1. BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 27 Reproduction and Embryonic Development

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings There are no male desert-grassland whiptail lizards The species reproduces without copulation or fertilization Mating Without Males

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings This photo shows a ritual behavior that primes a female to lay eggs –The female on top behaves much like a male in other species of whiptail lizards Mating behavior seems to be an evolutionary leftover

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Although the reproduction method of desert- grassland whiptails is unusual, their embryonic development is similar to all other animal species Reptiles, birds, and mammals have four embryonic membranes Chorion Amnion Allantois Yolk sac Yolk Embryo Shell

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings All animal species have three stages of embryonic development –Mitotic cell division –Cellular differentiation –Formation of the body and its structures

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Asexual reproduction –Budding –Fission –Fragmentation, accompanied by regeneration –Development of an unfertilized egg 27.1 Sexual and asexual reproduction are both common among animals ASEXUAL AND SEXUAL REPRODUCTION Figure 27.1A

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sexual reproduction –The fission of two haploid gametes from two parents to form a diploid zygote Figure 27.1D

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Rotifers can reproduce both asexually and sexually Hermaphroditism –A single individual has both male and female reproductive systems Figure 27.1B, C “Head” Intestine Ovary Eggs

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Advantages of asexual reproduction –A single individual reproduces –Many offspring are produced rapidly Disadvantage of asexual reproduction –Little or no genetic variation

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Advantages of sexual reproduction –Increases genetic variation –Enhances reproductive success in changing environments Disadvantage of sexual reproduction –Locating a mate

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ovaries –Contain follicles that nurture eggs –Produce sex hormones Oviducts –Convey eggs to the uterus 27.2 Reproductive anatomy of the human female HUMAN REPRODUCTION OvariesOviduct FolliclesCorpus luteum UterusWall of uterus Endometrium (lining of uterus) Vagina Cervix (“neck” of uterus) Figure 27.2A

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Development of fertilized egg –Opens into the vagina Vagina –Receives penis during intercourse –Forms the birth canal Uterus OvariesOviduct FolliclesCorpus luteum UterusWall of uterus Endometrium (lining of uterus) Vagina Cervix (“neck” of uterus) Figure 27.2A

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ovulation Figure 27.2B Egg cell –An egg cell is released from a follicle at the surface of an ovary –The orange mass below the ejected oocyte is part of the ovary

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.2C Rectum (digestive system) Cervix Vagina Bartholin’s gland Vaginal opening Oviduct Ovary Uterus Bladder (excretory system) Pubic bone Urethra (excretory system) Shaft Glans Prepuce Labia minora Labia majora Clitoris

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Semen –Sperm, which are expelled through the ducts during ejaculation –Glandular secretions that carry, nourish, and protect the sperm Testes –Produce sperm –Located outside abdominal cavity within the scrotum 27.3 Reproductive anatomy of the human male

16. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.3B Bladder (excretory system) Prostate gland Bulbourethral gland Erectile tissue of penis Vas deferens Epididymis Testis Seminal vesicle (behind bladder) Urethra Scrotum Glans of penis

17. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.3A Seminal vesicle Rectum (digestive system) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum Bladder (excretory system) Pubic bone Erectile tissue of penis Urethra Glans of penis Prepuce

18. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings There are two stages of ejaculation –First stage of ejaculation Figure 27.3C Contractions of vas deferens Sphincter contracts Bladder Urethra region here expands and fills with semen Contractions of epididymis Sphincter contracts Contractions of prostate gland Contractions of seminal vesicle

19. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sphincter remains contracted Semen expelled Contractions of epididymis Sphincter relaxes Contractions of muscles around base of penis –Second stage of ejaculation (expulsion stage) Figure 27.3C

20. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Androgens stimulate sperm production –They also maintain homeostasis by a negative feedback mechanism that inhibits the secretion of FSH (follicle-stimulating hormone) and LH (luteinizing hormone)

21. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.3D Hypothalamus Anterior pituitary Stimuli from other areas in the brain Releasing hormone FSHLH Androgen production Testis Sperm production Negative feedback

22. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Spermatogenesis –Produces sperm in the male Oogenesis –Produces ova in the female 27.4 The formation of sperm and ova requires meiosis

23. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Spermatogenesis –Increases genetic variation –Primary spermatocytes are produced throughout a male’s reproductive years –Diploid cells undergo meiosis to form four haploid sperm

24. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.4A Testis Scrotum Epididymis Penis Testis Seminiferous tubule Cross section of seminiferous tubule Center of seminiferous tubule Diploid cell Differentiation and onset of MEIOSIS I PRIMARY SPERMATOCYTE (in prophase of MEIOSIS I ) MEIOSIS I completed SECONDARY SPERMATOCYTE (haploid; double chromatids) MEIOSIS II Developing sperm cells (haploid; single chromatids) Differentiation SPERM CELLS (haploid)

25. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Oogenesis –Most of the process occurs within the ovaries –Lifetime supply of primary oocytes is present at birth –One primary oocyte matures each month to form a secondary oocyte –If the secondary oocyte is fertilized, it completes meiosis and becomes a haploid ovum

26. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.4B Diploid cellIn embryo Differentiation and onset of MEIOSIS I arrested in prophase of MEIOSIS I Present at birth Completion of MEIOSIS I and onset of MEIOSIS II arrested at metaphase of MEIOSIS II ; released from ovary First polar body Entry of sperm triggers completion of MEIOSIS II (haploid) Second polar body PRIMARY OOCYTE, SECONDARY OOCYTE, OVUM

27. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Development of an ovarian follicle Figure 27.4C Start:PRIMARY OOCYTE within follicle Growing follicles Mature follicle Ovary Ruptured follicleOVULATION SECONDARY OOCYTE CORPUS LUTEUM Degenerating corpus luteum

28. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 27.5 Hormones synchronize cyclical changes in the ovary and uterus Table 27.5

29. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.5 (1) CONTROL BY HYPOTHALAMUS Inhibited by combination of estrogen and progesterone Stimulated by high levels of estrogen Hypothalamus Releasing hormone Anterior pituitary FSHLH (2) PITUITARY HORMONES IN BLOOD LH peak triggers ovulation and corpus luteum formation LH FSH LH

30. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.5 (continued) (3) OVARIAN CYCLE Growing follicle Mature follicle Ovulation Corpus luteum Degenerating corpus luteum Pre-ovulatory phase Post-ovulatory phase Estrogen Progesterone and estrogen (4) OVARIAN HORMONES IN BLOOD Estrogen Progesterone Estrogen Progesterone and estrogen (5) MENSTRUAL CYCLE Endometrium Menstruation Days

31. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Excitement –Sexual passion builds –Penis and clitoris become erect –Testes, labia, nipples swell –Vagina secretes lubricating fluid –Muscles of arms and legs tighten 27.6 The human sexual response occurs in four phases

32. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Plateau –Continuation of excitement responses –Increase in breathing and heart rates Orgasm –Rhythmic contraction of the reproductive structures –Extreme pleasure –Ejaculation by the male

33. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Resolution –Reverse previous phase responses –Structures return to normal size –Muscles relax –Passion subsides

34. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 27.7 Connection: Sexual activity can transmit disease Table 27.7

35. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Contraception prevents pregnancy in one of three ways –Blocking the release of gametes –Preventing fertilization –Preventing implantation 27.8 Connection: Contraception prevents unwanted pregnancy Figure 27.8

36. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 27.8

37. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The shape of a human sperm cell is adapted to its function 27.9 Fertilization results in a zygote and triggers embryonic development PRINCIPLES OF EMBRYONIC DEVELOPMENT Figure 27.9B Plasma membrane Tail Middle piece Neck Head Mitochondrion (spiral shape) Nucleus Acrosome

38. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Only one of these sperm will penetrate this human egg cell to initiate fertilization –Fertilization is the union of a sperm and an egg to form a diploid zygote Figure 27.9A

39. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Process of fertilization Figure 27.9C The sperm approaches the egg 1 2 3 4 The sperm’s acrosomal enzymes digest the egg’s jelly coat Proteins on the sperm head bind to egg receptors 5 The sperm nucleus enters the egg cytoplasm The plasma membranes of sperm and egg fuse 6 A fertilization envelope forms SPERM Nucleus Acrosome Plasma membrane Sperm head Acrosomal enzymes Jelly coat Vitelline layer Plasma membrane Cytoplasm EGG CELL Receptor protein molecules Sperm nucleus Egg nucleus 7 The nuclei of sperm and egg fuse Zygote nucleus

40. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cleavage is the first major phase of embryonic development –It is the rapid succession of cell divisions –It creates a multicellular embryo from the zygote –It partitions the multicellular embryo into developmental regions 27.10 Cleavage produces a ball of cells from the zygote

41. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cleavage in a sea urchin Figure 27.10 ZYGOTE 2 cells 4 cells 8 cells Many cells (solid ball) BLASTULA (hollow ball) Cross section of blastula Blastocoel

42. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gastrulation is the second major phase of embryonic development –It adds more cells to the embryo –It sorts all cells into three distinct cell layers –The embryo is transformed from the blastula into the gastrula 27.11 Gastrulation produces a three-layered embryo

43. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The three layers produced in gastrulation –Ectoderm, the outer layer –Endoderm, an embryonic digestive tract –Mesoderm, which partly fills the space between the ectoderm and endoderm

44. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Development of frog gastrula Animal pole Blastocoel 1 2 3 4 BLASTULAVegetal pole GASTRULATION Blastopore forming Blastocoel shrinking Archenteron Ectoderm Mesoderm Endoderm Yolk plug GASTRULA Figure 27.11C

45. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Embryonic tissue layers begin to differentiate into specific tissues and organ systems In chordates –the notochord develops from the mesoderm –the neural tube develops from the ectoderm The neural tube becomes the brain and spinal cord 27.12 Organs start to form after gastrulation

46. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.12A, B Archenteron Endoderm Mesoderm Ectoderm Notochord Neural fold Neural plate Neural folds Neural fold Neural plate Outer layer of ectoderm Neural tube

47. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Somites are blocks of mesoderm that will give rise to segmental structures The body cavity, or coelom, also develops from the mesoderm Figure 27.12C Neural tube Notochord Coelom Somite Archenteron (digestive cavity) SomitesTail bud Eye

48. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 27.12

49. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The tissues and organs of a tadpole emerge from cells of the ectoderm, mesoderm, and endoderm Figure 27.12D

50. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Tissues and organs take shape in a developing embryo as a result of –cell shape changes –cell migration 27.13 Changes in cell shape, cell migration, and programmed cell death give form to the developing animal Figure 27.13A Ectoderm

51. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –programmed cell death (apoptosis) Figure 27.13B Cell suicide Dead cell engulfed and digested by adjacent cell

52. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Induction is the mechanism by which one group of cells influences the development of tissues and organs from ectoderm, endoderm, and mesoderm –Adjacent cells and cell layers use chemical signals to influence differentiation –Chemical signals turn on a set of genes whose expression makes the receiving cells differentiate into a specific tissue 27.14 Embryonic induction initiates organ formation

53. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Induction during egg development Figure 27.14 Lens ectoderm Future brain Optic vesicle Optic cup Optic stalk 1234 Cornea Lens Future retina

54. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pattern formation is the emergence of a body form with structures in their correct relative positions –It involves the response of genes to spatial variations of chemicals in the embryo 27.15 Pattern formation organizes the animal body

55. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Wing development Figure 27.15A Bird embryo ANTERIOR VENTRAL DISTAL PROXIMAL POSTERIOR DORSAL Limb bud Limb bud develops Normal wing

56. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pattern-forming zone Figure 27.15B Donor limb bud Graft of cells from pattern- forming zone Donor cells Host limb bud Host pattern- forming zone Host limb bud develops Wing with duplication Graft

57. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gestation is pregnancy –It begins at conception and continues until birth –Human gestation is 266 days (38 weeks or 9 months) –Mouse gestation is 1 month –Elephant gestation is 22 months 27.16 The embryo and placenta take shape during the first month of pregnancy HUMAN DEVELOPMENT

58. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Human development begins with fertilization in the oviduct Figure 27.16A Cleavage starts Fertilization of ovum Oviduct Secondary oocyte Ovulation Ovary Blastocyst (implanted) Endometrium Uterus

59. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cleavage produces a blastocyst –A blastocyst is a fluid-filled cavity –The inner cells of the blastocyst form the baby –The outer cells form the embryo trophoblast Figure 27.16B ENDOMETRIUM Inner cell mass Cavity Trophoblast

60. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The trophoblast secretes enzymes to enable the blastocyst to implant in the uterine wall Figure 27.16C ENDOMETRIUM Future embryo Future yolk sac Multiplying cells of trophoblast Trophoblast UTERINE CAVITY Blood vessel (maternal)

61. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gastrulation occurs and organs develop from the ectoderm, endoderm, and mesoderm Figure 27.16D Mesoderm cells Amniotic cavity Amnion Chorion Yolk sac

62. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Meanwhile, the four embryonic membranes develop –Amnion –Chorion –Yolk sac –Allantois Figure 27.16E Chorion Amnion Allantois Yolk sac Chorionic villi EMBRYO: Ectoderm Mesoderm Endoderm

63. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The embryo floats in the fluid-filled amniotic cavity, while the chorion and embryonic mesoderm form the embryo’s part of the placenta The placenta’s chorionic villi absorb food and oxygen from the mother’s blood Figure 27.16F Placenta Allantois Yolk sac Mother’s blood vessels Amniotic cavity Amnion Embryo Chorion Chorionic villi

64. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The placenta allows for a variety of substances to pass from mother to fetus –Protective antibodies –German measles virus –HIV –Drugs (prescription and nonprescription) –Alcohol –Chemicals in tobacco smoke

65. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings First trimester –First three months –The most rapid changes occur during the first trimester 27.17 Human development from conception to birth is divided into three trimesters Figure 27.17A, B

66. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Second trimester –Increase in size of fetus –General refinement of human features Figure 27.17C, D

67. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Third trimester –Growth and preparation for birth Figure 27.17E

68. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hormonal changes induce birth –Labor is controlled by a positive feedback mechanism –Estrogen released from the ovaries increases the sensitivity of the uterus to oxytocin 27.18 Childbirth is hormonally induced and occurs in three stages

69. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Oxytocin is a powerful stimulant for the smooth muscles of the uterus –Oxytocin also stimulates the placenta to make prostoglandins that stimulate the uterine muscles to contract even more Uterine contractions stimulate the release of more and more oxytocin and prostoglandins

70. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 27.18A ESTROGENOXYTOCIN from ovaries From fetus and pituitary Induces oxytocin receptors on uterus Stimulates uterus to contract Stimulates placenta to make PROSTAGLANDINS Stimulates more contractions of uterus Positive feedback

71. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings There are three stages of labor Dilation of the cervix is the first stage –Cervix reaches full dilation at 10cm –Longest stage of labor (6-12 hours or longer) Figure 27.18B, part 1 Dilation of the cervix 1 Placenta Umbilical cord Uterus Cervix

72. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Expulsion is the second stage –Period from full dilation of the cervix to delivery of the infant –Uterine contractions occur every 2-3 minutes –Mother feels urge to push down with her abdominal muscles –Infant is forced down and out of uterus and vagina within a period of 20 minutes Figure 27.18B, part 2 Expulsion: delivery of the infant 2

73. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The delivery of the placenta is the final stage of labor –Usually occurs within 15 minutes after the birth of the baby Figure 27.18B, part 3 Delivery of the placenta 3 Umbilical cord Uterus Placenta (detaching)

74. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hormones continue to be important after the baby and placenta are delivered –Decreasing progesterone and estrogen levels allow the uterus to return to its pre-pregnancy state –Oxytocin and prolactin stimulate milk secretion

75. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Reproductive technology –Hormone therapy can increase sperm or egg production –Surgery can correct blocked oviducts Assisted reproductive technology –In vitro fertilization (IVF) Surrogate motherhood 27.19 Connection: Reproductive technology increases our reproductive options Figure 27.19