Animal Reproduction & Development

1. Animal Reproduction&Development

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

3. Parthenogenesis • Egg development without a male contribution • Wasps, honeybees, aphids, komodo dragons, some fish, frogs and lizards • Usually produces males

4. Mechanisms of sexual reproduction • Fertilization(union of sperm and egg) • external • internal • Timing • Compatible copulatory organs • All species produce more offspring than the environment can handle • Survival??? • Pheromones • chemical signals that influence the behavior of others (mate attractants)

5. 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

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

7. Testicle (seminiferous tubules) Male reproductive system sperm • Testes & epididymis • sperm production & maturation • Sperm production • over 100 million produced per day! • ~2.5 million released per drop! • Glands • seminal vesicles, prostate, bulbourethal • produce seminal fluid = nutrient-rich (sugars) spermatocytes

8. Spermatogenesis Produce semen by age 7 Produce sperm by puberty (11-14 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

9. Female reproductive system

10. 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

11. Menstrual cycle LH 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

12. Female hormones • FSH & LH • release from pituitary • stimulates egg development (follicle) & 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

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

14. release Oogenesis • Unequal meiotic divisions • unequal distribution of cytoplasm • 1 egg • 2 polar bodies Cell stored in ovaries Meiosis 1 completed during egg maturation Cell matures in follicle on ovary ovulation Meiosis 2 completed triggered by fertilization

15. Fertilization • fertilization • Cleavage • Morula • Blastocyst • Implantation • gastrulation • neurulation • Organogenesis • Fetus

16. Fertilization • Joining of sperm & egg • sperm head (nucleus) enters egg • Acrosome (enzyme filled vesicle)

18. 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

19. Cleavage • zygote  morula  blastula • establishes future development zygote gastrulation blastula morula

20. Gastrulation gastrulation inprimitive chordates • Establish 3 cell layers • ectoderm • outer body tissues • skin, nails, teeth • nerves, eyes, lining of mouth • mesoderm • middle tissues • blood & lymph, bone & notochord, muscle • excretory & reproductive systems • endoderm • inner lining • digestive system • lining of respiratory, excretory & reproductive systems ectoderm mesoderm endoderm

21. Neurulation • Formation of notochord & neural tube • develop into nervous system develops into CNS (brain & spinal cord) Neural tube Notochord develops intovertebral column

22. Organogenesis • Organ development and differentiation from germ layers

23. Placenta • Materials exchange across membranes

24. Human fetal development 4 weeks 7 weeks

25. Human fetal development 10 weeks

26. Human fetal development 12 weeks 20 weeks

27. 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

28. 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

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

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

31. Fetal slide notes

32. Apoptosis • Programmed cell death • Sculpts body parts • Genetically programmed elimination of tissues & cells that were used for only short periods in embryo or adult • human embryos develop with webs between toes & fingers, but they are not born that way!

33. Birth positive feedback

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