CHAPTER 42 Animal Reproduction

1. CHAPTER 42Animal Reproduction

2. Chapter 42: Animal Reproduction Asexual Reproduction Sexual Reproduction The Human Reproductive System Human Sexual Behavior

3. Asexual Reproduction • Some animals can reproduce asexually, producing offspring genetically identical to their parent and to one another. • A disadvantage of asexual reproduction is that no genetic diversity is produced. 3

4. Asexual Reproduction • Means of asexual reproduction include: • budding • regeneration • parthenogenesis Review Figure 42.2 4

5. figure 42-02.jpg Figure 42.2 Figure 42.2

6. Sexual Reproduction • Sexual reproduction consists of: gametogenesis, mating, and fertilization. • Gametogenesis and fertilization are similar in all animals, but mating includes a great variety of anatomical, physiological, and behavioral adaptations. 6

7. Sexual Reproduction • In sexually reproducing species, genetic diversity is created by recombination of genes during gametogenesis and independent assortment of chromosomes. • Mating and fertilization contribute to genetic diversity. 7

8. Sexual Reproduction • Gametogenesis occurs in testes and ovaries. • In spermatogenesis and oogenesis, the primary germ cells proliferate mitotically, undergo meiosis, and mature into gametes. Review Figure 42.4 8

9. Sexual Reproduction • Spermatogonia continue to proliferate by mitosis throughout the male’s lifespan. • Each primary spermatocyte can produce four haploid sperm through the two divisions of meiosis. Review Figure 42.4a 11

10. figure 42-04a.jpg Figure 42.4 – Part 1 Figure 42.4 – Part 1

11. Sexual Reproduction • Primary oocytes immediately enter prophase of the first meiotic division, and in many species, their development is arrested at this point. • Each oogonium produces only one egg through meiosis. Review Figure 42.4b 12

12. figure 42-04b.jpg Figure 42.4 – Part 2 Figure 42.4 – Part 2

13. Sexual Reproduction • Hermaphroditic species have both male and female reproductive systems in the same individual, sequentially or simultaneously. 13

14. Sexual Reproduction • Fertilization can occur externally, which is common in aquatic species, or internally, which is common in terrestrial species. • Internal fertilization usually involves copulation. 14

15. Sexual Reproduction • Internal fertilization is necessary for nonaquatic species. • The shelled egg is an important adaptation to the desiccating terrestrial environment, but must be fertilized before shell formation. • All mammals except monotremes retain the embryo internally and do not produce shelled eggs. 15

16. Sexual Reproduction • Animals can be classified as oviparous or viviparous depending on whether the early stages of development occur outside or inside the mother’s body. 16

17. The Human Reproductive System • Males produce and deliver semen into the female reproductive tract. • Semen consists of sperm suspended in a fluid that nourishes them and facilitates fertilization. 17

18. The Human Reproductive System • Sperm are produced in seminiferous tubules, mature in the epididymis, and are delivered to the urethra through the vasa deferentia. • Other components of semen are produced in the seminal vesicles, prostate gland, and bulbourethral glands. • All components of semen join in the urethra and are ejaculated through the penis by muscle contractions. Review Figures 42.8, 42.9 18

19. figure 42-08.jpg Figure 42.8 Figure 42.8

20. figure 42-09a.jpg Figure 42.9 – Part 1 Figure 42.9 – Part 1

21. figure 42-09b.jpg Figure 42.9 – Part 2 Figure 42.9 – Part 2

22. The Human Reproductive System • Spermatogenesis depends on testosterone secreted by Leydig cells in the testes, controlled by luteinizing hormone from the pituitary. • Spermatogenesis is also controlled by follicle-stimulating hormone from the pituitary. • Hypothalamic gonadotropin-releasing hormone controls secretion of LH and FSH. • Production of these hormones by the hypothalamus and pituitary is controlled by negative feedback from testosterone and inhibin. Review Figure 42.10 22

23. figure 42-10.jpg Figure 42.10 Figure 42.10

24. The Human Reproductive System • Eggs mature in the female’s ovaries and are released into the oviducts, which deliver the eggs to the uterus. • Sperm deposited in the vagina during copulation move through the cervix into the uterus, some continuing up through the oviducts. Review Figure 42.11 24

25. figure 42-11.jpg Figure 42.11 Figure 42.11

26. The Human Reproductive System • Fertilization occurs in the upper regions of the oviducts. • The zygote becomes a blastocyst through cell divisions as it passes down the oviduct. • Upon arrival in the uterus, it implants in the endometrium, where a placenta forms and the embryo develops. 26

27. The Human Reproductive System • The maturation and release of ova constitute an ovarian cycle under the control of the anterior pituitary hormones FSH and LH. • In humans, this cycle takes about 28 days. Review Figures 42.12, 42.13 27

28. figure 42-12.jpg Figure 42.12 Figure 42.12

29. figure 42-13a.jpg Figure 42.13 – Part 1 Figure 42.13 – Part 1

30. figure 42-13b.jpg Figure 42.13 – Part 2 Figure 42.13 – Part 2

31. The Human Reproductive System • The uterus also undergoes a cycle that prepares it for receipt of a blastocyst. • If none is implanted, the uterus lining deteriorates and sloughs off, which is menstruation. Review Figure 42.13 31

32. The Human Reproductive System • The ovarian and the uterine cycles are under the control of hypothalamic and pituitary hormones, which in turn are under the feedback control of estrogen and progesterone. Review Figure 42.14 32

33. figure 42-14.jpg Figure 42.14 Figure 42.14

34. Human Sexual Behavior • Human sexual responses consist of: excitement, plateau, orgasm, and resolution. • Males have a refractory period during which renewed excitement is not possible. 34

35. Human Sexual Behavior • Methods to prevent pregnancy include abstention from copulation or use of technologies that decrease the probability of fertilization. Review Table 42.1 35

36. table 42-01.jpg Table 42.1 Table 42.1

37. Human Sexual Behavior • Barrier methods of contraception block the passage of sperm in the female reproductive tract or weaken and kill them. 37

38. Human Sexual Behavior • Methods to prevent ovulation interfere with the ovarian cycle so that mature, fertile ova are not produced and released. 38

39. Human Sexual Behavior • Males and females can be sterilized by surgical blockage of the vasa deferentia or oviducts. Review Figure 42.15 39

40. figure 42-15.jpg Figure 42.15 Figure 42.15

41. Human Sexual Behavior • Methods to prevent implantation of a blastocyst include intrauterine devices, excess doses of steroids, and a progesterone receptor blocker. • After implantation, pregnancy termination is called an abortion. 41

42. Human Sexual Behavior • Assisted reproductive technologies have been developed to increase fertility. • ARTs include in vitro fertilization and gamete intrafallopian transfer. 42

43. Human Sexual Behavior • Sexually transmitted diseases result from the transmission of disease-causing organisms through sexual behavior. • Many STD’s are curable if treated early, but can have serious long-term consequences if untreated. Review Table 42.2 43

44. table 42-02a.jpg Table 42.2 – Part 1 Table 42.2 – Part 1

45. table 42-02b.jpg Table 42.2 – Part 2 Table 42.2 – Part 2