Sexual Reproduction

1. Sexual Reproduction involves 2 parents Involves the process of meiosis Variety in the offspring

2. Background Vocabulary: - gametes – sex cells – sperm and egg - gonads – sex organs/glands – testes and ovaries - zygote – fertilized egg egg + sperm = zygote - meiosis – process by which sex cells develop - gametogenesis - diploid (2n) – normal # of chromosomes (46 – human) all cells except sperm and egg - monoploid (n) – ½ the # of chromosomes (23 – human) only sperm and egg

5. Meiosis – results: 4 daughter cells with ½ the number of chromosomes

6. B Meiosis – result 4 daughter cells ½ the # of chromosomes

8. Meiosis 2 major divisions Still double stranded – splits again

9. Meiosis: cell division – making sex cells – gametes – sperm/egg - occurs in sex organs (gonads- testes and ovaries) Gametogenesis = meiosis monoploid diploid diploid Result: 4 daughter cells with ½ the # of chromosomes

10. Homologous Chromosomes – pair of chromosomes dealing with the same characteristics – one from mom and one from Dad – makes a tetrad (4strands)

11. During meiosis, crossing over may occur  parts of chromatid strands actually exchange segments  this increases variety. Tetrads – homologous chromosomes paired up

12. Gamete Formation Spermatogenesis - testes produce sperm - diploid cell  meiosis  4 monoploid cells - each usually matures into a motile sperm cell

13. Result 4 motile sperm – 4/4

14. Oogenesis - ovaries produce eggs (ovum/ova) - ovum: larger, non-motile - only 1 monoploid ovum usually forms - other 3 – polar bodies – die - unequal cytoplasmic division

15. Result: 1 egg and 3 polar bodies

16. Spermatogenesis Oogenesis

17. Hermaphrodite – an organism with functional male and female gonads. Ex. earthworm

18. Zygote Formation - zygote fertilized egg - sperm + egg = zygote (fertilized egg) - process is called fertilization - recombination occurs - chromosomes from both parents recombine – increases variety

19. Zygote Formation • YouTube - Medical animation of egg fertilization

20. Fertilization Zygote Cleavage

21. Mitosis – Cleavage All cells exactly the same – for now!

22. Embryonic development • YouTube - Amphioxus embryonic development YouTube - human development

23. Embryo Formation - the zygote divides by mitosis (cleavage) to form an embryo - differentiation occurs cells become different - take on their own identity(hair cell, skin cell, etc.) – DNA does not change the cell just uses different parts of the DNA**** - zygote  embryo – divisions by mitosis - process is gastrulation – process of indenting

24. In one individual – same DNA in all the cells…these cells look different and do different jobs…Why? They simply use different parts of that DNA

25. Embryo Formation – zygote morula(solid ball)  blastula (hollow ball)  gastrula (3 germ layers – endoderm ectoderm mesoderm)

27. Fertilization Cleavage mitosis Sperm + egg = zygote

30. Internal Fertilization - fertilization occurs inside the female - usually terrestrial (land) organisms - few eggs produced - protected - could have either internal (mammals) or external (birds/reptiles) development External Fertilization - fertilization occurs outside the body of the female - usually aquatic (water) organisms - many eggs – ensure survival - only external development Examples – fish, amphibians

31. Male reproductive system • Sperm production • over 100 million produced per day! • ~2.5 million released per drop!

32. Male Reproductive System

33. Male Reproductive System 2 major functions: 1. Make sperm 2. Deposit in female (internal fertilization) Structures and Functions: • Testes: Male gonads • Sperm and testosterone production • Location  scrotum – keeps sperm 1 – 2 degreescooler than normal body temperature

34. 2. Vas Deferens: a. tube that connects testes to urethra b. sperm transported here c. along the way secretions from 3 glands are picked up to make semen. 3. Semen: sperm + fluids 4. Testosterone: hormone secreted by testes, regulates development of secondary sex characteristics.

35. Male Reproductive System – Frontal View

36. Male Reproductive System

37. Female Reproductive System

38. Female reproductive system

39. Female reproductive system

40. Female Reproductive System Structures and Functions • Ovaries: a. female gonads b. produce eggs (meiosis – oogenesis) c. eggs enclosed in follicles d. once a month egg is ovulated (released – into fallopian tube) 2. Fallopian Tubes (oviducts): a. connects ovary to uterus b. fertilization here

41. 3. Uterus: a. implantation here (embryo embeds itself into uterine wall) b. development from embryo to fetus here 4. Vagina: a. birth canal (menstruate through here too) 5. Estrogen and progesterone: a. female hormones (ovaries) b. regulate secondary sex characteristics c. menstrual cycle

42. Fertilization

45. Menstrual Cycle Background information: • series of changes in ovaries and uterus • Begins at puberty • Temporarily stops during pregnancy • Menopause – cycle stops permanently

46. Stages of the Menstrual Cycle

47. Stages of the Menstrual Cycle (Lasts about 28 days) • Stage 1: Follicle Stage (10 days) • Pituitary  FSH • Egg matures in follicle – swells • Ovaries  estrogen – thickens uterus B. Stage 2: Ovulation (stays in tube 2 – 3 days) a. Pituitary  LH b. egg released from follicle

48. Egg maturation in ovary releasesprogesterone maintainsuteruslining produces estrogen

49. Stage 3: Corpus Luteum Stage (~ 14 days) • Follicle dies – forms a “scar”  corpus luteum • Corpus luteum (ovary)  progesterone • Causes uterine lining to stay thick • Stage 4: Menstruation (4 days) a. egg not fertilized – uterine lining breaks down

50. corpusluteum ovary yes corpusluteum no Feedback Female reproductive cycle eggmatures & is released(ovulation) builds up uterus lining estrogen progesterone FSH & LH fertilized egg(zygote) maintainsuterus lining HCG pituitarygland pregnancy progesterone GnRH corpus luteum breaks down progesterone drops menstruation maintainsuterus lining hypothalamus