2 The 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
4 How Many Kingdoms? Extant 8 5 3 Extinct 2 Long Time with 1 ArchaebacteriaArchezoansMulticellular AnimalsProtozoansGreen AlgaeBryophytesTracheophytesSlime MoldsMyxozoansTrue FungiBacteriaEuglenoidsChrysophytesBrown AlgaeRed algae853Extinct21Long Time withProkaryotes onlyOriginal Cell
5 Rhodophyta Photosynthetic, mostly marine red algae Odd features Body multicellular, supported by water, so simple thallusThallus attached to substrate by holdfastRarely pelagic (floating)Chloroplasts have three membranes (secondary endosymbiont)Photosynthetic pigments: chlorophyll a, phycoerythrin, phycocyanin…colors can be red, brown, purple, blue, green, blackish!Storage materials: floridean starch in cytosol (-1,4-glycan)Wall polysaccharides: cellulose and agar or carrageenanNo flagella, so centriole missingGametangia: spermatangia (male) and carpogonium (female)Some species encrust with calcium carbonate…contribute to reefs4000 species
6 CompsopogonHere are some of the example red algae some of these you should have observed in laboratory.CaloglossaPorphyridiumCallithamnion
8 Polysiphonia nigrescens Polysiphonia nigrescens Polysiphonia nigrescensPolysiphonia nigrescensbenthic (attached)filamentouscommon on New England rocky coast2N tetrasporophytetetrasporangiumtetraspore (meiospore)
9 Polysiphonia nigrescens Tetraspore (meiospore) germinates into isomorphic homothallic gametophyte (1N) thallusMale branches near the tops of the plants produce spermatangiaFemale branches near the bottom of the thallus produce carpogonia
10 Polysiphonia nigrescens marine/algae/polysiphonia%20male.jpgPolysiphonia nigrescensTetraspore (meiospore) germinates into isomorphic thallusMale branches produce spermatangia releasing spermatiaFemale branches produce carpogonium with trichogyne.Trichogyne receives spermatium (no flagellum!)spermatiumtrichogyne
11 Polysiphonia nigrescens The 2N zygote develops inside the cystocarp attached to the gametophyte (1N) thallus.The cystocarps expand and mature into carposporangiaCarposporangia release diploid carpospores which then germinate into diploid tetrasporophytes.
12 Polysiphonia Life Cycle syngamy Note: See previous slides for photo credits!spermatangiumsyngamygametes (produced by mitosis)zygote (inside cystocarp)Carposporophyte (inside cystocarp)spermatium(released to water)1N2Ncarpogoniumcarpospore(released to watersettles to substrategrows by mitosis)trichogynecystocarpTetrasporophyteGametophyte isomorphichomothallictetrasporangiumtetrasporocytetetraspore(released to watersettles to substrate grows by mitosis)meiosis
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