Microbial Life: Prokaryotes and Protists - Renz Science

Chapter 16Microbial Life: Prokaryotes andProtistsFigure 16.0_1PowerPoint Lectures forCampbell Biology: Concepts & Connections, Seventh EditionReece, Taylor, Simon, and Dickey© 2012 Pearson Education, Inc. Lecture by Edward J. ZaliskoFigure 16.0_2Figure 16.0_3Chapter 16: Big IdeasProkaryotesProtists16.1 Prokaryotes are diverse and widespreadPROKARYOTES Prokaryotic cells are smaller than eukaryotic cells.– Prokaryotes range from 1–5 µm in diameter.– Eukaryotes range from 10–100 µm in diameter. The collective biomass of prokaryotes is at least 10times that of all eukaryotes.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.1

Figure 16.116.1 Prokaryotes are diverse and widespread Prokaryotes live in habitats– too cold,– too hot,– too salty,– too acidic, and– too alkaline for eukaryotes to survive. Some bacteria are pathogens, causing disease.But most bacteria on our bodies are benign orbeneficial.© 2012 Pearson Education, Inc.16.1 Prokaryotes are diverse and widespread Several hundred species of bacteria live in and onour bodies,– decomposing dead skin cells,– supplying essential vitamins, and– guarding against pathogenic organisms. Prokaryotes in soil decompose dead organisms,sustaining chemical cycles.16.2 External features contribute to the success ofprokaryotes Prokaryotic cells have three common cell shapes.– Cocci are spherical prokaryotic cells. They sometimesoccur in chains that are called streptococci.– Bacilli are rod-shaped prokaryotes. Bacilli may also bethreadlike, or filamentous.– Spiral prokaryotes are like a corkscrew.– Short and rigid prokaryotes are called spirilla.– Longer, more flexible cells are called spirochetes.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.Figure 16.2AFigure 16.2A_1Cocci Bacilli SpirocheteCocci2

Figure 16.2A_2Figure 16.2A_3SpirocheteBacilli16.2 External features contribute to the success ofprokaryotesFigure 16.2B Nearly all prokaryotes have a cell wall. Cell walls– provide physical protection and– prevent the cell from bursting in a hypotonicenvironment. When stained with Gram stain, cell walls ofbacteria are either– Gram-positive, with simpler cell walls containingpeptidoglycan, or– Gram-negative, with less peptidoglycan, and morecomplex and more likely to cause disease.© 2012 Pearson Education, Inc.16.2 External features contribute to the success ofprokaryotesFigure 16.2C The cell wall of many prokaryotes is covered by acapsule, a sticky layer of polysaccharides orprotein. The capsule– enables prokaryotes to adhere to their substrate or toother individuals in a colony and– shields pathogenic prokaryotes from attacks by a host’simmune system.CapsuleTonsil cellBacterium© 2012 Pearson Education, Inc.3

16.2 External features contribute to the success ofprokaryotesFigure 16.2D Some prokaryotes have external structures thatextend beyond the cell wall.Flagella– Flagella help prokaryotes move in their environment.– Hairlike projections called fimbriae enable prokaryotesto stick to their substrate or each other.Fimbriae© 2012 Pearson Education, Inc.16.3 Populations of prokaryotes can adapt rapidlyto changes in the environment Prokaryote population growth– occurs by binary fission,– can rapidly produce a new generation within hours, and– can generate a great deal of genetic variation– by spontaneous mutations,– increasing the likelihood that some members of the populationwill survive changes in the environment.16.3 Populations of prokaryotes can adapt rapidlyto changes in the environment The genome of a prokaryote typically– has about one-thousandth as much DNA as aeukaryotic genome and– is one long, circular chromosome packed into a distinctregion of the cell. Many prokaryotes also have additional small,circular DNA molecules called plasmids, whichreplicate independently of the chromosome.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.Figure 16.3AChromosomePlasmids16.3 Populations of prokaryotes can adapt rapidlyto changes in the environment Some prokaryotes form specialized cells calledendospores that remain dormant through harshconditions. Endospores can survive extreme heat or cold.© 2012 Pearson Education, Inc.4

