1. Bellwork Why do you think sex (exchange of gametes) has evolved? In what conditions do you think organisms would favor asexual versus sexual reproduction, and visa versa? Something to think about: Sexual females have half as many daughters as asexual females; this is the “twofold cost” of sexual reproduction

2. Fig. 46-3 Asexual reproduction Female Sexual reproduction Female Generation 1 Male Generation 2 Generation 3 Generation 4

3. Sexual reproduction results in genetic recombination, which provides potential advantages: ▫Increase in variation in offspring  increase in the reproductive success in changing environments  An increase in the rate of adaptation  A shuffling of genes and the elimination of harmful genes from a population

4. Sexual reproduction is the creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote Asexual reproduction is creation of offspring without the fusion of egg and sperm

5. Asexual In budding, new individuals arise from outgrowths of existing ones Fragmentation is breaking of the body into pieces, some or all of which develop into adults ▫Fragmentation must be accompanied by regeneration, regrowth of lost body parts Parthenogenesis is the development of a new individual from an unfertilized egg

6. Human Reproductive system

7. 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 Endometriu m Vagina

8. Each ovary contains many follicles, which consist of a partially developed egg (oocyte) Once a month, an oocyte develops into an ovum (egg) by the process of oogenesis Ovulation expels an egg cell from the follicle

10. The egg cell travels from the ovary to the uterus via an oviduct, or fallopian tube Cilia in the oviduct convey the egg to the uterus, also called the womb

11. Fig. 46-11 Seminal vesicle (behind bladder) (Urinary bladder) Prostate gland Bulbourethra l 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 Prepuc e Penis

12. The male gonads, or testes, consist of highly coiled tubes surrounded by connective tissue Sperm form in these seminiferous tubules Production of normal sperm cannot occur at the body temperatures of most mammals

13. Semen is composed of sperm plus secretions from three sets of accessory glands The two seminal vesicles contribute about 60% of the total volume of semen ▫Contains fructose providing energy for the sperm and coagulating enzymes The prostate gland secretes its products directly into the urethra through several small ducts ▫Contains anticoagulant and citrate (sperm nutrient) The bulbourethral glands secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra ▫As well as some semen – this is why the withdrawal method of birth control is very ineffective

14. Fig. 46-11b Seminal vesicle (Rectum) Vas deferens Ejaculatory duct Prostate gland Bulbourethral gland Vas deferens Epididymis Testis Scrotum (Urinary bladder) (Urinary duct) (Pubic bone) Erectile tissue Urethr a Glans Prepuce Penis

15. 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

16. 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 Spermatogoniu m Primary spermatocyte Meiosis I Meiosis II Secondary spermatocyte Lumen of seminiferous tubule Plasma membrane Tai l Neck Midpiec e Hea d Mitochondria Nucleus Acrosome Spermatids (at two stages of differentiation ) Early spermatid Differentiation (Sertoli cells provide nutrients) Sperm 2n2n 2n2n 2n2n nn nnnn n n n n

17. Eggs contain stored nutrients and are much larger Oogenesis is development of mature oocytes (eggs) and can take many years

18. Fig. 46-12e Ovary In embryo Primordial germ cell Mitotic divisions Oogoniu m Mitotic divisions Primary oocyte (present at birth), arrested in prophase of meiosis I First polar body Completion of meiosis I and onset of meiosis II Secondary oocyte, arrested at metaphase of meiosis II Ovulation, sperm entry Completion of meiosis II Second polar body Fertilized egg Primary oocyte within follicle Growing follicle Mature follicle Ruptured follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum 2n2n 2n2n n n n n

19. Sex Hormones FSH and LH regulate processes in the gonads and the production of sex hormones The sex hormones are androgens, estrogens, and progesterone Females – mainly estrogens and progestrone Male – mainly androgens (testosterone)

20. Male Hormones FSH and LH regulate cells which control sperm production

21. Female Hormones In females, the secretion of hormones and the reproductive events they regulate are cyclic

24. Fertilization Sperm can live up to 5 days in the reproductive tract The Egg can live 24-48 hours after being released

25. Conception, fertilization of an egg by a sperm, occurs in the oviduct The resulting zygote begins to divide by mitosis in a process called cleavage Division of cells gives rise to a blastocyst, a ball of cells with a cavity

26. The embryo releases human chorionic gonadotropin (hCG), which prevents menstruation ▫This is what pregnancy tests detect

27. First trimester Embryo gets nutrients from the endometrium ▫Diffuses nutrient, immune protection, respiratory gasses and releases waste ▫Splitting of the embryo can develop into monozygotic twins (genetically identicle)  Dizygotic twins – two eggs fertilized independently ▫Organogenesis – development of body organs

28. Second trimester Placenta takes over hormone levels (progesterone)

29. Third trimester Growth of the fetus