is not always 28 days and often varies in different individuals ) A. The uterus lining : During the follicular phase, the uterine lining thickens in response to rising estrogen levels. If fertilization does not occur, the uterine lining is shed during menstruation in the later part of the cycle. B. The ovaries : The ovaries undergo follicular development in the first half of the cycle, leading to the maturation of an egg. After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. C. The levels of FSH : FSH levels rise during the follicular phase to stimulate the growth and maturation of ovarian follicles. FSH levels decrease after ovulation due to negative feedback from rising estrogen levels. D. The levels of LH : LH levels surge just before ovulation, triggering the release of the mature egg from the follicle. LH levels decrease after ovulation but remain elevated to support the corpus luteum. E. The levels of estrogen : Estrogen levels rise during the follicular phase, peaking just before ovulation. After ovulation, estrogen levels decline temporarily but rise again during the luteal phase. F. The levels of progesterone : Progesterone levels increase during the luteal phase, primarily due to secretion by the corpus luteum. If fertilization occurs, progesterone levels remain elevated to support pregnancy. If fertilization does not occur, progesterone levels decrease, leading to the shedding of the uterine lining during menstruation. Module 27.7:Sexual activity can transmit disease 1. What the variables in the study described in Figure 27.7?

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BIOL 101: Guided Reading Questions (GRQs) Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment  Independent variables : Factors related to sexual behavior and practices, such as the number of sexual partners, frequency of sexual activity, use of protection (e.g., condoms), type of sexual activity (e.g., vaginal, anal), and history of sexually transmitted infections (STIs).  Dependent variables : Health outcomes related to disease transmission, such as the presence or absence of STIs (e.g., HIV, chlamydia, gonorrhea), rates of infection, changes in health status, and impact on overall well-being. 2. What is the conclusion of study? Module 27.8: Contraception can prevent unwanted pregnancy 1. Examine Figure 27.8 and order these from most effective to least effective at preventing pregnancy: pill—withdrawal – vasectomy – IUD – condom Ordering these contraceptive methods from most effective to least effective at preventing pregnancy:  IUD (Intrauterine Device) : Among the most effective contraceptive methods, with a very low failure rate.  Vasectomy : A permanent form of contraception for males, highly effective but irreversible.  Pill (Oral Contraceptive) : Highly effective when used correctly, but may have a slightly higher failure rate compared to long-acting reversible contraceptives (LARCs) like the IUD.  Condom : Effective at preventing pregnancy when used consistently and correctly, but may have a higher failure rate compared to other methods due to inconsistent use or breakage.  Withdrawal (Pulling out) : Least effective method among those listed, with a relatively high failure rate due to pre-ejaculate (pre-cum) containing sperm and difficulties with timing and consistency. 2. Which of these can prevent STIs? Condoms are the only method listed that can help prevent the transmission of sexually transmitted infections (STIs), including HIV, gonorrhea, chlamydia, and herpes. Proper and consistent use of condoms during sexual activity can significantly reduce the risk of STI transmission. However, it's important to note that condoms do not provide complete protection against all STIs, such as those transmitted through skin-to-skin contact (e.g., genital warts, herpes). More about IUDs: https://www.plannedparenthood.org/learn/birth-control/iud Module 27.9: Fertilization results in a zygote and triggers embryonic development

BIOL 101: Guided Reading Questions (GRQs) Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment 1. How does each structure of the sperm listed below (Fig 27.9B) support the functions of sperm.  Flagellum : The flagellum, or tail, propels the sperm forward through the female reproductive tract, allowing it to reach the egg for fertilization.  Mitochondria : Mitochondria provide energy to the sperm cell through the process of aerobic respiration. This energy is required for the flagellum to beat and propel the sperm, enabling its movement towards the egg.  Nucleus : The nucleus contains the genetic material (DNA) of the sperm, which carries the paternal genetic information needed for fertilization and embryo development.  Shape of Head : The head of the sperm is streamlined and tapered, which facilitates its penetration through the barriers of the female reproductive tract and allows it to reach the egg. The compact shape also aids in minimizing resistance during movement.  Acrosome : The acrosome is a specialized structure located at the tip of the sperm head. It contains enzymes that are released upon contact with the egg's zona pellucida (outer layer), allowing the sperm to penetrate and fertilize the egg by breaking down this protective barrier. 2. How is it ensured that only one sperm penetrates and fertilizes an egg?  Only one sperm is allowed to penetrate and fertilize an egg through a mechanism called the "fast block" and "slow block" to polyspermy.  Fast Block to Polyspermy : Upon fertilization, the egg undergoes a rapid change in its membrane potential, which depolarizes the egg membrane. This depolarization makes it temporarily resistant to the entry of additional sperm, preventing polyspermy.  Slow Block to Polyspermy : After the fast block, cortical granules within the egg are released into the perivitelline space (space between the egg membrane and zona pellucida). These cortical granules release enzymes that modify the zona pellucida, making it impermeable to other sperm and further preventing polyspermy.

Lesson 17_GRQs_Reproduction Part 2

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