Chapter 36 animal reproduction
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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?

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Chapter 36 – Animal Reproduction

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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?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


Why study animal reproduction?


How do animals reproduce?

  • Asexual reproduction

  • Sexual reproduction


How do animals reproduce?

  • Asexual reproduction

    • Fission

    • Budding

    • Parthenogenesis


Chalk bass

Marine flatworm

How do animals reproduce?

  • Sexual reproduction

    • Dioecious species

    • Monoecious species

      • Hermaphrodites


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)


Animal reproductive strategies

  • External fertilization, external development


Animal reproductive strategies

  • Internal fertilization, external development


Internal fertilization, external development = egg layers


Internal fertilization requires copulation


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


Internal fertilization, internal development


Why are there genders?


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)


Androgens and male development

  • Testosterone – internal male organ development

5α-reductase

Testosterone

Dihydrotestosterone

DHT – development of penis and scrotum


What would happen if there was a genetic mutation…

  • …in SRY gene?

  • …in the androgen receptor gene?

  • …in the 5α-reductase gene?


Androgen insensitivity syndrome

  • -Genetic (XY) male, external female genitalia

  • -Usually raised as a female, sterile

  • -Male characteristics

  • -Olympic female athletes tested


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


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?


What causes sexual maturity?

  • Puberty


mitosis

more spermatogonia


Oogenesis


Ovulation


What causes animals to reproduce?

  • Sexual attraction

  • Is there a biological basis to sexual attraction?

  • What determines who you are sexually attracted to?


What causes animals to reproduce?

  • Chemical attraction - pheromones


What causes animals to reproduce?

  • VNO – vomeronasal organ


Is sexual attraction biological?

  • Pheromones & pheromone receptors (VNO)

  • Androgens & brain development


Is sexual attraction biological?

  • Androgens influences brain development


Is sexual attraction biological?


Is sexual attraction biological?


Do brain differences influence sexual behavior or vice versa?

  • Breedlove, M., Sex on the Brain, Nature, Oct. 23, 1997, p. 801


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


Is sexual attraction biological?

  • Animals’ Fancies

  • Roy & Silo

  • Fruitless mutations

  • Comparison of auditory systems


Current scientific understanding of sexuality


Variations of sexual attraction


Sexuality involves genetics & environment

  • Source: The Complex Interaction of Genes and Environment: A Model for Homosexuality (Satinover, J., 1995)


How does fertilization occur?


Fertilization


Fertilization


How does sperm recognize the egg?


Integrins

ADAMS

How does sperm recognize the egg?


Human copulation

  • Sperm delivery requires an orgasm

  • 300-500 million sperm released, only a few hundred reach the egg

  • Pig orgasm lasts ~30 minutes


How does contraception prevent fertilization?


What diseases result from promiscuous sexual activity?

  • Sexually Transmitted Diseases (STDs) – U.S.

  • 1 in 5 adults infected

  • 45 million have chronic genital herpes (1 million new cases/yr.)

  • 20 million cases of HPV – genital warts, cervical cancer (5.5 million new cases/yr.)

  • 5 million cases trichomoniasis/yr.

  • 3 million new cases of chlamydia each year

  • 650,000 new gonorrhea cases/yr.


Pelvic Inflamatory Disease

Infertility & STDs


Infertility – 1 in 6 couples unable to conceive naturally

  • Sexually transmitted diseases

  • Low sperm count (substance abuse, alcohol, tobacco, marijuana)

  • Mutations in egg/sperm membrane proteins


Infertility and genetic mutation


What diseases result from promiscuous sexual activity?

  • Source: World Health Organization


U.S. AIDS cases through 2001 (CDC)

  • Total possible AIDS cases caused by heterosexual contact with non-IV drug using heterosexual: 54, 773 (<7%)


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