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Reproduction

Reproduction. Chapter 27. Reproduction. Asexual. Sexual. Genetically unique individuals 2 parents Haploid gametes (n) fuse (2n) Egg: large, nonmotile , female Sperm: small, motile, male Mitosis and meiosis Pro Variability = better survival chance Con Finding mates.

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Reproduction

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  1. Reproduction Chapter 27

  2. Reproduction Asexual Sexual Genetically unique individuals 2 parents Haploid gametes (n) fuse (2n) Egg: large, nonmotile, female Sperm: small, motile, male Mitosis and meiosis Pro Variability = better survival chance Con Finding mates • Genetically identical offspring (clones) • 1 parent • No gamete fusion • Mitosis only • Pro • Ease for nonmotile and isolated individuals, and quick • Con • Changing environments

  3. Asexual Reproduction • Fission • Prokaryotes • Invertebrates • Budding • Hydras • Fragmentation • Some sea stars & sponges • Parthenogenesis • Bees, ants, & Komodo dragons

  4. Sexual Reproduction • Simultaneous hermaphroditism • Cross-fertilization • Sequential hermaphroditism • Many fish • Blue-banded gobies • Separate sexes • External • Internal

  5. Fertilization External Internal

  6. Human Reproductive Systems

  7. Female Reproductive System • Ovaries and follicles produce estrogen • Follicles release eggs about every 28 days • Without fertilization, corpus luteum and endometrium degenerate • Occurs in oviduct • Zygote, embryo, fetus (9th week)

  8. Male Reproductive System • Sperm • Develop in seminiferous tubules • Epididymis store while developing • Semen • Seminal vesicles: nutrients for energy and uterine entry • Prostate gland: nourishes and activates • Bulbourethral glands: neutralize urethra • Ejaculation • Bladder sphincter contracts • Ducts and glands contract to propel semen • Urethra sphincter relaxes • Contractions of penis releases semen

  9. Oogenesis • Prior to birth • Cell in follicle undergo mitosis and start meiosis • Birth • Primary oocyte(2n) halted at prophase I • Puberty • LH stimulates meiosis I completion • Secondary oocyte(n) halted at metaphase II & polar body • Ovulation releases • Fertilization completes meiosis • Second polar body

  10. Spermatogenesis • Diploid cells undergo mitosis after puberty • 1 Primary (2n) to 2 secondaryspermatocytes (n) • Secondary spermatocyte to 2 spermatids • Completes meiosis to become sperm • Process about 10 weeks

  11. Gametogenesis Oogenesis Spermatogenesis Mitotic division adolescence till death 4 spermatocytes result Mature sperm continuously produced • Mitotic division completed by birth • 1 oocyte develops, polar bodies degenerate • 1 ovum per cycle (28 days)

  12. Fertilization

  13. Infertility Technology Male Female Lack of eggs Implant from a donor Risk to donor Failure to ovulate Hormone injections Multiple pregnancies Can’t support embryo Surrogate mother In vitro fertilization • Sperm count low or defective • Scrotum temperature change • Sperm bank • Impotence • Viagra • Implants (irreversible) • Intracytoplasmic sperm injection

  14. STD’s • United States w/ highest rates (developed countries) • Bacterial and fungal • Antibiotics can cure if early; resistance • Gonorrhea, chlamydia, and syphilis • Candidiasis • Viral • Not curable, but controllable; infect others for life • Genital herpes (most difficult), HPV, HIV • Protozoan • Trichomoniasis

  15. Contraception • Sterilization prevents gamete transport • Condoms prevent pregnancy and STD’s • Abstinence only 100% • Rhythm method is unreliable • 3-5 day sperm survival rate • Oral contraceptives prohibit hormonal signal to follicle • Morning after pill • RU486 induces abortion (7 weeks) • Blocks progesterone receptors

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