Figure 16.3B16.4 Prokaryotes have unparalleled nutritionaldiversityEndospore Prokaryotes exhibit much more nutritional diversitythan eukaryotes. Two sources of energy are used.– Phototrophs capture energy from sunlight.– Chemotrophs harness the energy stored in chemicals.© 2012 Pearson Education, Inc.16.4 Prokaryotes have unparalleled nutritionaldiversity Two sources of carbon are used by prokaryotes.– Autotrophs obtain carbon atoms from carbon dioxide.– Heterotrophs obtain their carbon atoms from theorganic compounds present in other organisms.16.4 Prokaryotes have unparalleled nutritionaldiversity The terms that describe how prokaryotes obtainenergy and carbon are combined to describe theirmodes of nutrition.– Photoautotrophs obtain energy from sunlight and usecarbon dioxide for carbon.– Photoheterotrophs obtain energy from sunlight but gettheir carbon atoms from organic molecules.– Chemoautotrophs harvest energy from inorganicchemicals and use carbon dioxide for carbon.– Chemoheterotrophs acquire energy and carbon fromorganic molecules.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.Figure 16.4Figure 16.4_1SunlightPhotoautotrophsENERGY SOURCEChemicalsChemoautotrophsCARBON SOURCEOrganic compounds CO 2OscilliatoriaPhotoheterotrophsRhodopseudomonasUnidentified “rock-eating” bacteriaChemoheterotrophsA Bdellovibrio attacking alarger cellPhotoautotrophsOscilliatoria5

Figure 16.4_2Figure 16.4_3PhotoheterotrophsChemoautotrophsUnidentified “rock-eating” bacteriaRhodopseudomonasFigure 16.4_4ChemoheterotrophsA Bdellovibrio attacking a larger cell16.5 CONNECTION: Biofilms are complexassociations of microbes Biofilms– are complex associations of one or several species ofprokaryotes and– may also include protists and fungi. Prokaryotes attach to surfaces and form biofilmcommunities that– are difficult to eradicate and– may cause medical and environmental problems.© 2012 Pearson Education, Inc.16.5 CONNECTION: Biofilms are complexassociations of microbes Biofilms are large and complex “cities” of microbesthat– communicate by chemical signals,– coordinate a division of labor and defense againstinvaders, and– use channels to distribute nutrients and collect wastes.16.5 CONNECTION: Biofilms are complexassociations of microbes Biofilms that form in the environment can bedifficult to eradicate. Biofilms– clog and corrode pipes,– gum up filters and drains, and– Coat the hulls of ships.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.6

Figure 16.516.6 CONNECTION: Prokaryotes help clean upthe environment Prokaryotes are useful for cleaning up contaminantsin the environment because prokaryotes– have great nutritional diversity,– are quickly adaptable, and– can form biofilms.© 2012 Pearson Education, Inc.16.6 CONNECTION: Prokaryotes help clean upthe environment Bioremediation is the use of organisms to removepollutants from– soil,– air, or– water.16.6 CONNECTION: Prokaryotes help clean upthe environment Prokaryotic decomposers are the mainstays ofsewage treatment facilities.– Raw sewage is first passed through a series of screensand shredders.– Solid matter then settles out from the liquid waste,forming sludge.– Sludge is gradually added to a culture of anaerobicprokaryotes, including bacteria and archaea.– The microbes decompose the organic matter into materialthat can be placed in a landfill or used as fertilizer.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.16.6 CONNECTION: Prokaryotes help clean upthe environmentFigure 16.6A Liquid wastes are treated separately from thesludge.– Liquid wastes are sprayed onto a thick bed of rocks.– Biofilms of aerobic bacteria and fungi growing on therocks remove much of the dissolved organic material.– Fluid draining from the rocks is sterilized and thenreleased, usually into a river or ocean.Rotatingspray armRock bed coatedwith aerobicprokaryotesand fungi© 2012 Pearson Education, Inc.Liquid wastesOutflow7

Figure 16.6A_1Figure 16.6A_2Rotatingspray armRock bed coatedwith aerobicprokaryotesand fungiLiquid wastesOutflowRotatingspray armRock bed coated withaerobic prokaryotesand fungi16.6 CONNECTION: Prokaryotes help clean upthe environmentFigure 16.6B Bioremediation is becoming an important tool forcleaning up toxic chemicals released into the soiland water by industrial processes. Environmental engineers change the naturalenvironment to accelerate the activity of naturallyoccurring prokaryotes capable of metabolizingpollutants.© 2012 Pearson Education, Inc.16.7 Bacteria and archaea are the two mainbranches of prokaryotic evolutionTable 16.7 New studies of representative genomes ofprokaryotes and eukaryotes strongly support thethree-domain view of life.– Prokaryotes are now classified into two domains:– Bacteria and– Archaea.– Archaea have at least as much in common witheukaryotes as they do with bacteria.© 2012 Pearson Education, Inc.8

