1. Animal reproduction can occur through asexual or sexual reproduction. Asexual reproduction produces offspring without fusion of gametes but maintains parental traits, while sexual reproduction allows for genetic variability through gamete fusion. 2. Sexual reproduction in animals involves complex reproductive systems with gonads that produce gametes and accessory structures for gamete transport and nourishment. Fertilization can be internal or external. 3. After fertilization, the embryo undergoes cleavage and then gastrulation to form the germ layers and begin organ development. Hormones coordinate the reproductive cycles.

1. Animal Reproduction AP Chapter 46

2. Asexual vs Sexual?

3. Asexual Reproduction Types: fission, budding, fragmentation and regeneration, parthenogenesis (Parthenogenesis is the development of a new individual from an unfertilized egg) Produces many more offspring Maintains “good” traits

4. Sexual Reproduction Fusion of gametes Allows for more genetic variability and ability to withstand changing environments

5. Fig. 46-1

6. Strange sexual things… Individuals of some species undergo sex reversals Some species exhibit male to female reversal (for example, certain oysters), while others exhibit female to male reversal (for example, a coral reef fish)

7. What about hermaphrodites self-fertilizing? This is sexual reproduction since this involves the union of eggs and sperm and these are not identical due to meiosis and crossing-over.

8. Is fertilization successful? External – moist habitat, many gametes shed Internal – placement of sperm near the egg, copulatory organs, sperm receptacles, behavioral cooperation All fertilization requires critical timing, often mediated by environmental cues, pheromones, and/or courtship behavior

9. Fig. 46-5 Eggs

10. Helping the embryo survive Species with internal fertilization provide greater protection of the embryos and more parental care The embryos of some terrestrial animals develop in amniote eggs with protective layers Some other animals retain the embryo , which develops inside the female In many animals, parental care helps ensure survival of offspring

11. Fig. 46-6

12. Gamete Production and Delivery In most species individuals have gonads , organs that produce gametes Some simple systems do not have gonads, but gametes form from cells lining the coelom as in polychaete worms The most complex systems contain many sets of accessory tubes and glands that carry, nourish, and protect gametes and developing embryos

13. Most insects have separate sexes with complex reproductive systems In many insects, the female has a spermatheca in which sperm is stored during copulation

14. Fig. 46-7 Accessory gland Ejaculatory duct Testis Vas deferens Seminal vesicle Penis Ovary Oviduct Spermatheca Vagina Accessory gland (a) Male honeybee (drone) (b) Female honeybee (queen)

15. A cloaca is a common opening between the external environment and the digestive, excretory, and reproductive systems A cloaca is common in nonmammalian vertebrates; mammals usually have a separate opening to the digestive tract

16. Female Reproductive System The internal organs are a pair of gonads and a system of ducts and chambers that carry gametes and house the embryo and fetus

17. Fig. 46-10 Oviduct Ovary Uterus (Urinary bladder) (Pubic bone) Urethra (Rectum) Cervix Vagina Shaft Glans Prepuce Clitoris Labia minora Labia majora Vaginal opening Ovaries Uterus Follicles Oviduct Cervix Corpus luteum Uterine wall Endometrium Vagina

18. Ovaries The female gonads, the ovaries, lie in the abdominal cavity Each ovary contains many follicles, which consist of a partially developed egg, called an oocyte, surrounded by support cells During each menstrual cycle, a maturing follicle produces estradiol (estrogen). Following ovulation, the follicle forms a solid mass called the corpus luteum .

20. path of the egg The egg cell is expelled into the abdominal cavity and swept into the oviduct or Fallopian tubes, and then moves into the uterus. The lining of the uterus, the endometrium is highly vascularized. The neck of the uterus, the cervix , opens into the vagina , the elastic-walled birth canal.

21. Path of the Egg

22. Male Reproductive Anatomy Internal organs are the gonads, which produce sperm and hormones, and accessory glands

23. Fig. 46-11 Seminal vesicle (behind bladder) (Urinary bladder) Prostate gland Bulbourethral gland Erectile tissue of penis Urethra Scrotum Vas deferens Epididymis Testis Seminal vesicle (Urinary bladder) (Urinary duct) (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum (Pubic bone) Erectile tissue Urethra Glans Prepuce Penis

24. sperm production In the male, the sperm are produced in the coiled seminiferous tubules of the testes. Leydig cells produced testosterone and other androgens. Sperm production requires a lower temperature than the internal body temp of most mammals, so the scrotum suspends testes below the abdominal cavity.

