2The Organism as a Unit of Life Looking Back at Bio 115The Organism as a Unit of LifeCellular Structure (cell = unit of life)…one or many!Metabolism = Homeostasis (PSN, Resp, N2fix, ferment, etc.)Growth = irreversible change in sizeReproduction…failure = extinctionAcclimatization-short term responses = behaviorAdaptation-long term responses = evolution
4How Many Kingdoms? Extant 8 Still needs refining! Protista appears 5 3 Multicellular AnimalsMyxozoansProtozoansTracheophytesBryophytesTrue FungiSlime MoldsRed algaeBrown AlgaeGreen AlgaeChrysophytesEuglenoidsArchezoansArchaebacteriaBacteriaProtistarefined8Still needs refining!Protista appears53Extinct21Long Time withProkaryotes onlyOriginal Cell
5Mycetozoans “True and Cellular Slime Molds” Somewhere between protists and fungiPredatory amoeboid feeding upon bacteria, usually in decaying materialEngulfing feedingReproduction via spores500 speciesTwo Major Classes:Myxogastrea (True slime molds: Physarum)Dictyostelea (Cellular slime molds: Dictyostelium)
6Physarum polycephalum True Slime MoldHaploid (1N) spores germinate in rotting vegetationFlagellated gametes emerge and undergo syngamyDiploid (2N) zygote amoeboid cell feeds on bacteriaMitosis without cytokinesis makes multinucleate plasmodiumCytoplasm migrates by streamingDevelops into fruiting body undergoing meiosis to make haploid spores
7Physarum polycephalum True Slime MoldThis portion of the plasmodium is showing the amoeboid movement of the cytoplasm.The plasmodium engulfs bacteria by endocytosis into food vacuoles for digestionFoodVacuolesNucleiThe plasmodium is multinucleate, and each nucleus is diploid (2N).
8Physarum polycephalum True Slime MoldThe plasmodium with all of those nuclei and food vacuoles, etc. shows amazingly active cytoplasmic streaming shown in this movie.The movement involves actin-myosin interactions between microfilaments of actin and myosin proteins bound to organelles.The movement relies upon Ca2+ and ATP availability.
9Physarum polycephalum True Slime MoldLooking at this sporangium, can you figure out how the specific epithet was inspired?SporangiumSporangiophoreSpores
10Physarum polycephalum True Slime MoldThe spores germinate, releasing flagellated gametes.The gametes unite in syngamy.The resulting zygote is amoeboid and begins feeding.Mitoses without cytokinesis enlarges the multinucleate zygote into a full plasmodium.SporeZygoteGametes
11Tipula oleraceae or T. paludosa Adults resemble mosquitoes because they are indeed relatives.Adults generally do not feed and live for only a few days.The larval stages are aquatic in some species or lawn soil dwelling in other species.adulteggsadultlarvapupa
12Life Cycle of Physarum polycephalum isogametesswarm cellsplasmodiumSYNGAMYno cytokinesisgameteszygotemitosisgerminationasexualreproductionmitosisThis is basically the gametic shortcut… spores become gametes… if the mitosis of myxamoebae is not considered equivalent to the production of a multicellular gametophyte.gametangiamitosisdifferentiationdifferentiationGametophyte1N2NSporophytemyxamoebaedifferentiationdifferentiationmitosissporangiumgerminationmitosissporangiumcytokinesissporessporocyte4 meiosporesMEIOSISsporocyte
13Dictyostelium discoideum Cellular Slime MoldThis is the spore produced by the sporangium.Actin rods extend the length of the spore.It is released into the wind and carried to hopefully-better environments.There it germinates to produce amoebae.
14Dictyostelium discoideum Cellular Slime MoldThe amoebae feed upon bacteria.When the bacterial supply is gone, one amoeba produces cAMP.This signals others to join together to form a multicellular pseudoplasmodium (“slug”).AdenineNNH2OHOO-OPRibose
15Dictyostelium discoideum Cellular Slime MoldThe pseudoplasmodium moves on a slime trail seeking more bacteria.If bacteria are not found, the plasmodium differentiates into sporangiophore and sporangium.
16Dictyostelium discoideum Cellular Slime MoldThe amoebae feed upon bacteria.When the bacterial supply is gone, one amoeba produces cAMP, signalling the others to join together to form a multicellular pseudoplasmodium (“slug”).The slug moves on a slime trail seeking more bacteria.If bacteria are not found, the plasmodium differentiates into sporangiophore and sporangium.The spores are shed to the wind to disperse the species.