Animal Reproduction

1. Animal Reproduction

2. Sexual & asexual reproduction • Asexual • offspring all have same genes (clones) • no variation • Sexual • gametes (sperm & egg)  fertilization • mixing of genes  variation

3. Parthenogenesis • Development of an unfertilized egg • honey bees • drones = males produced through parthenogenesis  haploid • workers & queens = females produced from fertilized eggs  diploid queen worker drone

4. Different strokes… gay penguins parthenogenesis in aphids “lesbian” lizards sex-change in fish

5. Hermaphrodites • Having functional reproductive system of both sexes earthworms mating flat worm

6. Fertilization • Joining of egg & sperm • external • usually aquatic animals • internal • usually land animals

7. Development • External • development in eggs • fish & amphibians in water • soft eggs= exchange across membrane • birds & reptiles on land • hard-shell amniotic eggs • structures for exchange of food, O2 & waste • sharks & some snakes • live births from eggs • Internal • placenta • exchange food & waste • live birth

8. Adaptive advantages? • What is the adaptive value of each type of sexual reproduction • number of eggs? • level of parental of care • habitat?

9. Human Reproduction

10. Reproductive hormones LH &FSH • Testosterone • from testes • functions • sperm production • 2° sexual characteristics • Estrogen • from ovaries • functions • egg production • prepare uterus for fertilized egg • 2° sexual characteristics testesorovaries

11. Sex hormone control in males Hypothalamus GnRH Pituitary FSH & LH Testes testosterone Body cells

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

13. Male reproductive system • Testicles • produces sperm & hormones • Scrotum • sac that holds testicles outside of body • Epididymis • where sperm mature • Vas deferens • tubes for sperm to travel from testes to penis • Prostate, seminal vesicles, Cowper’s (bulbourethal) glands • nutrient rich fluid to feed & protect sperm • buffer to counteract acids in vagina

14. seminiferous tubule Male reproductive system • Testes & epididymis • sperm production & maturation • Glands • seminal vesicles, prostate, bulbourethal • produce seminal fluid = nutrient-rich sperm spermatocytes

15. Spermatogenesis Testis Epididymis Germ cell (diploid) Coiled seminiferous tubules 1° spermatocyte (diploid) MEIOSIS I 2° spermatocytes (haploid) MEIOSIS II Vas deferens Spermatids (haploid) Spermatozoa Cross-section of seminiferous tubule

16. Female reproductive system

17. Female reproductive system • Ovaries • produces eggs & hormones • Uterus • nurtures fetus; lining builds up each month • Fallopian tubes • tubes for eggs to travel from ovaries to uterus • Cervix • opening to uterus, dilates 10cm (4 inches) for birthing baby • Vagina • birth canal for birthing baby

18. Female reproductive system

19. LH Menstrual cycle FSH Hypothalamus egg development ovulation = egg release GnRH corpus luteum Pituitary FSH & LH estrogen progesterone Ovaries lining of uterus estrogen Body cells days 0 7 14 21 28

20. Egg maturation in ovary • Corpus luteum • produces progesterone to maintain uterine lining

21. Female hormones • FSH & LH • release from pituitary • stimulates egg development & hormone release • peak release = release of egg (ovulation) • Estrogen • released from ovary cells around developing egg • stimulates growth of lining of uterus • lowered levels = menstruation • Progesterone • released from “corpus luteum” in ovaries • cells that used to take care of developing egg • stimulates blood supply to lining of uterus • lowered levels = menstruation

22. Oogenesis • What is the advantage of this development system? Meiosis 1 completed during egg maturation ovulation Meiosis 2 completed triggered by fertilization

23. Fertilization

24. Fertilization • Joining of sperm & egg • sperm head enters egg

25. Cleavage • Repeated mitotic divisions of zygote • 1st step to becoming multicellular • unequal divisions establishes body plan • different cells receive different portions of egg cytoplasm & therefore different regulatory signals

26. Cleavage • zygote  morula  blastula • establishes future development

27. Gastrulation • Establish 3 cell layers • ectoderm • outer layers • skin, nails, teeth, nerves • mesoderm • blood, bone & muscle • endoderm • inner lining • digestive system ectoderm mesoderm endoderm

28. Neural groove Notochord Neurulation • 1st organ to form is notochord & nerve chord • develop into nervous system Neural tube

29. Organogenesis Umbilical blood vessels Mammalian embryo Chorion Bird embryo Amnion Yolk sac Allantois Fetal blood vessels Placenta Maternal blood vessels

30. Placenta • Materials exchange across membranes

31. Human fetal development 4 weeks 7 weeks

32. Sex determination Zygote Sperm Develop in early embryo Y Testes XY Ovum X SRY Seminiferous tubules Indifferent gonads Leydig cells No SRY X Ovaries Ovum XX (Follicles do not develop until third trimester) X Sperm Zygote

33. Human fetal development 10 weeks

34. Human fetal development 12 weeks 20 weeks

35. Human fetal development • The fetus just spends much of the 2nd & 3rd trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid Week 20

36. Human fetal development • 24 weeks (6 months; 2nd trimester) fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix

37. Human fetal development • 30 weeks (7.5 months) umbilical cord

38. Getting crowded in there!! • 32 weeks (8 months) The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming

39. Hormone induction Birth positive feedback

40. Birth (36 weeks) Intestine Placenta Umbilical cord Wall of uterus Bladder Cervix Vagina

41. The end of the journey!