16.8 Archaea thrive in extreme environments—and in other habitatsFigure 16.8A Archaeal inhabitants of extreme environmentshave unusual proteins and other molecularadaptations that enable them to metabolize andreproduce effectively.– Extreme halophiles thrive in very salty places.– Extreme thermophiles thrive in– very hot water, such as geysers, and– acid pools.© 2012 Pearson Education, Inc.16.8 Archaea thrive in extreme environments—and in other habitatsFigure 16.8B Methanogens– live in anaerobic environments,– give off methane as a waste product from– the digestive tracts of cattle and deer and– decomposing materials in landfills.© 2012 Pearson Education, Inc.16.9 Bacteria include a diverse assemblage ofprokaryotes The domain Bacteria is currently divided into fivegroups, based on comparisons of geneticsequences. 1. Proteobacteria– are all gram negative,– share a particular rRNA sequence, and– represent all four modes of nutrition.16.9 Bacteria include a diverse assemblage ofprokaryotes– Thiomargarita namibiensis is a type of proteobacteriathat– is a giant among prokaryotes, typically ranging up to100–300 microns in diameter,– uses H 2 S to generate organic molecules from CO 2 ,and– produces sulfur wastes, seen as small greenishglobules in the following figure.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.9

Figure 16.9A16.9 Bacteria include a diverse assemblage ofprokaryotes– Proteobacteria also include Rhizobium species that– live symbiotically in root nodules of legumes and– convert atmospheric nitrogen gas into a form usableby their legume host.– Symbiosis is a close association betweenorganisms of two or more species.– Rhizobium is an endosymbiont, living within anotherspecies.© 2012 Pearson Education, Inc.Figure 32.13B16.9 Bacteria include a diverse assemblage ofprokaryotesShoot 2. Gram-positive bacteria– rival proteobacteria in diversity andBacteria withinNodulesvesicle in anRootsinfected cell– include the actinomycetes common in soil.– Streptomyces is often cultured by pharmaceuticalcompanies as a source of many antibiotics.© 2012 Pearson Education, Inc.Figure 16.9B16.9 Bacteria include a diverse assemblage ofprokaryotes 3. Cyanobacteria– Cyanobacteria are the only group of prokaryotes withplantlike, oxygen-generating photosynthesis.– Some species, such as Anabaena, have specializedcells that fix nitrogen.© 2012 Pearson Education, Inc.10

Figure 16.9C16.9 Bacteria include a diverse assemblage ofprokaryotesPhotosyntheticcellsNitrogen-fixingcells 4. Chlamydias– Chlamydias live inside eukaryotic host cells.– Chlamydia trachomatis– is a common cause of blindness in developingcountries and– is the most common sexually transmitted disease inthe United States.© 2012 Pearson Education, Inc.Figure 16.9D16.9 Bacteria include a diverse assemblage ofprokaryotes 5. Spirochetes are– helical bacteria and– notorious pathogens, causing– syphilis and– Lyme disease.© 2012 Pearson Education, Inc.Figure 16.9E16.10 CONNECTION: Some bacteria causedisease All organisms are almost constantly exposed topathogenic bacteria. Most bacteria that cause illness do so by producinga poison.– Exotoxins are proteins that bacterial cells secrete intotheir environment.– Endotoxins are components of the outer membrane ofgram-negative bacteria.© 2012 Pearson Education, Inc.11

