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Animal Reproduction

Animal Reproduction. Types of Reproduction. Asexual. Sexual. Genetic diversity Advantage : ability to change pop. when env . changes Fusion of haploid gametes Egg (Ovum) + Sperm  Zygote. Clone Advantage : FAST, if env . is stable

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Animal Reproduction

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  1. Animal Reproduction

  2. Types of Reproduction Asexual Sexual Genetic diversity Advantage: ability to change pop. when env. changes Fusion of haploid gametes Egg (Ovum) + Sperm  Zygote • Clone Advantage: FAST, if env. is stable • Fission: parent separates into 2+ individuals of same size • Budding: outgrowths from parent (eg. cnidarians, tunicates) • Fragmentation: breaking of body into pieces, form into adults by regeneration (eg. sea stars, sponges, cnidarians) • Parthenogenesis: female produces eggs that develop w/o fertilization (eg. male bees – haploid)

  3. Fission - Sea Anemone Sexual Reproduction – Frogs (External fertilization)

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

  5. 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

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

  7. Reproductive Cycles and Patterns • Ovulation: release of mature eggs • Young produced when survival is most likely • Hormonal changes influenced by day length, season temp, rainfall or lunar cycles • Hermaphroditism: both M/F systems • Sessile/burrowing animals - barnacles, parasites (tapeworms), earthworms • Sex reversal: sex change during its lifetime • Bluehead wrasse (reef fish)

  8. Sex reversal in a sequential hermaphrodite. Wrasses (reef fish) born female, but oldest, largest individuals complete their lives as males. Parthenogenesis in female Blacktip Shark: egg fuses with a polar body

  9. Fertilization = sperm + egg External Fertilization Internal Fertilization Sperm deposited in female reprod. tract Cooperative behavior Dry environment Fewer gametes, fewer zygotes  greater survival • Egg shed by female, fert. by male in water • Environmental cues / courtship behavior • Large # gametes  low survival • Eg. fish, amphibians • External Devel. • Tough eggshell • Eg. reptiles, birds, platypus • Internal Devel. • High parental care • Eg. placentals, sharks, some reptiles

  10. Human Reproductive System

  11. Female Anatomy • Ovaries – produce eggs, sex hormones • Follicles – contain oocyte (egg); release 1/month; produce estrogens • Ovulation – release of egg from follicle • Remaining follicle  corpus luteum (↑hormones) • egg  oviduct (fallopian tube)  uterus (baby)  cervix  vagina • Mammary glands – secrete milk through nipples in breast

  12. Female Reproductive System

  13. Male Anatomy • Testes (inside scrotum) – produce sperm, sex hormones • Seminiferous tubules – make sperm • seminiferous tubules  epididymis  vas deferens  urethra (penis) • semen = alkaline fluid w/nutrients, enzymes • 100-650 million sperm/ejaculation

  14. Male Reproductive System

  15. Meiosis Spermatogenesis Oogenesis Ova production Before birth: oogonia meiosis - STOP at Prophase I (primary oocytes) Puberty: each month, egg in follicle  Meiosis I (secondary oocytes)  fertilization  Meiosis II 1 ovum + 3 polar bodies • Sperm production • Stem cells  spermatids in seminiferous tubules • Mature & add tail in epidymis • 4 motile sperm

  16. 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

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

  18. 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

  19. 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

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

  21. Fertilization

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

  23. 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

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

  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 blastula blastocoel blastomere

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

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

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

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

  31. 1980s | 1995 Hox Genes • Eric Wieschaus • for his discoveries concerning the genetic control of early embryonic development Eric Wieschaus

  32. Human Fetal Development 4 weeks 7 weeks

  33. 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

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

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

  36. 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

  37. 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

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

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

  40. Hormone induction Birth positive feedback

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

  42. The end of the journey! Any Questions!

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