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Chapter 20

Chapter 20. Is There Something in the Water? Reproductive and Developmental Biology. Chapter 20 Section 1. Principles of Animal Reproduction. 20.1 Principles of Animal Reproduction. Two main types of reproduction Asexual reproduction Sexual reproduction Asexual Reproduction

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Chapter 20

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  1. Chapter 20 Is There Something in the Water?Reproductive and Developmental Biology

  2. Chapter 20 Section 1 Principles of Animal Reproduction

  3. 20.1 Principles of Animal Reproduction Two main types of reproduction • Asexual reproduction • Sexual reproduction Asexual Reproduction • one parent produces offspring that are genetically identical to the parent

  4. 20.1 Principles of Animal Reproduction Two main types of asexual reproduction • Binary fission – cells break away from parent to form offspring (e.g., sponges) • Budding – daughter cell remains attached to parent and breaks away when mature (e.g., hydra)

  5. 20.1 Principles of Animal Reproduction – Sexual Reproduction • Sexual reproduction combines genomes of two individuals to create variable offspring • Females = individuals that produce large gametes (sex cells) • Males = individuals that produce small gametes • Gonads = Organs that produce gametes • Male gonad = testes • Female gonad = ovaries

  6. 20.1 Principles of Animal Reproduction Methods of fertilization • Internal fertilization – sperm deposited by copulation in or near female reproductive tract. • Mammals, birds, reptiles, and sharks use internal fertilization. • External fertilization – eggs laid, male deposits sperm over eggs (usually in water). Most fish and amphibians use external fertilization. • Very susceptible to contaminants

  7. 20.1 Principles of Animal Reproduction Environmental Contaminants and Sexual Reproduction • Developing frogs are extremely sensitive to environmental chemicals • Eggs develop in water • Embryos absorb toxins easily • Frogs are declining globally Figure 20.2

  8. 20.1 Principles of Animal Reproduction - Endocrine Disruptors • Man-made chemicals alter endocrine regulation • interferes with normal gonad development. • Male amphibians have been feminized. • These chemicals affect animals living in water. • Are humans affected by drinking contaminated water?

  9. End Chapter 20 Section 1 Principles of Animal Reproduction

  10. Chapter 20 Section 2 Part A Human Reproduction: Males

  11. 20.2 Human Reproduction Male Reproductive Anatomy • Penis • Contains spongy erectile tissue • Fills with blood to cause erection • Testes • Inside scrotum • Produce sperm and testosterone Figure 20.4

  12. 20.2 Human Reproduction Male Reproductive Anatomy • Accessory Glands • Prostate & seminal vesicles • Secrete fructose, mucous • Testes • Inside scrotum • produce sperm and testosterone • Epididymis • Stores sperm • Vas deferens & urethra Figure 20.4

  13. 20.2 Human Reproduction Endocrine Disruptors & Humans • Men • Most common cause of male infertility is the inability to produce healthy sperm. • Sperm counts are declining globally

  14. 20.2 Human Reproduction Gametogenesis = production of gametes (germ cells) • Involves meiosis • Reduces number of chromosomes by ½ • Human body cells contain 46 chromosomes, gamete contain 23 • (see chapter 5 for review) • Male and female gametes undergo further development to become functional

  15. 20.2 Human Reproduction Spermatogenesis • Seminiferous tubules = functional unit of testis • Contain developing sperm cells • Sertoli cells – nurse cells for sperm • Leydig cells outside seminiferous tubules • Make and release testosterone Figure 20.6

  16. 20.2 Human Reproduction Cell types in Spermatogenesis • Spermatogonia • Stem cells • Divide by mitosis • Primary spermatocytes • Enter Meiosis I • Secondary spermatocytes • Enter meiosis II • Spermatids • Undergospermiation • Cytodifferentiation • Spermatozoa Figure 20.6

  17. 20.2 Human Reproduction Spermatozoa Structure • Head • Condensed nucleus • Acrosome • Contains enzymes for fertiliztion • Midpiece • Lots of mitochondria • Tail • Flagellum for swimming Figure 20.6

  18. 20.2 Human Reproduction - Male Infertility Human infertility and endocrine disruptors • 90% of male infertility is related to problems with sperm formation or production • Low sperm counts • Improperly shaped sperm • Low motility • Chemical exposure (e.g., pesticides) can decrease sperm viability • Male infertility also increases with alcohol and drug use, including cigarettes • Sperm counts declining globally since WWII

  19. 20.2 Human Reproduction PLAY Animation—The Male Reproductive System

  20. End Chapter 20 Section 2 Part A Human Reproduction: Males

  21. Chapter 20 Section 2 Part B Human Reproduction: Females

  22. 20.2 Human Reproduction Female Reproductive Anatomy • External genitalia • Labia majora & labia minora • clitoris • Reproductive tract • Vagina • Uterus • Paired oviducts • Fertilization • Separate urethral opening Figure 20.5

  23. 20.2 Human Reproduction Female Reproductive Anatomy • Ovaries • Endocrine • Estrogen • Progesterone • Produces gametes • Follicle contains: • Egg • Endocrine cells Figure 20.5

  24. 20.2 Human Reproduction Endocrine Disruptors & Humans • Women • DES is a drug that acts as an endocrine disruptor. • Given to women to prevent premature delivery • Daughters of women who took DES have a higher rate of infertility.