Figure 16.1016.11 SCIENTIFIC DISCOVERY: Koch’spostulates are used to prove that abacterium causes a disease Koch’s postulates are four essential conditions usedto establish that a certain bacterium is the cause of adisease. They are1. find the bacterium in every case of the disease,2. isolate the bacterium from a person who has the diseaseand grow it in pure culture,3. show that the cultured bacterium causes the diseasewhen transferred to a healthy subject, and4. isolate the bacterium from the experimentally infectedsubject.© 2012 Pearson Education, Inc.16.11 SCIENTIFIC DISCOVERY: Koch’spostulates are used to prove that abacterium causes a diseaseFigure 16.11 Koch’s postulates were used to demonstrate thatthe bacterium Helicobacter pylori is the cause ofmost peptic ulcers. The 2005 Nobel Prize in Medicine was awarded toBarry Marshall and Robin Warren for thisdiscovery.© 2012 Pearson Education, Inc.16.12 CONNECTION: Bacteria can be used asbiological weaponsFigure 16.12 Bacteria that cause anthrax and the plague can beused as biological weapons.– Bacillus anthracis killed five people in the United Statesin 2001.– Yersinia pestis bacteria– are typically carried by rodents and transmitted by fleas,causing the plague and– can cause a pneumonic form of plague if inhaled.© 2012 Pearson Education, Inc.12

16.12 CONNECTION: Bacteria can be used asbiological weapons Clostridium botulinum produces the exotoxinbotulinum, the deadliest poison on earth.PROTISTS Botulinum blocks transmission of nerve signals andprevents muscle contraction.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.16.13 Protists are an extremely diverse assortmentof eukaryotes Protists– are a diverse collection of mostly unicellular eukaryotes,– may constitute multiple kingdoms within the Eukarya,and– refer to eukaryotes that are not– plants,– animals, or– fungi.16.13 Protists are an extremely diverse assortmentof eukaryotes Protists obtain their nutrition in many ways. Protistsinclude– autotrophs, called algae, producing their food byphotosynthesis,– heterotrophs, called protozoans, eating bacteria andother protists,– heterotrophs, called parasites, deriving their nutritionfrom a living host, and– mixotrophs, using photosynthesis and heterotrophy.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.Figure 16.13AFigure 16.13A_1AutotrophyAutotrophyHeterotrophyMixotrophyCaulerpa, a green algaGiardia, a parasiteEuglenaCaulerpa, a green alga13

Figure 16.13A_2Figure 16.13A_3HeterotrophyMixotrophyGiardia, a parasiteEuglena16.13 Protists are an extremely diverse assortmentof eukaryotesFigure 16.13B Protists are found in many habitats including– anywhere there is moisture and– the bodies of host organisms.© 2012 Pearson Education, Inc.Figure 16.13B_1Figure 16.13B_214

16.13 Protists are an extremely diverse assortmentof eukaryotes Recent molecular and cellular studies indicate thatnutritional modes used to categorize protists do notreflect natural clades. Protist phylogeny remains unclear. One hypothesis, used here, proposes fivemonophyletic supergroups.16.14 EVOLUTION CONNECTION: Secondaryendosymbiosis is the key to much of protistdiversity The endosymbiont theory explains the origin ofmitochondria and chloroplasts.– Eukaryotic cells evolved when prokaryotes establishedresidence within other, larger prokaryotes.– This theory is supported by present-day mitochondria andchloroplasts that– have structural and molecular similarities toprokaryotic cells and– replicate and use their own DNA, separate from thenuclear DNA of the cell.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.Figure 16.14_s1Figure 16.14_s2PrimaryendosymbiosisCyanobacteriumEvolved intochloroplastPrimaryendosymbiosisChloroplastEvolved intoCyanobacterium chloroplastGreen alga1 NucleusHeterotrophiceukaryote21 NucleusHeterotrophiceukaryote23 AutotrophiceukaryotesChloroplastRed algaFigure 16.14_s3PrimaryendosymbiosisChloroplastEvolved intoCyanobacterium chloroplast1 NucleusHeterotrophiceukaryote2Green alga3 AutotrophiceukaryotesChloroplastRed alga4 Heterotrophiceukaryotes16.14 EVOLUTION CONNECTION: Secondaryendosymbiosis is the key to much of protistdiversity Secondary endosymbiosis is– the process in which an autotrophic eukaryotic protistbecame endosymbiotic in a heterotrophic eukaryoticprotist and– key to protist diversity.© 2012 Pearson Education, Inc.15

