After studying this chapter you will be able to: Distinguish between asexual and sexual reproduction; explain how hermaphroditism may be advantageous to animals that have difficulty encountering a member of the opposite sex; describe various ways in which animals may protect developing embryos; using diagrams, identify and state the function of each component of the male and female reproductive systems.
Ch 46 Warm-Up What is the advantage of sex vs asex(ual) reproduction? List at least different modes of asexual reproduction What are the types of human gametes? Where is each produced? Define and give an example of parthenogenesis Chapter 46 Animal Reproduction Types of Reproduction Asexual • Clone Advantage: FAST, if env is stable Fission: parent separates into 2+ individuals of same size Budding: outgrowths from parent (eg cnidarians, tunicates) Fragmentation: breaking of body into pieces, form into adults by regeneration (eg sea stars, sponges, cnidarians) Parthenogenesis: female produces eggs that develop w/o fertilization (eg male bees – haploid) Sexual • Genetic diversity Advantage: ability to change pop when env changes • Fusion of haploid gametes Egg (Ovum) + Sperm Zygote Fission - Sea Anemone Sexual Reproduction – Frogs (External fertilization) Reproductive Cycles and Patterns Ovulation: release of mature eggs – Young produced when survival is most likely – Hormonal changes influenced by day length, season temp, rainfall or lunar cycles Hermaphroditism: both M/F systems – Sessile/burrowing animals - barnacles, parasites (tapeworms), earthworms Sex reversal: sex change during its lifetime – Bluehead wrasse (reef fish) Sex reversal in a sequential hermaphrodite Wrasses (reef fish) born female, but oldest, largest individuals complete their lives as males Parthenogenesis in female Blacktip Shark: egg fuses with a polar body Fertilization = sperm + egg External Fertilization • Egg shed by female, fert by male in water • Environmental cues / courtship behavior • Large # gametes low survival • Eg fish, amphibians Internal Fertilization • Sperm deposited in female reprod tract • Cooperative behavior • Dry environment • Fewer gametes, fewer zygotes greater survival External Devel •Tough eggshell •Eg reptiles, birds, platypus Internal Devel •High parental care •Eg placentals, sharks, some reptiles Human Reproductive System MALE FEMALE produce eggs development of baby Function Produce & deliver sperm Main reproductive organs Testes (singular: testis) Ovaries Reproductive cells (Gametes) Spermatogenesis SPERM Oogenesis EGGS Main hormone Testosterone Estrogens Role of FSH (folliclestimulating hormone) Sperm formation Egg development (in follicle) Role of LH (luteinizing hormone) Produce testosterone Release of egg (ovulation) Female Anatomy • Ovaries – produce eggs, sex hormones • Follicles – contain oocyte (egg); release 1/month; produce estrogens • Ovulation – release of egg from follicle – Remaining follicle corpus luteum (↑hormones) • egg oviduct (fallopian tube) uterus (baby) cervix vagina • Mammary glands – secrete milk through nipples in breast Female Reproductive System Menstrual cycle – humans & other primates • Prepare and release egg for fertilization • Prepare uterus to receive a fertilized egg Estrous cycle – other mammals; no menstruation Four Phases of Menstrual Cycle: Follicular Phase : low estrogen, ↑FSH = egg develops in ovary Ovulation (Day 14): ↑LH = egg released into Fallopian tube Luteal Phase : • ↑progesterone, ↑estrogen = lining of uterus thickens to prepare for pregnancy • Egg travels down Fallopian tube, waits for fertilization Menstruation (no fertilization) : • ↓P/↓E = lining of uterus breaks down • Blood and unfertilized egg discharged Human female reproductive cycle Human embryonic development • Conception: in oviduct • Implantation: in uterus • Hormones: – Human Chorionic Gonadotropin (hCG): maintain estrogens in early pregnancy; pregnancy test • Human gestation (pregnancy) = 40 weeks – Rodents (21 days); Dogs (60 days); Cows (270 days); Elephants (600 days) • Egg lodged in oviduct = ectopic (tubal) pregnancy Formation of Zygote Cleavage starts Cleavage continues Ovary Fertilization occurs The blastocyst implants Ovulation Uterus Endometrium From ovulation to implantation Early Postfertilization Events Endometrium Inner cell mass Cavity Blastocyst Implantation of blastocyst Trophoblast Placental Circulation Human Fetal Development The Three Stages of Labor How does “the Pill” work? • • • • • “the Pill” is an oral contraceptive Contains estrogen and progesterone First available in 1960 Main effect: Prevent ovulation Other effects: – Thickens cervical mucus – slows down sperm – Thins uterus lining – prevent implantation of fertilized egg • Usage: active pill for 21 days, inactive pills for days (“period”) • Other medical uses: – – – – – Medication for mild/moderate acne Decrease painful menstruation Treat polycystic ovary syndrome (PCOS) Correct irregular menstrual cycle Reduce risk of ovarian and endometrial cancers Mechanisms of some contraceptive methods .. .Chapter 46 Animal Reproduction Types of Reproduction Asexual • Clone Advantage: FAST, if env is stable Fission: parent... male bees – haploid) Sexual • Genetic diversity Advantage: ability to change pop when env changes • Fusion of haploid gametes Egg (Ovum) + Sperm Zygote Fission - Sea Anemone Sexual Reproduction. .. day length, season temp, rainfall or lunar cycles Hermaphroditism: both M/F systems – Sessile/burrowing animals - barnacles, parasites (tapeworms), earthworms Sex reversal: sex change during