ANIMAL REPRODUCTION

1. ANIMAL REPRODUCTION Ch. 12.6 – 12.10 Bio 391

2. Animals • Reproduce sexually • Gonads • Produce gametes • Ovaries  ovum • Testes  sperm • Many simple animals (hydra, sponges) make both eggs & sperm but do NOT self-fertilize

3. Fertilization • External Fertilization • Simple, aquatic animals • Gametes released into water • No guarantee of fertilization • No protection for zygote • Internal Fertilization • Male ejaculates sperm into female • Fertilization inside female body • Gametes protected • Increased likelihood of fertilization • Requires fewer gametes • Zygote protected inside female

4. Although internal fertilization uses less eggs, still lots of sperm required • Ensures fertilization • Sperm don’t live long • Must swim long distance & few make it • Enzymes within sperm head required to weaken egg’s membrane allowing one sperm to penetrate

5. Mating Rituals • For fertilization to occur, sperm & egg must be released at about the same time • Mating rituals can… • Signal the right time for fertilization • Bring the gametes into close proximity • Frogs: • Male sits on female, and grabs on • Triggers female to release eggs into water • Male follows with sperm release over eggs

6. Egg vs. Sperm • Egg • Large • Immobile • Nutrient storehouse • Can survive longer • Sperm • Mobile • Smaller • Nucleus, flagella, mitochondria • No stored food  cannot survive long

7. Mammalian Reproduction • Have hair and produce milk • Internal Fertilization • Developmental location varies

8. 3 Groups of Mammals

9. Female Anatomy

10. ~ 28 days Endometrium Uterine lining Thickens with blood vessels in prep for fertilized egg If no egg, disintegrates and released “menstrual flow” Controlled by nervous system, glands, organs, hormones Hypothalamus controls hormone levels, like a thermostat Menstrual Cycle

11. Hormones and the Endocrine System • GnRH, estrogen, progesterone, FSH, LH, oxytocin; testosterone • http://www.youtube.com/watch?v=G1LuM0kKtpY&NR=1 • http://www.youtube.com/watch?v=tK4lzxQuxTM&feature=related

12. Low estrogen & progesterone cause hypothalamus to secrete GnRH Stimulates pituitary to release FSH  causes egg to mature in ovary LH  causes follicle to burst @ 14 days FSH & LH stimulate maturing follicle to increase estrogen release Menstrual Cyclehttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/animation__positive_and_negative_feedback__quiz_1_.html

13. Estrogen triggers uterine lining to thicken 14 days – LH triggers ovulation Ruptured follicle now = corpus luteum Continues to release more estrogen & progesterone  continues to thicken uterine lining Hypothalamus slows down FSH & LH release Menstrual Cycle

14. If egg NOT fertilized… Corpus luteum disintegrates Decrease in estrogen & progesterone Uterine lining breaks down Menstrual flow Menstrual Cycle

15. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__maturation_of_the_follicle_and_oocyte.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__maturation_of_the_follicle_and_oocyte.html

16. Oogenesis (meiosis I) begin at birth & proceed in discontinuous stages The second meiotic division occurs only after fertilization by sperm; gametogenesis in the female is dependent on fertilization for completion.

17. If egg IS fertilized… • Mitosis forms an embryo • Implantation • Placenta forms • Placenta releases HCG (human chorionic gonadotropin) • Signals corpus luteum to continue releasing high levels of estrogen & progesterone for uterine lining support • Corpus luteum lasts 3 months • Then placenta = source of estrogen & progesterone

20. Development & Birth • Gestation • Development of embryo in uterus • “pregnancy” • Birth • Oxytocin released  causes uterus to contract • Also stimulates milk production & release • Stimulates placenta to release prostaglandins that further trigger contractions • Baby born • Placenta released

22. A side note… • Menstruation  female primates • Estrus  most other mammals • “in heat” • Number of times per year and the timing of the cycles vary by organism

23. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__spermatogenesis__quiz_1_.htmlhttp://www.youtube.com/watch?v=WEzcK-OKd10&feature=relatedhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__spermatogenesis__quiz_1_.htmlhttp://www.youtube.com/watch?v=WEzcK-OKd10&feature=related

24. Male Reproductive System • Ejaculation • What is it and why? • What happens to sperm that aren’t released? • Male Hormones • Androgens • Testosterone • GnRH from hypothalamus stimulates pituitary to release FSH and LH • LH causes release of androgens • FSH stimulates sperm production

25. Secondary Sex Characteristics • Estrogen & Androgen • Begin at puberty  the beginning of sexual maturation • Females – starts with first menstrual period • Approx. ages 10-12 in North America (what about in Africa?) • Males – approx. age 12 in North America • Females • Breasts, fat deposits, bone structure • Males • Voice changes, body hair

26. Infertility & Contraception • Infertility • Males  weak sperm, low count, etc. • Females  blocked oviducts, irregular cycle, etc. • In-vitro fertilization, fertility drugs • Contraception • Physical barriers  condoms, diaphragms, cervical cap • Chemical  prevent ovulation or implantation • Hormone based • “The pill”, injections, Norplant • Foams/Jellies/Sponges – in vagina before sex to immobilize or kill sperm • Surgery • Abstinence