Figure 16.14_s4Figure 16.14_s5PrimaryendosymbiosisChloroplastEvolved intoCyanobacterium chloroplastGreen algaSecondaryendosymbiosisPrimaryendosymbiosisChloroplastEvolved intoCyanobacterium chloroplastGreen algaSecondaryendosymbiosisRemnant ofgreen algaEuglena1 NucleusHeterotrophiceukaryote23 Autotrophiceukaryotes4 Heterotrophiceukaryotes51 NucleusHeterotrophiceukaryote23 Autotrophiceukaryotes4 Heterotrophiceukaryotes5ChloroplastRed algaChloroplastRed alga16.15 Chromalveolates represent the range ofprotist diversityFigure 16.15A Chromalveolates include– diatoms, unicellular algae with a glass cell wallcontaining silica,© 2012 Pearson Education, Inc.16.15 Chromalveolates represent the range ofprotist diversityFigure 16.15B Chromalveolates include– diatoms, unicellular algae with a glass cell wallcontaining silica,– dinoflagellates, unicellular autotrophs, heterotrophs,and mixotrophs that are common components of marineplankton,© 2012 Pearson Education, Inc.16

16.15 Chromalveolates represent the range ofprotist diversityFigure 16.15C Chromalveolates include– diatoms, unicellular algae with a glass cell wallcontaining silica,– dinoflagellates, unicellular autotrophs, heterotrophs,and mixotrophs that are common components of marineplankton,– brown algae, large, multicellular autotrophs,© 2012 Pearson Education, Inc.16.15 Chromalveolates represent the range ofprotist diversityFigure 16.15D Chromalveolates include– diatoms, unicellular algae with a glass cell wallcontaining silica,– dinoflagellates, unicellular autotrophs, heterotrophs,and mixotrophs that are common components of marineplankton,– brown algae, large, multicellular autotrophs,– water molds, unicellular heterotrophs,© 2012 Pearson Education, Inc.16.15 Chromalveolates represent the range ofprotist diversityFigure 16.15E Chromalveolates include– diatoms, unicellular algae with a glass cell wallcontaining silica,Mouth– dinoflagellates, unicellular autotrophs, heterotrophs,and mixotrophs that are common components of marineplankton,– brown algae, large, multicellular autotrophs,– water molds, unicellular heterotrophs,– ciliates, unicellular heterotrophs and mixotrophs thatuse cilia to move and feed,© 2012 Pearson Education, Inc.17

16.15 Chromalveolates represent the range ofprotist diversity Chromalveolates include– diatoms, unicellular algae with a glass cell wallcontaining silica,– dinoflagellates, unicellular autotrophs, heterotrophs,and mixotrophs that are common components of marineplankton,– brown algae, large, multicellular autotrophs,– water molds, unicellular heterotrophs,– ciliates, unicellular heterotrophs and mixotrophs that usecilia to move and feed, and– a group including parasites, such as Plasmodium, whichcauses malaria.16.16 CONNECTION: Can algae provide arenewable source of energy? Fossil fuels– are the organic remains of organisms that livedhundreds of millions of years ago and– primarily consist of– diatoms and– primitive plants.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.16.16 CONNECTION: Can algae provide arenewable source of energy?Figure 16.16 Lipid droplets in diatoms and other algae mayserve as a renewable source of energy. If unicellular algae could be grown on a large scale,this oil could be harvested and processed intobiodiesel. Numerous technical hurdles remain beforeindustrial-scale production of biofuel from algaebecomes a reality.© 2012 Pearson Education, Inc.16.17 Rhizarians include a variety of amoebas16.17 Rhizarians include a variety of amoebas The two largest groups of Rhizaria are among theorganisms referred to as amoebas. Amoebas move and feed by means ofpseudopodia, temporary extensions of the cell. Foraminiferans– are found in the oceans and in fresh water,– have porous shells, called tests, composed of calciumcarbonate, and– have pseudopodia that function in feeding andlocomotion.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.18

Figure 16.17AFigure 16.17A_1Figure 16.17A_216.17 Rhizarians include a variety of amoebas Radiolarians– are mostly marine and– produce a mineralized internal skeleton made of silica.© 2012 Pearson Education, Inc.Figure 16.17B16.18 Some excavates have modified mitochondria Excavata has recently been proposed as a cladeon the basis of molecular and morphologicalsimilarities. The name refers to an “excavated” feeding groovepossessed by some members of the group. Excavates– have modified mitochondria that lack functional electrontransport chains and– use anaerobic pathways such as glycolysis to extractenergy.© 2012 Pearson Education, Inc.19

