IB Biology D3.1 Reproduction - Animal Physiology PDF

# IB Biology - D3.1 Reproduction - Animal Physiology ## Guiding Questions * How does asexual or sexual reproduction exemplify themes of change or continuity? * What changes within organisms are required for reproduction? ## Objectives * Contrast asexual and sexual reproduction * Outline the role...

# IB Biology - D3.1 Reproduction - Animal Physiology ## Guiding Questions * How does asexual or sexual reproduction exemplify themes of change or continuity? * What changes within organisms are required for reproduction? ## Objectives * Contrast asexual and sexual reproduction * Outline the roles of meiosis in sexual reproduction * Describe the structures and functions of the human male and female reproductive systems * Explain the hormonal control of the human menstrual cycle * Outline fertilization in humans * Describe IVF ## Sexual v Asexual Reproduction | Sexual Reproduction | Asexual Reproduction | |---|---| | Two parents | One parent | | Genetically diverse offspring | Genetically identical offspring | | Meiosis | Mitosis | | New combinations of traits | No propagation of genetic variation | ## Mitotic vs Meiotic Division **Mitotic division**: An image shows how one cell divides into two by replicating its DNA and then dividing the nucleus and the cytoplasm. The two daughter cells are genetically identical to the parent cell. **Meiotic divisions**: An image demonstrates meiosis. - DNA copies and then, after one round of division (Meiosis I) divides into two cells. - Then the replicated DNA in each cell is divided again (Meiosis II) resulting in four cells that are genetically different from the parent cell, each having single sets of chromosomes. ## Differences between male and female sexes in sexual reproduction Male gamete travels to the female gamete, so it is smaller, with less food reserves than the egg. From this follow differences in the numbers of gametes and the reproductive strategies of males and females. ## Meiosis & Gametes **Isogamy**: Two equal-sized gametes, may or may not be mobile. **Anisogamy**: Small gamete (male), large gamete (female). May or may not be mobile. **Oogamy**: Small mobile gamete (male), large immobile gamete (female). ## Human Reproductive Anatomy ### Male Reproductive Anatomy * **Seminal vesicle**: fructose * **Prostate gland**: alkali * **Sperm duct**: transport during ejaculation * **Urethra**: transport of semen and urine out of body * **Penis**: penetrates vagina * **Epididymis**: storage * **Scrotum**: lower temperature * ​**Testis**: sperm and testosterone ### Female Reproductive Anatomy * **Oviduct**: transfer to uterus * **Ovary**: produces eggs, oestradiol, and progesterone * **Uterus**:​ endometrium nourishes the growing embryo/fetus * **Cervix**: protects fetus during pregnancy * **Vagina**: birth canal * **Vulva**: protection ## Hormonal control of the menstrual cycle A diagram demonstrates the hormones involved in the menstrual cycle. * **Follicular Phase**: * **Endometrial Wall**: builds up * **Ovarian Hormones**: * Follicle Stimulating Hormone (FSH) increases * Estrogen increases, stimulating follicle development, and the thickening of the uterine lining in preparation for the potential implantation of a fertilized egg. * Luteinizing Hormone (LH) remains low. * **Ovulatory Phase**: * **Endometrial Wall**: Continues to thicken * **Ovarian Hormones**: * FSH decreases * Estrogen increases, stimulating the release of LH. * LH rapidly rises, triggering the release of the egg from the ovary. * **Luteal Phase**: * **Endometrial Wall**: Begins to break down * **Ovarian Hormones**: * FSH and LH decrease * Estrogen decreases * Progesterone increases, maintaining the uterine lining in the hopes that an egg was fertilized. The cycle repeats itself if an egg is not fertilized. ## Hormones in The Menstrual Cycle * Day 1-4 (Follicular phase): -Menstruation. Endometrium shed. -FSH increases, stimulating follicle development. * Day 5-14 (Ovulatory phase): -FSH and follicle stimulate oestrogen release -Oestrogen stimulates endometrium development -Oestrogen stimulates LH -Peak in LH causes ovulation (Day 14) * Day 14-28 (Luteal Phase): -Fall in LH. Corpus luteum forms from now-empty follicle -Corpus luteum releases progesterone -Progesterone maintains the endometrium and inhibits FSH and LH If no fertilisation and implantation occurs, progesterone and oestrogen drop, triggering menstruation and FSH release. ## Introduction to In Vitro Fertilisation (IVF) 1. After determining suitability for IVF, FSH and LH are given to stimulate multiple egg releases. 2. These eggs are collected. 3. Eggs are fertilised with father's sperm, in a dish, and incubated. This is 'IVF'. 4. After incubation, viable (fertilised) blastocysts are selected and developed into embryos. 5. Guidelines state that up to 3 embryos can be selected for implantation. Hopefully one or more will 'take'. There is a risk of multiple pregnancy. 6. After bedrest and a month or so, a pregnancy test is administered. If positive, pregnancy continues as normal. If not, a woman may wait a few months and attempt another cycle. ## Fertilization in Humans An image demonstrates the process of fertilization in humans. * **Egg**: The egg cell has its own protective layers: * **Vitelline layer**: with protein receptors that bind to sperm. * **Jelly coat**: a layer of glycoproteins that surround the egg plasma membrane. * **Cortical granule**: an organelle that contains enzymes that will block polyspermy (fertilization by more than one sperm). * **Sperm**: The sperm has the following components: * **Mitochondrial material**: an organelle that provides energy for the sperm. * **Nucleus**: contains the genetic material of the sperm. * **Acrosomal granule**: an organelle that contains enzymes that will help the sperm penetrate the egg’s protective layers. When a sperm successfully penetrates the egg, cortical granules are released, blocking further entry of sperm. The nuclei of the sperm and egg fuse, and the egg begins to divide, marking the beginning of development. ## IVF A diagram demonstrates how in vitro fertilization (IVF) works, including the steps of stimulating follicle growth, extracting oocytes, collecting sperm, in vitro fertilization, and implantation. * **Hormones**: * Down-regulation of FSH * High doses of FSH * hCG * Progesterone ## Explain the role of hormones in the regulation of the menstrual cycle * FSH and LH are produced by the pituitary gland; * estrogen and progestin are produced by the ovary; * FSH stimulates the ovary to promote development of a follicle; * The developing follicles secrete estrogen, which inhibits FSH (negative feedback); * Estrogen stimulates growth of endometrium; * Estrogen stimulates LH secretion (positive feedback); * LH stimulates follicle growth and triggers ovulation; * (the secondary oocyte leaves the ovary and) follicle becomes corpus luteum; * The corpus luteum secretes estrogen and progesterone; * Estrogen and progesterone maintain the endometrium; * Estrogen and progesterone inhibit LH and FSH (negative feedback); * After (two weeks) the corpus luteum degenerates progesterone and estrogen levels fall; * This triggers menstrual bleeding, the loss of endometrium; * The pituitary gland secreted FSH and LH, as they are no longer inhibited (and the menstrual cycle continues); **May credit marks that are clearly drawn and correctly labelled on diagrams or flow charts**