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Chapter 42-43

Animal Reproduction. Chapter 42-43. Sexual vs. Asexual R eproduction. Asexual offspring all have same genes no variation Sexual gametes (sperm & egg)  fertilization mixing of genes  variation. Fertilization. Joining of egg & sperm external usually aquatic animals internal

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Chapter 42-43

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  1. Animal Reproduction Chapter 42-43

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

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

  4. 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

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

  6. 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

  7. Hypothalamus GnRH Pituitary FSH & LH Testes testosterone Body cells Sex Hormone Control in Males

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

  9. Endocrine System Control 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 pituitarygland hCG pregnancy progesterone GnRH corpus luteum breaks down progesterone drops menstruation maintainsuterus lining hypothalamus

  10. Egg Maturation in Ovary • Corpus luteum • produces progesterone to maintain uterine lining

  11. Fertilization

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

  13. Fertilization causes changes… • yolk found at vegetal hemisphere • embryo at animal hemisphere (pigmented) • post fertilization, animal pole rotates to where sperm penetrates the egg—forming the gray cresent

  14. …which sets up signal cascades to help set up the body plan.

  15. 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

  16. Cleavage • zygote  morula blastula • establishes future development blastula blastocoel blastomere

  17. Blood Cell Production • Stem cells • pluripotent cells • in bone marrow • produce all types of blood cells • cells differentiate in bone marrow & lymph tissue

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

  19. HoxGenes • found in animals to determine body plan! Chapter 19!

  20. HoxGenes • genes that control differentiation on anterior-posterior axis • hedgehog v. sonic hedgehog

  21. 1980s | 1995 Hox Genes • Eric Wieschaus • for his discoveries concerning the genetic control of early embryonic development Eric Wieschaus

  22. Human Fetal Development 4 weeks 7 weeks

  23. 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

  24. Human Fetal Development 10 weeks chorionic villus sampling—as early as week 8

  25. Human Fetal Development amniocentesis: weeks 14-18 12 weeks 20 weeks

  26. 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

  27. 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

  28. Human Fetal Development • 30 weeks (7.5 months)

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

  30. Hormone induction Birth positive feedback

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

  32. The end of the journey! Any Questions!

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