16.18 Some excavates have modified mitochondriaFigure 16.13B Excavates include– heterotrophic termite endosymbionts© 2012 Pearson Education, Inc.16.18 Some excavates have modified mitochondriaFigure 16.13A_3Mixotrophy Excavates include– heterotrophic termite endosymbionts,– autotrophic species,– mixotrophs such as EuglenaEuglena© 2012 Pearson Education, Inc.16.18 Some excavates have modified mitochondriaFigure 16.13A Excavates includeAutotrophyHeterotrophyMixotrophy– heterotrophic termite endosymbionts,– autotrophic species,– mixotrophs such as Euglena,– the common waterborne parasite Giardia intestinalis,Caulerpa, a green algaGiardia, a parasiteEuglena© 2012 Pearson Education, Inc.20

16.18 Some excavates have modified mitochondriaFigure 16.18A Excavates include– heterotrophic termite endosymbionts,– autotrophic species,– mixotrophs such as Euglena,– the common waterborne parasite Giardia intestinalis,– the parasite Trichomonas vaginalis, which causes 5million new infections each year of human reproductivetracts,UndulatingmembraneFlagella© 2012 Pearson Education, Inc.16.18 Some excavates have modified mitochondriaFigure 16.18B Excavates include– heterotrophic termite endosymbionts,– autotrophic species,– mixotrophs such as Euglena,– the common waterborne parasite Giardia intestinalis,– the parasite Trichomonas vaginalis, which causes 5million new infections each year of human reproductivetracts, and– the parasite Trypanosoma, which causes sleepingsickness in humans.© 2012 Pearson Education, Inc.16.19 Unikonts include protists that are closelyrelated to fungi and animals Unikonta is a controversial grouping joining– amoebozoans and– a group that includes animals and fungi, addressed atthe end of this unit on protists.16.19 Unikonts include protists that are closelyrelated to fungi and animals Amoebozoans have lobe-shaped pseudopodia andinclude– many species of free-living amoebas,– some parasitic amoebas, and– slime molds.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.21

Figure 16.19A16.19 Unikonts include protists that are closelyrelated to fungi and animals Plasmodial slime molds– are common where there is moist, decaying organicmatter and– consist of a single, multinucleate mass of cytoplasmundivided by plasma membranes, called aplasmodium.© 2012 Pearson Education, Inc.Figure 16.19BFigure 16.19B_1Figure 16.19B_216.19 Unikonts include protists that are closelyrelated to fungi and animals Cellular slime molds– are common on rotting logs and decaying organicmatter and– usually exist as solitary amoeboid cells, but when foodis scarce, amoeboid cells– swarm together, forming a slug-like aggregate thatwanders around for a short time and then– forms a stock supporting an asexual reproductivestructure that produces spores.© 2012 Pearson Education, Inc.22

Figure 16.19C16.20 Archaeplastids include red algae, greenalgae, and land plants Archaeplastids include:– red algae,– green algae, and– land plants.© 2012 Pearson Education, Inc.16.20 Archaeplastids include red algae, greenalgae, and land plantsFigure 16.20A Red algae– are mostly multicellular,– contribute to the structure of coral reefs, and– are commercially valuable.© 2012 Pearson Education, Inc.16.20 Archaeplastids include red algae, greenalgae, and land plantsFigure 16.20B Green algae may be unicellular, colonial, ormulticellular.– Volvox is a colonial green algae, and– Chlamydomonas is a unicellular alga propelled by twoflagella.VolvoxChlamydomonas© 2012 Pearson Education, Inc.23

Figure 16.20B_1Figure 16.20B_2VolvoxChlamydomonas16.20 Archaeplastids include red algae, greenalgae, and land plants Ulva, or sea lettuce, is– a multicellular green alga withFigure 16.20C_s1MitosisSporesMitosisMalegametophyteGametes– a complex life cycle that includes an alternation ofgenerations that consists ofFemalegametophyte– a multicellular diploid (2n) form, the sporophyte,that alternates with– a multicellular haploid (1n) form, the gametophyte.KeyHaploid (n)Diploid (2n)© 2012 Pearson Education, Inc.Figure 16.20C_s2Figure 16.20C_s3MitosisSporesMitosisMalegametophyteGametesMitosisSporesMitosisMalegametophyteGametesFemalegametophyteMeiosisFemalegametophyteFusion ofgametesFusion ofgametesZygoteSporophyteZygoteKeyHaploid (n)Diploid (2n)MitosisKeyHaploid (n)Diploid (2n)24