25. Accessory Glands of the male Seminal vesicles - contribute about 60% of the total volume of semen Prostate gland Bulboureothral glands These add mucus, fructose for energy, prostaglandins, and other substances needed for the movement of the sperm. As for pH, the sperm is alkaline.

26. Sperm Each 2 – 5 mL of ejaculated semen contains 100 to 650 million sperm.

27. The head of the sperm contains a haploid nucleus and is tipped with an acrosome which contains enzymes to penetrate the egg. Mitochondria provide ATP for movement. Fig. 46-12d

28. The timing and pattern of meiosis in mammals differ for males and females Gametogenesis , the production of gametes by meiosis, differs in females and males Sperm are small and motile and are produced throughout the life of a sexually mature male Spermatogenesis is production of mature sperm Eggs contain stored nutrients and are much larger Oogenesis is development of mature oocytes (eggs) and can take many years. Meiosis I (Prophase I) is arrested before birth, completed once monthly at puberty until Metaphase II stage. Final completion at fertilization.

29. Fig. 46-12a Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Sertoli cell nucleus Primordial germ cell in embryo Mitotic divisions Spermatogonial stem cell Mitotic divisions Mitotic divisions Spermatogonium Primary spermatocyte Meiosis I Meiosis II Secondary spermatocyte Lumen of seminiferous tubule Plasma membrane Tail Neck Midpiece Head Mitochondria Nucleus Acrosome Spermatids (at two stages of differentiation) Early spermatid Differentiation (Sertoli cells provide nutrients) Sperm 2 n 2 n 2 n n n n n n n n n n n

30. Fig. 46-12f Ovary Primary oocyte within follicle Ruptured follicle Growing follicle Mature follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum

31. Fig. 46-12g Primordial germ cell Mitotic divisions Oogonium Mitotic divisions Primary oocyte (present at birth), arrested in prophase of meiosis I Completion of meiosis I and onset of meiosis II Secondary oocyte, arrested at metaphase of meiosis II First polar body Ovulation, sperm entry Completion of meiosis II Second polar body Fertilized egg 2 n 2 n n n n n In embryo In Embryo At fertilization At puberty

32. Differences overall in spermatogenesis and oogenesis Spermatogenesis is a continuous process after beginning at puberty. Oogenesis is interrupted. Spermatogenesis results in 4 sperm. Oogenesis results in ONE egg and polar bodies. Males produce sperm continuously but females are born with a certain number of primary oocytes. Also oogenesis stops in females at menopause.

33. Fig. 46-UN1 Gametogenesis Spermatogenesis Oogenesis Primary spermatocyte Primary oocyte Polar body Secondary spermatocytes Secondary oocyte Spermatids Sperm Polar body Fertilized egg n 2 n 2 n n n n n n n n n n n n n n

34. the role of Hormones in reproduction Human reproduction is coordinated by hormones from the hypothalamus, anterior pituitary, and gonads Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and directs the release of FSH and LH from the anterior pituitary FSH (Follicle Stimulating Hormone) and LH (Leutinizing Hormone) regulate processes in the gonads and the production of sex hormones

35. GnRH hypothalamus FSH, LH pituitary gland Estrogen, progesterone ovary Testosterone testes

36. The sex hormones are androgens, estrogens, and progesterone Sex hormones regulate: The development of primary sex characteristics during embryogenesis The development of secondary sex characteristics at puberty Sexual behavior and sex drive

37. Both males and females secrete FSH and LH In males: FSH promotes the activity of Sertoli cells, which nourish developing sperm and are located within the seminiferous tubules LH regulates Leydig cells, which secrete testosterone and other androgen hormones, which in turn promote spermatogenesis

38. Fig. 46-13 Hypothalamus GnRH FSH Anterior pituitary Sertoli cells Leydig cells Inhibin Spermatogenesis Testosterone Testis LH Negative feedback Negative feedback – – –

39. In females: FSH – stimulates follicle growth LH – stimulates the change of the ruptured follicle to the corpus luteum

40. The Reproductive Cycles of Females Involves the uterine cycle (menstrual cycle), the ovarian cycle, and the pituitary hormones (FSH and LH) These work together approximately every 28 days to prepare the uterus for a fertilized egg. The inner layer of the uterus, the endometrium, thickens to prepare for implantation of a fertilized egg. If fertilization does not occur, menstruation occurs in which this layer is shed.

