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Explore the intricate processes of asexual and sexual reproduction, human reproductive systems, gametogenesis, infertility technology, STDs, and contraception methods. Enhance your knowledge on genetic uniqueness, individual variability, and the significance of reproduction for species survival.
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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 • Genetically identical offspring (clones) • 1 parent • No gamete fusion • Mitosis only • Pro • Ease for nonmotile and isolated individuals, and quick • Con • Changing environments
Asexual Reproduction • Fission • Prokaryotes • Invertebrates • Budding • Hydras • Fragmentation • Some sea stars & sponges • Parthenogenesis • Bees, ants, & Komodo dragons
Sexual Reproduction • Simultaneous hermaphroditism • Cross-fertilization • Sequential hermaphroditism • Many fish • Blue-banded gobies • Separate sexes • External • Internal
Fertilization External Internal
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)
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
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
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
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)
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
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
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
