How can each of these earthworms be both male and female? Figure 46.1 How can each of these earthworms be both male and female?

Asexual reproduction of a sea anemone Figure elegantissima)

The “reproductive handicap” of sex: Sexual females have half as many daughters as asexual females. Asexual reproduction Sexual reproduction Female Generation 1 Female Generation 2 Male Generation 3 Figure Generation 4

External fertilization Figure Eggs

Parental care in an invertebrate Figure 46.6

Most insects have separate sexes with complex reproductive systems. In many insects, the female has a spermatheca in which sperm is stored during copulation. Accessory gland Ovary Ejaculatory duct Testis Oviduct Spermatheca Penis Vas deferens Vagina Seminal vesicle Accessory gland Figure 46.7 Insect reproductive anatomy (a) Male honeybee (drone) (b) Female honeybee (queen)

Ovary Testis Reproductive anatomy of a hermaphrodite (Digestive tract) Genital pore Male organs: Female organs: Uterus Yolk gland 4 Seminal vesicle 3 Yolk duct 3 Sperm duct (vas deferens) 2 Oviduct 1 Ovary Figure 46.8 Reproductive anatomy of a hermaphrodite 2 Vas efferens Seminal receptacle 1 Testis (Excretory pore)

Reproductive anatomy of the human female Oviduct Ovary Uterus (Urinary bladder) (Rectum) (Pubic bone) Cervix Urethra Vagina Shaft Glans Clitoris Prepuce Labia minora Labia majora Vaginal opening Oviduct Ovaries Figure 46.10 Follicles Corpus luteum Uterine wall Uterus Endometrium Cervix Vagina

Reproductive anatomy of the human male Seminal vesicle (behind bladder) (Urinary bladder) Prostate gland Bulbourethral gland Urethra Erectile tissue of penis Scrotum Vas deferens Epididymis Testis (Urinary bladder) (Urinary duct) Figure 46.11 Seminal vesicle (Rectum) (Pubic bone) Vas deferens Erectile tissue Ejaculatory duct Prostate gland Urethra Bulbourethral gland Penis Glans Vas deferens Epididymis Testis Scrotum Prepuce

Spermatogenesis Figure 46.12 Human gametogenesis Epididymis Seminiferous tubule Testis Cross section of seminiferous tubule Primordial germ cell in embryo Mitotic divisions Sertoli cell nucleus Spermatogonial stem cell 2n Mitotic divisions Spermatogonium 2n Mitotic divisions Primary spermatocyte 2n Meiosis I Figure 46.12 Human gametogenesis For the Cell Biology Video Motion of Isolated Flagellum, go to Animation and Video Files. For the Cell Biology Video Flagellum Movement in Swimming Sperm, go to Animation and Video Files. Lumen of seminiferous tubule Secondary spermatocyte n n Meiosis II Neck Spermatids (at two stages of differentiation) Early spermatid n n n n Tail Midpiece Head Plasma membrane Differentiation (Sertoli cells provide nutrients) Mitochondria Sperm n n n n Nucleus Acrosome

Mature sperm Figure 46.12 Human gametogenesis Neck Tail Midpiece Head Plasma membrane Mitochondria Nucleus Acrosome Figure 46.12 Human gametogenesis

Oogenesis Figure 46.12 Human gametogenesis 2n 2n n n n n Ovary Primary oocyte within follicle In embryo Growing follicle Primordial germ cell Mitotic divisions 2n Oogonium Mitotic divisions Primary oocyte (present at birth), arrested in prophase of meiosis I 2n Mature follicle Ruptured follicle Completion of meiosis I and onset of meiosis II First polar body Figure 46.12 Human gametogenesis n n Secondary oocyte, arrested at metaphase of meiosis II Ovulated secondary oocyte Ovulation, sperm entry Completion of meiosis II Second polar body Corpus luteum n n Fertilized egg Degenerating corpus luteum

Testis Hormonal control in the Male – – – Hypothalamus GnRH Anterior pituitary FSH LH Negative feedback Negative feedback Sertoli cells Leydig cells Figure 46.13 Inhibin Spermatogenesis Testosterone Testis