41. Ovarian Cycle Follicular Phase The release of GnRH from the hypothalamus stimulates the anterior pituitary to secrete small amounts of FSH and LH . FHS stimulates follicular growth. The cells of the follicle secrete the hormone estradiol which further encourages more GnRH hormone and thus more FSH and LH (+ feedback). The increase in LH induces maturation of the follicle and ovulation about a day after the LH surge.

42. Ovarian Cycle Luteal Phase The ruptured follice becomes a corpus luteum which secretes estradiol and progesterone. The increase of these hormones exert a negative feedback on the hypothalamus and pituitary, inhibiting secretion of FSH and LH. Once the corpus luteum disintegrates, it can no longer produce estradiol and progesterone so the pituitary and hypothalamus once more begin to make FSH and LH.

43. Fig. 46-14a Control by hypothalamus Inhibited by combination of estradiol and progesterone Stimulated by high levels of estradiol Inhibited by low levels of estradiol Hypothalamus GnRH Anterior pituitary FSH LH Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Growing follicle Maturing follicle Corpus luteum Degenerating corpus luteum Follicular phase Ovulation Luteal phase (a) (b) (c) Days 0 5 10 14 15 20 25 28 | | | | | | | | – – +

44. Uterine Cycle – controlled by hormones from the ovary Proliferative Phase : the endometrium begins to thicken due to influence from estradiol Secretory Phase : after ovulation, estradiol and progesterone stimulate increased vascularization of the endometrium and the development of glands that secrete a nutrient fluid.

45. Menstrual Flow Phase : Rapid drop in ovarian hormones caused by the distintegration of the corpus luteum reduces blood supply to the endometrium and begins its disintegration, leading to menstruation.

46. Fig. 46-14b Ovarian hormones in blood Peak causes LH surge Estradiol level very low Estradiol Progesterone Ovulation Progesterone and estra- diol promote thickening of endometrium Uterine (menstrual) cycle Endometrium 0 5 10 14 20 25 28 | | | | | | | | Days 15 Menstrual flow phase Proliferative phase Secretory phase (d) (e)

47. A new cycle begins if no embryo implants in the endometrium Cells of the uterine lining can sometimes migrate to an abnormal, or ectopic, location Swelling of these cells in response to hormone stimulation results in a disorder called endometriosis

48. Menopause After about 500 cycles, human females undergo menopause , the cessation of ovulation and menstruation Menopause is very unusual among animals Menopause might have evolved to allow a mother to provide better care for her children and grandchildren

49. Estrous cycles are characteristic of most mammals: The endometrium is reabsorbed by the uterus Sexual receptivity is limited to a “heat” period The length and frequency of estrus cycles varies from species to species

50. Questions Most birth control methods are designed to keep the egg and sperm from uniting to form a zygote? Many birth control pills or patches used by human females contain a combination of estrogen and progesterone. How do they keep sperm from uniting with the egg?

51. Questions Efforts to make a male contraceptive pill have not been very successful. Given what you know about the similarities and differences in male and female gamete production, propose why this might be the case.

52. Fertilization generally occurs in the upper third of the oviduct, and development of the fetus occurs in the uterus. In some relatively rare cases, developing embryos have attached to the outside of the uterus and developed for the full 9 months. How could this happen? What modifications of normal birthing procedures (if any) would have to be made in such cases?

53. Which would prevent pregnancy? A vaccine against LH A vaccine against hCG? A vaccine against estrogen? A vaccine against prolactin?

54. If fertilization occurs…

55. Occurs in Fallopian Tubes (oviducts) (usually) When 1 sperm penetrates the zona pellucida (clear zone around egg), cortical granules are released that prevent any other sperm from penetrating the egg

56. The release of calcium ions stimulates the cortical reaction The sperm enters and binds to the egg surface. This induces a calcium wave that causes the cortical granules, white, to fuse with the plasma membrane, releasing their contents and causing the fertilization membrane to rise. The sperm is then pulled into the egg where it moves to the egg nucleus and fuses.

