Reproduction 1

1. Reproduction 1 Chapter 6.6

2. Explain the advantages of sexual reproduction. • Sexual reproduction causes a shuffling of genes in each generation. This provides diversity for adaptation should the environment change. • The investment is worth it if one offspring is able to survive because of a new combination of genetic traits.

3. 6.6.1 Draw and label diagram of the adult male and female reproductive systems. • To be done in class

4. The menstrual cycle • Each cycle lasts ~28 days • Purpose is to time the release of an egg for possible fertilization and implantation • If fertilization and implantation don’t occur, the highly vascular endometrium breaks down = menstruation • Menstruation is a sign that no pregnancy occurred

5. 6.6.2 Outline the role of hormones in the menstrual cycle, including FSH, LH, estrogen and progesterone. FSH (follicle stimulating hormone) LH (luteinizing hormone) • Target the ovaries • Effects: • Increase production and secretion of estrogen • Stimulate follicle cells and oocytes to become Graafian follicles • Causes ovulation (release of oocyte from Graafian follicle)

6. 6.6.2 Outline the role of hormones in the menstrual cycle, including FSH, LH, estrogen and progesterone. Estrogen • target tissue is the endometrium • endometrium becomes highly vascular Progesterone • maintains the thickened, highly vascular endometrium http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__positive_and_negative_feedback__quiz_2_.html

7. The menstrual cycle • GnRH stimulates the anterior pituitary to secrete FSH & LH • FSH stimulates the immature follicles in the ovary secrete small amounts of estrogen • As estrogen secretion increases, the follicle continues to grow and secrete more estrogen (positive feedback!) • High amount of estrogen stimulates the hypothalamus to increase GnRH which makes an increase in FSH and LH secretion • Increased LH stimulates final maturation of the follicle and ovulation

8. The menstrual cycle • LH during the luteal phase stimulates the corpus luteum (remaining follicular tissue that grows within the ovary to form a solid mass) to continue secreting estrogen but also progesterone • Increasing estrogen and progesterone inhibits GnRH secretion by the hypothalamus, which results in decrease in FSH and LH • As LH declines, the corpus luteum begins to atrophy; results in sudden drop in estrogen and progesterone • Decreasing estrogen and progesterone removes the inhibition exerted on the hypothalamus, which begins to secrete small amounts of GnRH that stimulates the anterior pituitary to secrete low levels of FSH and LH • A new follicular phase begins at this point

9. 6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and thickening of the endometrium.

10. 6.6.4 List three roles of testosterone in males. • Determines the development of male genitalia during embryonic development • Ensures development of secondary sex characteristics during puberty • Maintain the sex drive of males throughout their lifetime

11. 6.6.5 Outline the process of in-vitro fertilization (IVF). • Used if couples are unable to bear children (due to low sperm count, impotence, irregular ovulation, blocked Fallopian tubes • Hormones stimulate many eggs to mature at once • Eggs removed from ovary • Eggs are fertilized in culture dishes • Embryo is put in uterus to implant, then pregnancy continues as normal 

12. 6.6.6 Discuss the ethical issues associated with IVF. • In favor • able to have children • can screen embryos before implantation • Against • infertility may be passed on • more embryos produced than needed • embryos are ‘chosen’ • multiple births more likely