Degenerating corpus luteum The reproductive cycle of the human female (a) Control by hypothalamus Inhibited by combination of estradiol and progesterone Hypothalamus – Stimulated by high levels of estradiol 1 GnRH + Anterior pituitary Inhibited by low levels of estradiol – 2 FSH LH (b) Pituitary gonadotropins in blood 6 LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation 3 (c) Ovarian cycle 7 8 Growing follicle Maturing follicle Corpus luteum Degenerating corpus luteum Follicular phase Ovulation Luteal phase Estradiol secreted by growing follicle in increasing amounts Progesterone and estradiol secreted by corpus luteum 4 (d) Ovarian hormones in blood Peak causes LH surge 5 Figure 46.14 10 Estradiol Progesterone 9 Estradiol level very low Progesterone and estra- diol promote thickening of endometrium (e) Uterine (menstrual) cycle Endometrium Menstrual flow phase Proliferative phase Secretory phase Days | | | | | | | | 5 10 14 15 20 25 28

(a) From ovulation to implantation 3 Cleavage Cleavage continues 4 Ovary 2 Fertilization Uterus The blastocyst implants 5 1 Ovulation (a) From ovulation to implantation Endometrium Figure 46.15 Formation of the zygote and early post-fertilization events Endo- metrium Inner cell mass Cavity Trophoblast Blastocyst (b) Implantation of blastocyst

Placental circulation Maternal arteries Maternal veins Placenta Maternal portion of placenta Umbilical cord Chorionic villus, containing fetal capillaries Fetal portion of placenta (chorion) Maternal blood pools Figure 46.16 Uterus Umbilical arteries Fetal arteriole Fetal venule Umbilical cord Umbilical vein

Human fetal development Figure 46.17 (a) 5 weeks (b) 14 weeks (c) 20 weeks

from fetus and mother’s posterior pituitary Labor Estradiol Oxytocin + from ovaries from fetus and mother’s posterior pituitary Induces oxytocin receptors on uterus Positive feedback Stimulates uterus to contract Stimulates placenta to make + Figure 46.18 A model for the induction of labor Prostaglandins Stimulate more contractions of uterus

The three stages of labor Placenta Umbilical cord Uterus Cervix Dilation of the cervix 1 Expulsion: delivery of the infant Figure 2 Uterus Placenta (detaching) Umbilical cord Delivery of the placenta 3

Mechanisms of several contraceptive methods Male Female Method Event Event Method Production of sperm Production of primary oocytes Vasectomy Combination birth control pill (or injection, patch, or vaginal ring) Sperm transport down male duct system Oocyte development and ovulation Abstinence Abstinence Condom Female condom Coitus interruptus (very high failure rate) Sperm deposited in vagina Capture of the oocyte by the oviduct Tubal ligation Spermicides; diaphragm; cervical cap; progestin alone (as minipill, implant, or injection) Sperm movement through female reproductive tract Transport of oocyte in oviduct Figure 46.20 Meeting of sperm and oocyte in oviduct Morning-after pill; intrauterine device (IUD) Union of sperm and egg Implantation of blastocyst in endometrium

Gametogenesis Spermatogenesis Oogenesis n n n n n n n n n n n n n n Primary spermatocyte Primary oocyte 2n 2n n Polar body Secondary spermatocytes Secondary oocyte n n n n n n n Spermatids n n n n Sperm n Polar body Fertilized egg n

You should now be able to: Distinguish between asexual and sexual reproduction. Explain how hermaphroditism may be advantageous to animals that have difficulty encountering a member of the opposite sex. Describe various ways in which animals may protect developing embryos. Using diagrams, identify and state the function of each component of the male and female reproductive systems.

Describe oogenesis and spermatogenesis; describe three major differences between them. Explain how the uterine and ovarian cycles are synchronized and describe the functions of the hormones involved. List the various methods of contraception, how each works. Describe techniques that allow us to learn about the health and genetics of a fetus.