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Animal Reproduction

Animal Reproduction. Animal Reproduction. Reproduction is asexual or sexual asexual reproduction offspring genetically identical to parent and siblings saves costs of sexual reproduction resulting population lacks genetic variability. Animal Reproduction. Reproduction is asexual or sexual

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Animal Reproduction

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  1. Animal Reproduction

  2. Animal Reproduction • Reproduction is asexual or sexual • asexual reproduction • offspring genetically identical to parent and siblings • saves costs of sexual reproduction • resulting population lacks genetic variability

  3. Animal Reproduction • Reproduction is asexual or sexual • asexual reproduction • various methods • budding • outgrowth from body of parent • regeneration • regrowth of lost body parts or whole organisms

  4. budding of hydraregeneration of a sea starFigure 43.1

  5. parthenogenesis & viviparyin aphid

  6. Animal Reproduction • Reproduction is asexual or sexual • asexual reproduction • various methods • parthenogenesis • production of offspring from unfertilized eggs • may require mating behavior to stimulate development

  7. parthenogenesis in whiptail lizardsFigure 43.2

  8. Animal Reproduction • Reproduction is asexual or sexual • sexual reproduction • offspring differ genetically from parents • involves significant cost • gametogenesis • mating (getting gametes together) • fertilization (syngamy - gamete fusion)

  9. Animal Reproduction • Reproduction is asexual or sexual • sexual reproduction • offspring differ genetically from parents • involves significant cost • resulting population exhibits genetic variability

  10. Animal Reproduction • Reproduction is asexual or sexual • sexual reproduction - genetic variability • combines genetic contributions from male and female parents • gamete genomes contain recombined chromosomes • crossing over (prophase I) • independent assortment (metaphase I)

  11. Animal Reproduction • Reproduction is asexual or sexual • sexual reproduction • alternates the halving and doubling of genomes • meiosis reduces 2n genome to 1n • fertilization combines two 1n gametes

  12. Animal Reproduction • meiosis is part of gametogenesis • gametogenesis occurs in the primary sex organs - the gonads • motile sperm are produced in testes • non-motile eggs (ova) are produced in ovaries

  13. Early stagesof spermatogenesis and oogenesisFigure 43.3

  14. Animal Reproduction • gametogenesis • germ cells enter the gonads during embryonic development • germ cells divide mitotically to produce spermatogonia or oogonia • spermatogonia and oogonia divide mitotically to produce primary spermatocytes and primary oocytes • meiosis produces spermatids and ootids

  15. Animal Reproduction • spermatogenesis • meiosis I divides a primary spermatocyte • produces two secondary spermatocytes • haploid • connected due to incomplete cytokinesis • meiosis II divides secondary spermatocytes • produces four linked spermatids • spermatids develop into sperm

  16. complete spermatogenesisFigure 43.3

  17. Animal Reproduction • oogenesis • primary oocyte enters prophase I • arrests development at prophase I • remains in prophase I for some time • grows & accumulates nutrients, energy, RNA, ribosomes, organelles

  18. human gametesdiffer in size

  19. Animal Reproduction • oogenesis • primary oocyte resumes meiosis I • asymmetric division produces two cells • secondary oocyte • first polar body • secondary oocyte divides asymmetrically in meiosis II • ootid • second polar body

  20. complete oogenesis, minus pausesFigure 43.3

  21. Animal Reproduction • oogenesis • timing of meiosis and egg development varies • secondary oocyte pauses in development prior to meiosis II • meiosis II may occur after expulsion from the ovary • human ova completes meiosis II after fertilization

  22. Fertilization • sperm/egg recognition • recognition molecules ensure that sperm interact with eggs of the same species • jelly layer activates acrosome • acrosomal enzymes digest jelly layer • acrosomal process bears bindinproteins • plasma membrane bears bindin receptors

  23. sea urchin sperm/egg recognitionFigure 43.4

  24. Fertilization • mammalian sperm/egg recognition • sperm capacitation occurs in female reproductive tract • superficial sperm enzymes digest cumulus • zona pellucida glycoproteins bind sperm head recognition proteins • acrosomal enzymes digest zona pellucida • plasma membrane proteins bind sperm adhesion proteins

  25. mammalian barriers to sperm entryFigure 43.5 (follicle cells) (glycoprotein)

  26. fast block to polyspermy in sea urchin:prevents entry by multiple sperm plasma membrane electrical potential rapid Na+ influx

  27. slow block to polyspermyFigure 43.6 sperm entry Ca2+ release exocytosis fertilization envelope

  28. Fertilization • egg activation • mammals • calcium release from ER • cortical granule fusion • removal of sperm-binding proteins • metabolic activation • increased cytoplasmic pH • increased O2 consumption • increased protein synthesis • nuclear fusion ~12 h after sperm entry

  29. simultaneous hermaphroditic fertilization

  30. Animal Reproduction • sexual identity in animals • many animals are dioecious • other animals are monoecious (hermaphroditic) • simultaneous hermaphrodites • sequential hermaphrodites

  31. fertilization • fusion of sperm and egg • produces zygote • requires sperm & egg to be in close proximity

  32. release of sperm and eggs

  33. mating behavior • external fertilization • release of gametes into aquatic environment • chance meeting of egg & sperm • synchronized release by sessile animals • simultaneous release by motile animals

  34. simultaneous release of sperm & eggs

  35. mating behavior • internal fertilization • protects sperm from desiccation • spermatophores - sperm containers • released to environment • inserted into female genital opening

  36. mating behavior • internal fertilization • protects sperm from desiccation • copulation • direct transfer of sperm • requires accessory sex organs • penis • vagina or cloaca

  37. development • site of development varies • oviparous • egg bearing • external development • viviparous • live bearing • internal development in uterus • ovoviviparous • development in eggs retained within body

  38. human reproductive system • male organs produce & deliver sperm • semen • sperm • produced in testes • stored in epididymis • transported through vas deferens • combined with fluids • ejaculated through urethra during copulation

  39. human reproductive system • male organs produce & deliver sperm • semen • bulbourethral fluid • pH buffer & lubricant • seminal fluid • fructose, prostaglandins, mucus/protein • prostate fluid • modifies uterine environment • clots seminal fluid

  40. male primary and accessory sex organsFigure 43.8

  41. sperm production in seminiferous tubulesFigure 43.9

  42. human reproductive system • sperm development • within the scrotum • within seminiferous tubules • developing sperm are engulfed by Sertoli cells • developing sperm migrate from periphery to lumen of tubule • mature sperm are released into lumen and travel to epididymis • Leydig cells produce testosterone

  43. SpermatogenesisFigure 43.9

  44. human reproductive system • hormonal control of sperm development • gonadotropin-releasing hormone (GnRH) • from hypothalamus, stimulates • luteinizing hormone (LH) • from anterior pituitary, stimulates -testosterone release from Leydig cells

  45. human reproductive system • hormonal control of sperm development • spermatogenesis is controlled by • follicle-stimulating hormone (FSH) & • testosterone • on Sertoli cells

  46. control of male sex hormone productionFigure 43.10 [remember to study this figure and explanatory slides associated with it]

  47. oviduct cilia

  48. human reproductive system • female sex organs • ovary produces eggs • eggs are released into oviduct • oviduct transports egg to uterus • embryo implants in uterine wall • cervix retains uterine contents during pregnancy; dilates during birth • sperm enter, baby departs through vagina

  49. female primary and accessory sex organsFigure 43.11

  50. human reproductive system • female reproductive cycles • ovarian cycle ~28 days • production of a secondary oocyte • surrounded, supplied by follicle cells • growth, maturation, first meiotic division • release from ovary • increased hormone production • follicle cells of corpus luteum • produces estrogen & progesterone

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