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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;...
Chapter 46 Animal Reproduction PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece LecturesbyChrisRomero Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Overview: Doubling Up for Sexual Reproduction The two earthworms in this picture are mating • Each worm produces both sperm and eggs, which will fertilize – And in a few weeks, new worms will hatch Figure 46.1 Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings A population transcends finite life spans Only by reproduction Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Concept 46.1: Both asexual and sexual reproduction occur in the animal kingdom • Asexual reproduction is the creation of new individuals – Whose genes all come from one parent Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Sexual reproduction is the creation of offspring – By the fusion of male and female gametes to form a zygote • The female gamete is the egg • The male gamete is the sperm Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings MechanismsofAsexualReproduction Many invertebrates reproduce asexually by fission The separation of a parent into two or more individuals of approximately the same size Figure 46.2 Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Also common in invertebrates is budding – In which two new individuals arise from outgrowths of existing ones • Another type of asexual reproduction is fragmentation, which – Is the breaking of the body into several pieces, some or all of which develop into complete adults – Must be accompanied by regeneration, the regrowth of lost body parts Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings ReproductiveCyclesandPatterns Most animals exhibit cycles in reproductive activity – Often related to changing seasons • Reproductive cycles – Are controlled by hormones and environmental cues Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Animals may reproduce exclusively asexually or sexually – Or they may alternate between the two • Some animals reproduce by parthenogenesis – A process in which an egg develops without being fertilized Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Among vertebrates, several genera of fishes, amphibians, and lizards, including whiptail lizards – Reproduce exclusively by a complex form of parthenogenesis Hormones Ovary size (a) Both lizards in this photograph are C uniparens females The one on top is playing the role of a male Every two or three weeks during the breeding season, individuals switch sex roles Estrogen Ovulation Ovulation Progesterone Behavior Time Figure 46.3a, b Female- Malelike like Female- Malelike like Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) The sexual behavior of C uniparens is correlated with the cycle of ovulation mediated by sex hormones As blood levels of estrogen rise, the ovaries grow, and the lizard behaves like a female After ovulation, the estrogen level drops abruptly, and the progesterone level rises; these hormone levels correlate with male behavior • Blood from the embryo – Travels to the placenta through arteries of the umbilical cord and returns via the umbilical vein Maternal arteries Maternal veins Placenta Maternal portion of placenta Umbilical cord Chorionic villus containing fetal capillaries Fetal portion of placenta (chorion) Maternal blood pools Uterus Figure 46.16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fetal arteriole Fetal venule Umbilical cord Umbilical arteries Umbilical vein • The first trimester is the main period of organogenesis – The development of the body organs (a) weeks Limb buds, eyes, the heart, the liver, and rudiments of all other organs have started to develop in the embryo, which is only about cm long Figure 46.17a–c (b) 14 weeks Growth and development of the offspring, now called a fetus, continue during the second trimester This fetus is about cm long Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (c) 20 weeks By the end of the second trimester (at 24 weeks), the fetus grows to about 30 cm in length Second Trimester • During the second trimester – The fetus grows and is very active – The mother may feel fetal movements – The uterus grows enough for the pregnancy to become obvious Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Third Trimester • During the third trimester – The fetus continues to grow and fills the available space within the embryonic membranes Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings A complex interplay of local regulators and hormones – Induces and regulates labor, the process by which childbirth occurs Oxytocin from ovaries from fetus and mother's posterior pituitary Induces oxytocin receptors on uterus Stimulates uterus to contract Stimulates placenta to make Prostaglandins Figure 46.18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stimulate more contractions of uterus Positive feedback Estrogen • Birth, or parturition – Is brought about by a series of strong, rhythmic uterine contractions Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings The process of labor has three stages Placenta Umbilical cord Uterus Cervix Dilation of the cervix Expulsion: delivery of the infant Uterus Placenta (detaching) Umbilical cord Figure 46.19 Delivery of the placenta Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Mother’s Immune Tolerance of the Embryo and Fetus • A woman’s acceptance of her “foreign” offspring – Is not fully understood – May be due to the suppression of the immune response in her uterus Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings ContraceptionandAbortion Contraception, the deliberate prevention of pregnancy – Can be achieved in a number of ways Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Some contraceptive methods – Prevent the release of mature eggs and sperm from gonads – Prevent fertilization by keeping sperm and egg apart Prevent implantation of an embryo Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Mechanisms of some contraceptive methods Female Male Method Event Event Production of viable sperm Method Production of viable oocytes Vasectomy Ovulation Sperm transport down male duct system Abstinence Combination birth control pill (or injection, patch, or vaginal ring) Abstinence Condom Coitus interruptus (very high failure rate) Sperm deposited in vagina Capture of the oocyte by the oviduct Tubal ligation Sperm movement through female reproductive tract Transport of oocyte in oviduct Spermicides; diaphragm; cervical cap; progestin alone (minipill, implant, or injection) Meeting of sperm and oocyte in oviduct Union of sperm and egg Morning-after pill (MAP) Progestin alone Implantation of blastocyst in properly prepared endometrium Figure 46.20 Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Birth ModernReproductiveTechnology Recent scientific and technological advances – Have made it possible to deal with many reproductive problems Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Amniocentesis and chorionic villus sampling – Are invasive techniques in which amniotic fluid or fetal cells are obtained for genetic analysis Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Noninvasive procedures – Usually use ultrasound imaging to detect fetal condition Head Head Body Figure 46.21 Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Body Modern technology – Can help infertile couples by in vitro fertilization Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ... spans – Only by reproduction Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Concept 46.1: Both asexual and sexual reproduction occur in the animal kingdom • Asexual reproduction. .. Copyrightâ2005PearsonEducation,Inc.publishingasBenjaminCummings Animals may reproduce exclusively asexually or sexually – Or they may alternate between the two • Some animals reproduce by parthenogenesis – A process... roles Estrogen Ovulation Ovulation Progesterone Behavior Time Figure 46.3a, b Female- Malelike like Female- Malelike like Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings