3Sexual & asexual reproduction offspring all have same genes (clones)no variationSexualgametes (sperm & egg) fertilizationmixing of genes variation
4Parthenogenesis Development of an unfertilized egg honey bees drones = males produced through parthenogenesis haploidworkers & queens = females produced from fertilized eggs diploidHoney bee eggs hatch regardless of whether the are fertilized. The female bees--queens & workers--develop from fertilized eggs that contain 32 chromosomes. These 32 chromosomes consist of two sets of 16, one set from each parent. Hence female bees are said to be diploid in origin. The males (drones) develop from unfertilized egg which contain only one set of 16 chromosomes from their mother. Drones are thus haploid in origin This reproduction by the development of unfertilized eggs is called parthenogenesisDrones develop by parthenogenesis from unfertilized eggs that the queen produces by withholding sperm from the eggs laid in large drone cells. Drones lack stings and the structures needed for pollen collection; in the autumn they are ejected by the colony to starve, unless the colony is queenless. New drones are produced in the spring for mating.Both queens and workers are produced from fertilized eggs. Queen larvae are reared in special peanut-shaped cells and fed more of the pharyngeal gland secretions of the nurse bees (bee milk or royal jelly) than the worker larvae are. The precise mechanism for this caste differentiation is still uncertain. Although workers are similar in appearance and behavior to other female bees, they lack the structures for mating. When no queen is present to inhibit the development of their ovaries, however, workers eventually begin to lay eggs that develop into drones.queenworkerdrone
5Honey bee eggs hatch regardless of whether the are fertilized Honey bee eggs hatch regardless of whether the are fertilized. The female bees--queens & workers--develop from fertilized eggs that contain 32 chromosomes. These 32 chromosomes consist of two sets of 16, one set from each parent. Hence female bees are said to be diploid in origin. The males (drones) develop from unfertilized egg which contain only one set of 16 chromosomes from their mother. Drones are thus haploid in origin This reproduction by the development of unfertilized eggs is called parthenogenesisDrones develop by parthenogenesis from unfertilized eggs that the queen produces by withholding sperm from the eggs laid in large drone cells. Drones lack stings and the structures needed for pollen collection; in the autumn they are ejected by the colony to starve, unless the colony is queenless. New drones are produced in the spring for mating.Both queens and workers are produced from fertilized eggs. Queen larvae are reared in special peanut-shaped cells and fed more of the pharyngeal gland secretions of the nurse bees (bee milk or royal jelly) than the worker larvae are. The precise mechanism for this caste differentiation is still uncertain. Although workers are similar in appearance and behavior to other female bees, they lack the structures for mating. When no queen is present to inhibit the development of their ovaries, however, workers eventually begin to lay eggs that develop into drones.
6Different strokes… gay penguins parthenogenesis in aphids “lesbian” lizardssex-change in fish
7Hermaphrodites earthworms mating flat worm Having functional reproductive system of both sexesearthworms matingflat worm
8Fertilization Joining of egg & sperm external internal usually aquatic animalsinternalusually land animals
9Development External Internal development in eggs fish & amphibians in watersoft eggs= exchange across membranebirds & reptiles on landhard-shell amniotic eggsstructures for exchange of food, O2 & wastesharks & some snakeslive births from eggsInternalplacentaexchange food & wastelive birth
10Adaptive advantages?What is the adaptive value of each type of sexual reproductionnumber of eggs?level of parental of carehabitat?
11Reproductive hormones Testosteronefrom testesfunctionssperm production2° sexual characteristicsEstrogenfrom ovariesegg productionprepare uterus for fertilized eggLH & FSHtestes or ovaries
12Male reproductive system Sperm productionover 100 million produced per day!~2.5 million released per drop!
13Spermatogenesis MEIOSIS I MEIOSIS II Epididymis Testis Germ cell (diploid)Coiledseminiferoustubules1°spermatocyte(diploid)MEIOSIS I2°spermatocytes(haploid)MEIOSIS IIVas deferensSpermatids(haploid)SpermatozoaCross-section ofseminiferous tubule
16Menstrual cycle Hypothalamus Pituitary Ovaries Body cells GnRH LHFSHHypothalamusegg developmentovulation = egg releaseGnRHcorpus luteumPituitaryFSH & LHestrogenprogesteroneOvarieslining of uterusestrogenBody cellsdays7142128
17Egg maturation in ovary Corpus luteumproduces progesterone to maintain uterine lining
18Female hormones FSH & LH release from pituitary stimulates egg development & hormone releasepeak release = release of egg (ovulation)Estrogenreleased from ovary cells around developing eggstimulates growth of lining of uteruslowered levels = menstruationProgesteronereleased from “corpus luteum” in ovariescells that used to take care of developing eggstimulates blood supply to lining of uterus
19Oogenesis Unequal meiotic divisions unequal distribution of cytoplasm What is the advantage of this development system?Unequal meiotic divisionsunequal distribution of cytoplasm1 egg2 polar bodiesMeiosis 1 completedduring egg maturationovulationMeiosis 2 completedtriggered by fertilizationPut all your egg in one basket!
21FertilizationJoining of sperm & eggsperm head (nucleus) enters egg
22What is the effect of sperm binding on Ca2+ distribution in the egg? A fluorescent dye that glows when it binds free Ca2+ was injected into unfertilized sea urchin eggs. After sea urchinsperm were added, researchers observed the eggs in a fluorescence microscope.EXPERIMENTRESULTSThe release of Ca2+ from the endoplasmic reticulum into the cytosol at the site of sperm entry triggers the releaseof more and more Ca2+ in a wave that spreads to the other side of the cell. The entire process takes about 30 seconds.CONCLUSION30 sec20 sec10 sec afterfertilization1 sec beforePoint ofSpermentrySpreading waveof calcium ions500 m
23Timeline for the fertilization of sea urchin eggs Binding of sperm to eggAcrosomal reaction: plasma membranedepolarization (fast block to polyspermy)Increased intracellular calcium levelCortical reaction begins (slow block to polyspermy)Formation of fertilization envelope completeIncreased intracellular pHIncreased protein synthesisFusion of egg and sperm nuclei completeOnset of DNA synthesisFirst cell division1234681020304050560SecondsMinutes90
24Cleavage Repeated mitotic divisions of zygote 1st step to becoming multicellularunequal divisions establishes body plandifferent cells receive different portions of egg cytoplasm & therefore different regulatory signals
25Cleavage zygote morula blastula establishes future development gastrulationmorulablastula
26Gastrulation Establish 3 cell layers ectoderm outer body tissues gastrulation in primitive chordatesEstablish 3 cell layersectodermouter body tissuesskin, nails, teeth,nerves, eyes, lining of mouthmesodermmiddle tissuesblood & lymph, bone & notochord, muscle, excretory & reproductive systemsendoderminner liningdigestive system, lining of respiratory, excretory & reproductive systemsectodermmesodermendodermprotostome vs. deuterostome
27Testing…All of the following correctly describe the fate of the embryonic layers of a vertebrate EXCEPTA. neural tube and epidermis develop from ectodermB. linings of digestive organs and lungs develop from endodermC. notochord and kidneys develop from endodermD. skeletal muscles and heart develop from mesodermE. reproductive organs and blood vessels develop from mesoderm
28Testing…In a study of the development of frogs, groups of cells in the germ layers of several embryos in the early gastrula stage were stained with five different dyes that do not harm living tissue. After organogenesis (organ formation), the location of the dyes was noted, as shown in the table below.Tissue StainBrain RedNotochord YellowLiver GreenLens of the eye BlueLining of the digestive tract Purple
29Neurulation Formation of notochord & neural tube develop into nervous systemdevelops into CNS (brain & spinal cord)Neural tubeNotochorddevelops into vertebral column
31Four stages in early embryonic development of a human Endometrium(uterine lining)Inner cell massTrophoblastBlastocoelExpandingregion oftrophoblastEpiblastHypoblastAmnioticcavityChorion (fromtrophoblast)Yolk sac (fromhypoblast)Extraembryonic mesoderm cells(from epiblast)AmnionChorionEctodermMesodermEndodermYolk sacExtraembryonicmesodermAllantoisMaternalbloodvesselBlastocystreaches uterus.implants.membranesstart to form andgastrulation begins.Gastrulation has produced a three-layered embryo with fourextraembryonic membranes.1234
32Sources of developmental information for the early embryo Unfertilized egg cellMolecules ofanother cyto-plasmic deter-minantMolecules of aa cytoplasmicdeterminantSpermFertilizationZygote(fertilized egg)Mitotic cell divisionTwo-celledembryoCytoplasmic determinants in the egg. The unfertilized egg cell has molecules in its cytoplasm,encoded by the mother’s genes, that influence development. Many of these cytoplasmicdeterminants, like the two shown here, are unevenly distributed in the egg. After fertilizationand mitotic division, the cell nuclei of the embryo are exposed to different sets of cytoplasmicdeterminants and, as a result, express different genes.(a)Nucleus
33chemicals that signal nearby cells to change their gene expression. Induction by nearby cells. The cells at the bottom of the early embryo depicted here are releasingchemicals that signal nearby cells to change their gene expression.Early embryo(32 cells)NUCLEUSSignaltransductionpathwayreceptormolecule(inducer)(b)
34Cell signaling and induction during development of the nematode AnteriorEMBRYOPosteriorReceptorSignalproteindaughtercell of 3Will go on toform muscleand gonadsform adultintestine1243EpidermisGonadAnchor cellVulval precursor cellsInner vulvaOuter vulvaADULTInduction of the intestinal precursor cell at thefour-cell stage.Induction of vulval cell types during larvaldevelopment.(a)(b)
35The effect of the bicoid gene, a maternal effect (egg-polarity) gene in Drosophila TailHeadWild-type larvaMutant larva (bicoid)Drosophila larvae with wild-type and bicoid mutant phenotypes. A mutationin the mother’s bicoid gene leads to tail structures at both ends (bottom larva).The numbers refer to the thoracic and abdominal segments that are present.(a)T1T2T3A1A2A3A4A5A6A7A8
36Translation of bicoid mRNA FertilizationNurse cellsEgg cellbicoid mRNADevelopingegg cellBicoid mRNAin matureunfertilized egg100 µmBicoid protein inearly embryoAnterior end(b) Gradients of bicoid mRNA and bicoid protein in normal egg and early embryo.123
37Conservation of homeotic genes in a fruit fly and a mouse Adultfruit flyFruit fly embryo(10 hours)FlychromosomeMousechromosomesMouse embryo(12 days)Adult mouse
38Effect of differences in Hox gene expression during development in crustaceans and insects ThoraxGenitalsegmentsAbdomen
39Mutant Drosophila with an extra small eye on its antenna
40Vertebrate limb development Limb budAnteriorAERZPAPosteriorApicalectodermalridge50 µmDigitsVentralDistalProximalDorsalOrganizer regions. Vertebrate limbs develop fromprotrusions called limb buds, each consisting ofmesoderm cells covered by a layer of ectoderm.Two regions, termed the apical ectodermal ridge(AER, shown in this SEM) and the zone of polarizingactivity (ZPA), play key organizer roles in limbpattern formation.Wing of chick embryo. As the bud develops into alimb, a specific pattern of tissues emerges. In thechick wing, for example, the three digits are alwayspresent in the arrangement shown here. Patternformation requires each embryonic cell to receivesome kind of positional information indicatinglocation along the three axes of the limb. The AERand ZPA secrete molecules that help provide thisinformation.(b)(a)