  25. 20.2 Human Reproduction Oogenesis • Two parts • Oocyte development • Follicular development Figure 20.7

  26. 20.2 Human Reproduction Oocyte Development • All oogonia (stem cells) become primaryoocytes during her (the mother’s) embryonic development • Each month during menstrual cycle • Primary oocytesenter meiosis I -> secondary oocytes • Secondary oocytescomplete meiosis II at fertilization • Polar bodies will deteriorate Figure 20.7

  27. 20.2 Human Reproduction Follicular Development • Follicles include oocytesand surrounding endocrine cells • Primary follicle stores primary oocytes until use • FSH causes development to secondary follicle and then Graffian follicle (both with secondary oocyte) • Secrete estrogen • LH causes ovulation • Follicle become corpus luteum • Secretes estrogen & progesterone Figure 20.7

  28. 20.2 Human Reproduction The Menstrual Cycle • Changes in the uterine endometrium • Prepares endometrium for pregnancy • Regulated by: • Pituitary FSH & LH • Ovarian estrogen & progesterone Figure 20.8

  29. 20.2 Human Reproduction The Menstrual Cycle • Days 1-4 • Menstruation • Only FSH elevated • causes new follicle to grow • Days 5-14 • FSH causes follicle to grow & release estrogen • Estrogen causes endometrium to grow Figure 20.8

  30. 20.2 Human Reproduction The Menstrual Cycle • Day 14 • Surge of LH causes ovulation & corpus luteum formation Figure 20.8

  31. 20.2 Human Reproduction The Menstrual Cycle • Day 14-28 • FSH & LH cause ovary to secrete estrogen & progesterone • Prepares for pregnancy • Corpus luteum dies at end of cycle • Results in collapse of endometrium and start of menstruation Figure 20.8

  32. 20.2 Human Reproduction Regulating The Menstrual Cycle Regulation involves both positive & negative feedback loops • High estrogen causes positive feedback on LH • Leads to LH surge • High progesterone causes negative feedback on LH & FSH Figure 20.9

  33. 20.2 Human Reproduction Pregnancy • If the egg is fertilized, embryo secretes human chorionic gonadotropin (hCG) • hCG mimics LH and keeps corpus luteum alive • Progesterone maintains endometrium during pregnancy Birth Control Pills • Mimic pregnancy by providing estrogen and progesterone • prevent ovulation by blocking LH surge Figure 20.9

  34. 20.2 Human Reproduction Female Infertility • One cause of female infertility is endometriosis • a condition where the endometrial cells can attach to the ovaries & oviducts • also grow and shed during menstrual cycle • Can cause damage and scarring to ovarian tissue • Can disrupt ovulation • Painful • May be related to exposure to environmental chemicals like DEHP

  35. 20.2 Human Reproduction PLAY Animation—The Female Reproductive System

  36. End Chapter 20 Section 2 Part B Human Reproduction: Females

  37. Chapter 20 Section 3 Human Development Chapter 20 Section 4 Is the Water Safe to Drink?

  38. 20.3 Human Development Fertilization • Sperm penetrate follicle cells • Sperm head binds to zona pellucida • Acrosome enzymes released • Egg & sperm membranes fuse • Sperm nucleus enters egg cell Figure 20.11

  39. 20.3 Human Development Endocrine Disruptors and Fertilization • Industrial solvents can mimic hormones and interfere with sperm development and fertilization. • Misshapen sperm cannot swim effectively and are unable to fertilize egg. • Males exposed to solvents, working as mechanics or dry cleaners, have a larger number of abnormal sperm. • While effect on adults lowers fertility, effects on developing fetus is more severe

  40. 20.3 Human Development Human Embryonic Development • Human zygote undergoes a series of cleavages to produce an embryo • Embryo is stage from zygote until body structures appear • Blastocyst = hollow ball of cells • Gastrula = tissue layers start to appear Figure 20.12

  41. 20.3 Human Development - Human Embryonic Development Gastrula has 3 tissue layers • Endoderm – forms digestive & respiratory • Mesoderm – forms muscles, skeleton, excretory, circulatory, & gonads • Ectoderm – forms skin, nervous & sensory • Growth of a particular tissue or organ relies on chemical stimulus • Very sensitive to chemical disruption

  42. 20.3 Human DevelopmentDevelopment of Human Reproductive Organs • Male & female organs develop from same embryonic precursors • Hormonal signals cause development of male and female reproductive organs Table 20.3

  43. 20.3 Human DevelopmentEndocrine Disruptors & Reproductive Organs • Chemicals can pass from mother’s blood to fetus • Common herbicides & fungicides can cause cryptorchidism • Undescended testes • 2 to 4 % of human males are now born with undescended testes Table 20.3

  44. 20.3 Human DevelopmentPregnancy or Gestation • A placenta must develop to sustain pregnancy • Embryo blastocyst implants in the wall of the uterus • Maternal and fetal blood supplies are closely intertwined, allowing exchange of nutrients and wastes • 9 week old fetus has all its limbs and organs in place • Environmental chemicals can seriously effect embryo & fetus

  45. 20.3 Human Development Childbirth • Decreasing estrogen in late pregnancy induces oxytocin receptors to form in uterine muscle • Hormone oxytocin uses a positive feedback loop to induce labor. Figure 20.15

  46. 20.4 Is the Water Safe to Drink? Human correlations with endocrine disruptors • abnormal sperm • lower sperm counts • decreased fertility • cryptorchidism • endometriosis • uterine abnormalities EPA requires monitoring of municipal water supplies. • But it’s unclear what chemicals to monitor and what is a safe level of chemicals

  47. Chapter 20 Section 3 Human Development Chapter 20 Section 4 Is the Water Safe to Drink?

  48. End Chapter 20 Section 2 Human Reproduction

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