Chapter 59

Summary		Questions		Media Resources
59.1 Animals employ both sexual and asexual reproductive strategies.
• Parthenogenesis is a form of asexual reproduction that is practiced by many insects and some lizards. • Among mammals, the sex is determined by the presence of a Y chromosome in males and its absence in females.		1.  How are oviparity, ovoviviparity, and viviparity different?
59.2 The evolution of reproduction among the vertebrates has led to internalization of fertilization and development.
• Most bony fish practice external fertilization, releasing eggs and sperm into the water where fertilization occurs. Amphibians have external fertilization and the young go through a larval stage before metamorphosis. • Reptiles and birds are oviparous, the young developing in eggs that are deposited externally. Most mammals are viviparous, the young developing within the mother.		2.  How does fetal development differ in the monotremes, marsupials, and placental mammals?		•Reproductive Biology of House Mice • Evolution of Uterine Function
59.3 Male and female reproductive systems are specialized for different functions.
• Sperm leave the testes and pass through the epididymis and vas deferens; the ejaculatory duct merges with the urethra, which empties at the tip of the penis. • An egg cell released from the ovary in ovulation is drawn by fimbria into the fallopian tube, which conducts the egg cell to the lining of the uterus, or endometrium, where it implants if fertilized. • If fertilization does not occur, the corpus luteum regresses at the end of the cycle and the resulting fall in estradiol and progesterone secretion cause menstruation to occur in humans and apes.		3.  Briefly describe the function of the seminal vesicles, prostate gland, and bulbourethral glands. 4.  When do the ova in a female mammal begin meiosis? When do they complete the first meiotic division? 5.  What hormone is secreted by the granulosa cells in a Graafian follicle? What effect does this hormone have on the endometrium?		•Male Reproductive System •Penis Anatomy A •Penis Anatomy B •Female Reproductive System •Breast Anatomy •Spermatogenesis •Menstruation •Female Reproductive Cycle •Oogenesis •Introduction to Reproduction •Human Male System •Human Female System •Hormonal Control of Male Reproduction •Mammalian Uteruses •Human Menstrual Cycle •Hormones and Multiple Births •Artificial Womb
59.4 The physiology of human sexual intercourse is becoming better known.
• The physiological events that occur in the human sexual response are grouped into four phases: excitement, plateau, orgasm, and resolution. • Males and females have similar phases, but males enter a refractory period following orgasm that is absent in many women. • There are a variety of methods of birth control available that range in ease of use, effectiveness, and permanence.		6.  What are the four phases in the physiological events of sexual intercourse in humans? During the first phase, what events occur specifically in males, and what events occur specifically in females? 7.  How do birth control pills prevent pregnancy?		•Penile Erection •Vasectomy •Tubal Ligation •Birth Control

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