57. Is this cell signaling? You betcha! IP3 and calcium ion wave production after ligand binds receptor - shaockwave Flash animation

58. Cleavage : The first days and weeks after conception: mitotic cell divisions begin, converting the zygote to a multicellular organism Day 1 : first cleavage - 1 cell becomes 2 Day 2: second cleavage - 4-cell stage Day 3: 6-12 cell stage - can test at this stage for genetic diseases if done by IVF Day 4 : 16-32 cell stage - solid ball of cells - morula

59. Day 5 : Solid morula develops into hollow, fluid-filled blastula The embryo will develop from the inner cell mass, or embryonic disc ICM

60. Where stem cells are pluripotent

61. Day 6 -7: Blastocyst attaches to the endometrium and burrows in: implantation . - The blastocyst starts to secrete HCG - human chorionic gonatotropin - Stimulates estrogen and progesterone to prevent menstrual flow -Causes "morning sickness" in some women... -Pregnancy test measures the amount of this hormone

62. Fig. 46-15 Ovary Uterus Endometrium (a) From ovulation to implantation (b) Implantation of blastocyst Cleavage Fertilization Ovulation Cleavage continues The blastocyst implants Trophoblast Inner cell mass Cavity Blastocyst Endo- metrium 1 2 3 4 5

63. Days 7-10: Gastrulation: major cellular reorganization into 2 or 3 tissue (germ) layers: -Ectoderm : skin, nervous system -Endoderm : lining of gut and internal organs -Mesoderm : muscles, bones, heart Gastrula : Early embryo with 3 tissue layers . All cells have the same DNA; however, different cells now begin to "turn on" (or "express") different genes to become different organs.

64. Days 10 - 14: Pregnancy becomes established -Fluid filled amniotic cavity starts to form -Yolk sac starts to form (will make blood cells, germ cells) -Embryo starts to form from embryonic disc - Chorion (placenta) starts to form At the end of this stage, a woman will have just missed her period!

66. Days 15 - 21: Emergence of the vertebrate body plan Primitive streak starts to form - this is the site of gastrulation (formation of the 3 tissue layers - ecto, endo, and mesoderm) Neural groove (future spinal cord and brain) begins to form Somites (bands of tissue that will become muscles and bones) begin to form Pharangeal arches (future face, neck, mouth, nose) begin to form

68. Days 21 on... Week 3 - Week 8 (Embryo) - Development of all organ systems Day 22: Cardiac cells (early heart) begins to beat Day 24 embryo shown at right

69. The first 3 weeks are the most hazardous periods in your life. Roughly one third to one half of all fertilized zygotes never make it beyond this point . Sadly, many women will have at least one miscarriage in their childbearing years. Some of the critical errors that can cause a miscarriage are:

70. 1) Inheritance of a defective set of chromosomes . Errors in meiosis (called nondisjunction ) can produce an egg or sperm that has an abnormal number of chromosomes or broken chromosomes. This is almost always lethal. About half of the early miscarriages in humans are afflicted with this kind of random chromosomal defect.

71. 2) Errors in mitosis after fertilization . Since the blastula has so few cells, that means a significant fraction of the embryo is defective, preventing further development.

72. 3) Implantation errors. Human embryos have to nestle down in a good home, in the uterus. If the mother's hormones are not just right, that can prevent implantation, and the otherwise healthy zygote may be sloughed away. In addition, 0.5 - 1% of all pregnancies are ectopic : the zygote tries to implant in the wrong place, most often in the fallopian tubes. This is always fatal for the embryo, and has the potential to be fatal for the mother."

73. Week 4: How you looked at 1 month past conception....

74. Week 7 / Day 48 : First brain waves can be detected Week 4-8 is whan all the major organ systems of the body are formed and when most teratogens have their greatest effect Week 8

75. Week 8 - 36: (Fetus) : After 12 weeks or so, the baby's development is largely "finished" - except brain and lung development The fetus just spends much of the 2nd and 3rd trimesters just growing (and doing various flip-turns and kicks inside the amniotic fluid)

76. And then, before you know it...

78. The embryo secretes human chorionic gonadotropin (hCG) which maintains the corpus luteum’s secretion of progesterone and estrogen for the first few months. After implantation, the outer layer of the blastocyst, the trophoblast , forms the placenta which exchanges gases and nutrients with the mother.

79. Blood from the embryo travels to the placenta through arteries of the umbilical cord and returns via the umbilical vein The placenta takes over the continued secretion of progesterone during the second trimester until birth.

80. Fig. 46-16 Placenta Uterus Umbilical cord Chorionic villus, containing fetal capillaries Maternal blood pools Maternal arteries Maternal veins Maternal portion of placenta Fetal arteriole Fetal venule Umbilical cord Fetal portion of placenta (chorion) Umbilical arteries Umbilical vein

81. Fig. 46-17 (a) 5 weeks (b) 14 weeks (c) 20 weeks

82. Fig. 46-18 Estradiol Oxytocin from ovaries Induces oxytocin receptors on uterus from fetus and mother’s posterior pituitary Stimulates uterus to contract Stimulates placenta to make Prostaglandins Stimulate more contractions of uterus Positive feedback + +