41anterior margin of a recipient chick limb bud. What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates?ZPA tissue from a donor chick embryo was transplanted under the ectoderm in theanterior margin of a recipient chick limb bud.EXPERIMENTAnteriorNew ZPADonorlimbbudHostlimbbudZPAPosteriorIn the grafted host limb bud, extra digits developed from host tissue in a mirror-imagearrangement to the normal digits, which also formed (see Figure 47.26b for a diagram of a normalchick wing).RESULTSThe mirror-image duplication observed in this experiment suggests that ZPA cells secretea signal that diffuses from its source and conveys positional information indicating “posterior.” As thedistance from the ZPA increases, the signal concentration decreases and hence more anterior digits develop.CONCLUSION
42Sex determination Zygote Sperm Develop in early embryo Y Testes Ovum XYXSRYSeminiferoustubulesIndifferentgonadsLeydig cellsXNo SRYOvariesOvumXX(Follicles do notdevelop untilthird trimester)XSpermZygote
48Human fetal development The fetus just spends much of the 2nd & 3rd trimesters just growing…and doing various flip-turns & kicks inside amniotic fluidWeek 20
49Human fetal development 24 weeks (6 months; 2nd trimester)fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix
50Human fetal development 30 weeks (7.5 months)umbilical cord
51Getting crowded in there!! 32 weeks (8 months)The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming
52Birth positive feedback Estrogen Oxytocin from ovaries from fetus and mother'sposterior pituitaryInduces oxytocinreceptors on uterusStimulates uterusto contractStimulatesplacenta to makeProstaglandinsStimulate morecontractionsof uterusPositive feedback
53And you think 9 months of AP Bio is hard! The end of the journey!And you think 9 months of AP Bio is hard!
54Mechanisms of some contraceptive methods MaleFemaleMethodEventProduction ofviable spermviable oocytesVasectomyCombinationbirth controlpill (or injection,patch, orvaginal ring)Sperm transportdown maleduct systemOvulationAbstinenceCondomCoitusinterruptus(very highfailure rate)Spermdepositedin vaginaCapture of theoocyte by theoviductTubal ligationSpermicides;diaphragm;cervical cap;progestin alone(minipill, implant,or injection)movementthroughfemalereproductivetractTransportof oocyte inMeeting of sperm and oocytein oviductMorning-afterpill (MAP)Union of sperm and eggImplantation of blastocystin properly preparedendometriumBirthProgestin alone
55Reproductive Cloning of a Mammal by Nuclear Transplantation NucleusremovedMammarycell donorEgg celldonorfrom ovaryCulturedmammary cellsare semistarved,arresting the cellcycle and causingdedifferentiationNucleus frommammary cellGrown in cultureEarly embryoImplanted in uterusof a third sheepSurrogatemotherEmbryonicdevelopmentLamb (“Dolly”)genetically identical tomammary cell donor456123Cells fusedAPPLICATIONThis method is used to produce clonedanimals whose nuclear genes are identical to the donoranimal supplying the nucleus.TECHNIQUEShown here is the procedure used to produceDolly, the first reported case of a mammal cloned using the nucleusof a differentiated cell.RESULTSThe cloned animal is identical in appearanceand genetic makeup to the donor animal supplying the nucleus,but differs from the egg cell donor and surrogate mother.
57Working with stem cells Embryonic stem cellsAdult stem cellsEarly human embryoat blastocyst stage(mammalian equiva-lent of blastula)From bone marrowin this exampleTotipotentcellsPluripotentCulturedstem cellsDifferentcultureconditionstypes ofdifferentiatedLiver cellsNerve cellsBlood cells
59Make sure you can do the following: Label all parts of the male and female reproductive systems and explain how they contribute to the functions of the systems.Explain the major phases of animal development.Demonstrate how reproductive technologies might have moral and ethical implications for societyExplain the causes of reproductive system disruptions and how disruptions of the reproductive system can lead to disruptions of homeostasis.