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Chapter 36 – Animal Reproduction

Chapter 36 – Animal Reproduction. Why study animal reproduction? How do animals reproduce? Why do genders develop? What causes sexual maturity? What causes animals to reproduce? Is sexual attraction biological? How does fertilization occur? How does contraception prevent fertilization?

germane-atkinson
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Chapter 36 – Animal Reproduction

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  1. Chapter 36 – Animal Reproduction • Why study animal reproduction? • How do animals reproduce? • Why do genders develop? • What causes sexual maturity? • What causes animals to reproduce? • Is sexual attraction biological? • How does fertilization occur? • How does contraception prevent fertilization? • What diseases result from promiscuous sexual activity?

  2. Why study animal reproduction?

  3. Why study animal reproduction?

  4. Why study animal reproduction?

  5. Why study animal reproduction?

  6. Why study animal reproduction?

  7. Why study animal reproduction?

  8. Why study animal reproduction?

  9. Why study animal reproduction?

  10. Why study animal reproduction?

  11. How do animals reproduce? • Asexual reproduction • Sexual reproduction

  12. How do animals reproduce? • Asexual reproduction • Fission • Budding • Parthenogenesis

  13. Chalk bass Marine flatworm How do animals reproduce? • Sexual reproduction • Dioecious species • Monoecious species • Hermaphrodites

  14. Red grouper How do animals reproduce? • Sexual reproduction • Sex changers – 77 known animal species (fish, crustaceans, mollusks) change gender (at ~72% of maximum size, change from female to male)

  15. Animal reproductive strategies • External fertilization, external development

  16. Animal reproductive strategies • Internal fertilization, external development

  17. Internal fertilization, external development = egg layers

  18. Internal fertilization requires copulation

  19. Copulation • -Flatworms • -Landsnails • -Rattlebox moth • -BJU link Copulation in Pisaura mirabilis. The female consumes the nuptial gift while the male transfer sperm with his pedipalps. Foto: Allan Lau

  20. Internal fertilization, internal development

  21. Why are there genders?

  22. Why are their genders? • SRY gene and male development • -Located on Y chromosome • -Codes for an enzyme, Testis Determining Factor • Testis produce hormones • -MIF – Mullerian Inhibiting Factor • -Androgens (bind to androgen receptor)

  23. Androgens and male development • Testosterone – internal male organ development 5α-reductase Testosterone Dihydrotestosterone DHT – development of penis and scrotum

  24. What would happen if there was a genetic mutation… • …in SRY gene? • …in the androgen receptor gene? • …in the 5α-reductase gene?

  25. Androgen insensitivity syndrome • -Genetic (XY) male, external female genitalia • -Usually raised as a female, sterile • -Male characteristics • -Olympic female athletes tested

  26. 5-Alpha reductase deficiency syndrome • -change from female to male at puberty • -Born with external female appearance, but internal male sex organs • -At puberty, androgens result in completion of male development • -1 in 4500 have ambiguous gender

  27. Ambiguous gender and Christianity • How should a person with ambiguous gender handle their sexuality? • Since ambiguous gender is natural, can the type of attraction experienced be regarded as sinful?

  28. What causes sexual maturity? • Puberty

  29. mitosis more spermatogonia

  30. Oogenesis

  31. Ovulation

  32. What causes animals to reproduce? • Sexual attraction • Is there a biological basis to sexual attraction? • What determines who you are sexually attracted to?

  33. What causes animals to reproduce? • Chemical attraction - pheromones

  34. What causes animals to reproduce? • VNO – vomeronasal organ

  35. Is sexual attraction biological? • Pheromones & pheromone receptors (VNO) • Androgens & brain development

  36. Is sexual attraction biological? • Androgens influences brain development

  37. Is sexual attraction biological?

  38. Is sexual attraction biological?

  39. Do brain differences influence sexual behavior or vice versa? • Breedlove, M., Sex on the Brain, Nature, Oct. 23, 1997, p. 801

  40. Is sexual attraction biological? • Adrenogenital syndrome • Adrenal glands secrete abnormally high levels of androgens (prenatal) • -External genitalia may be intermediate • Study of 30 affected adult women • -48% were homo- or bi-sexual

  41. Is sexual attraction biological? • Animals’ Fancies • Roy & Silo • Fruitless mutations • Comparison of auditory systems

  42. Current scientific understanding of sexuality

  43. Variations of sexual attraction

  44. Sexuality involves genetics & environment • Source: The Complex Interaction of Genes and Environment: A Model for Homosexuality (Satinover, J., 1995)

  45. How does fertilization occur?

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