Figure 16.20C_216.21 EVOLUTION CONNECTION: Multicellularityevolved several times in eukaryotes The origin of the eukaryotic cell led to anevolutionary radiation of new forms of life. Unicellular protists are much more diverse in formthan simpler prokaryotes.© 2012 Pearson Education, Inc.16.21 EVOLUTION CONNECTION: Multicellularityevolved several times in eukaryotes Multicellular organisms (seaweeds, plants,animals, and most fungi) are fundamentallydifferent from unicellular organisms.– A multicellular organism has various specialized cellsthat perform different functions and are interdependent.– All of life’s activities occur within a single cell inunicellular organisms.16.21 EVOLUTION CONNECTION: Multicellularityevolved several times in eukaryotes Multicellular organisms have evolved from threedifferent lineages:– brown algae evolved from chromalveolates,– fungi and animals evolved from unikonts, and– red algae and green algae evolved from achaeplastids.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.Figure 16.21AAncestral eukaryoteArchaeplastids UnikontsGreen algaeRed algaeOther green algaeCharophytesLand plantsAmoebozoansNucleariidsFungi16.21 EVOLUTION CONNECTION: Multicellularityevolved several times in eukaryotes One hypothesis states that two separate unikontlineages led to fungi and animals, diverging morethan 1 billion years ago. A combination of morphological and molecularevidence suggests that choanoflagellates are theclosest living protist relative of animals.KeyAll unicellularBoth unicellularand multicellularAll multicellularChoanoflagellatesAnimals© 2012 Pearson Education, Inc.25

Figure 16.21BFigure 16.21B_1Nucleariids1 billionyears agoFungiA nucleariid, closest livingprotistan relative of fungiIndividualchoanoflagellateNucleariidsChoanoflagellatesAnimalsColonialchoanoflagellateSpongecollar cellFungiA nucleariid, closest livingprotistan relative of fungiSpongeFigure 16.21B_2Figure 16.21B_3IndividualchoanoflagellateChoanoflagellatesColonialchoanoflagellateAnimalsSpongecollar cellSpongeYou should now be able toYou should now be able to1. Describe the structures and functions of the diversefeatures of prokaryotes; explain how these features havecontributed to their success.2. Explain how populations of prokaryotes can adapt rapidlyto changes in their environment.3. Describe the nutritional diversity of prokaryotes and explainthe significance of biofilms.4. Explain how prokaryotes help clean up the environment.5. Compare the characteristics of the three domains of life;explain why biologists consider Archaea to be more closelyrelated to Eukarya than to Bacteria.6. Describe the diverse types of Archaea living in extremeand moderate environments.7. Distinguish between the subgroups of the domainBacteria, noting the particular structure, special features,and habitats of each group.8. Distinguish between bacterial exotoxins and endotoxins,noting examples of each.9. Describe the steps of Koch’s postulates and explain whythey are used.10. Explain how bacteria can be used as biological weapons.© 2012 Pearson Education, Inc.© 2012 Pearson Education, Inc.26

You should now be able toFigure 16.UN0111. Describe the extremely diverse assortment of eukaryotes.12. Explain how primary endosymbiosis and secondaryendosymbiosis led to further cellular diversity.13. Describe the major protist clades noting characteristicsand examples of each.14. Describe the life cycle of Ulva, noting each form in thealternation of generations and how each is produced.15. Explain how multicellular life may have evolved ineukaryotes.Nutritional mode Energy source Carbon sourcePhotoautotrophSunlightChemoautotrophPhotoheterotrophInorganic chemicalsSunlightCO 2Organic compoundsChemoheterotroph Organic compounds© 2012 Pearson Education, Inc.Figure 16.UN02Figure 16.UN02_1ExotoxinSecreted by cellEndotoxinComponent of gramnegativeplasma membraneExotoxinSecreted by cellStaphylococcus aureusSalmonella enteritidisStaphylococcus aureusFigure 16.UN02_2Figure 16.UN03EndotoxinComponent of gramnegativeplasma membraneAncestral eukaryote(a) (c)GreenalgaeRed algaeOther green algae(b)Land plantsAmoebozoansNucleariidsSalmonella enteritidis(d)(e)(f)27