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PowerPoint Lectures for
Biology: Concepts & Connections, Sixth Edition
Campbell, Reece, Taylor, Simon, and Dickey
Chapter 16 The Origin and Evolution of Microbial
Life: Prokaryotes and Protists
Lecture by Joan Sharp
Introduction: How Ancient Bacteria Changed the World
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Virtually all metabolic pathways on Earth evolved in prokaryotic cells, before the evolution of eukaryotes
The products generated by prokaryotic metabolism changed the Earth’s atmosphere and rocks
Fossilized stromatolites from 3 billion years ago contain the fossils of photosynthetic cyanobacteria
– These bacteria produced O2 and made Earth’s atmosphere aerobic
Living stromatolites still form in the warm, shallow waters of Shark Bay, western Australia
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Introduction: How Ancient Bacteria Changed the World
PROKARYOTES
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Prokaryotes lived alone on Earth for over 1 billion years
– They remain the most numerous and widespread organisms on Earth
– The total biomass of prokaryotes is ten times that of eukaryotes
16.1 Prokaryotes are diverse and widespread
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Most prokaryotes are 1–5 µm in diameter (vs. 10–100 µm for eukaryotic cells)
More prokaryotes live in your mouth than the total number of humans that have ever lived
There are ten times as many prokaryotes living in and on your body as the number of cells in your body
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16.1 Prokaryotes are diverse and widespread
Prokaryotes live in cold, hot, salty, acidic, and alkaline habitats
Although some bacteria are pathogenic and cause disease, most bacteria on our bodies are benign or beneficial
– Several hundred species of bacteria live in and on our bodies, decomposing dead skin cells, supplying essential vitamins, and guarding against pathogenic organisms
Prokaryotes in soil decompose dead organisms, sustaining chemical cycles
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16.1 Prokaryotes are diverse and widespread
The two prokaryotic domains, Bacteria and Archaea, diverged soon after life on Earth arose
Present day Archaea and Eukarya evolved from a common ancestor, complicated by gene transfer between prokaryotic lineages
Some genes of Archaea are similar to bacterial genes, some are similar to eukaryotic genes, and some are unique to Archaea
16.2 Bacteria and archaea are the two main branches of prokaryotic evolution
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Prokaryotic cell walls maintain cell shape, provide physical protection, and prevent the cell from bursting in a hypotonic environment
– In a hypertonic environment, most prokaryotes lose water and shrink away from their wall
The cell walls of Archaea and Bacteria differ
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16.4 Various structural features contribute to the success of prokaryotes
Video: Prokaryotic Flagella (Salmonella typhimurium)
Bacterial cell walls can be distinguished with a gram stain
– Gram-positive bacteria have simple walls with a thick layer of peptidoglycan
– Gram-negative bacteria have complex walls with less peptidoglycan and an outer membrane of lipids bonded to carbohydrates
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16.4 Various structural features contribute to the success of prokaryotes
Capsule
Some prokaryotes stick to the substrate or each other with hair-like appendages called pili
Sex pili join prokaryotes during conjugation
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16.4 Various structural features contribute to the success of prokaryotes
Pili
The flagella of Bacteria and Archaea allow them to move in response to chemical and physical signals in their environment
The prokaryotic flagellum is a naked protein without microtubules
– The flagellum rotates like a propeller
Are prokaryotic flagella homologous or analogous to eukaryotic flagella?
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16.4 Various structural features contribute to the success of prokaryotes
Plasmamembrane
Rotary movement ofeach flagellum
Flagellum
Cell wall
Some prokaryotes can withstand harsh conditions by forming endospores within an outer cell
– The endospore has a thick protective coat
– It can dehydrate and is tolerant of extreme heat or cold
When conditions improve, the endospore absorbs water and resumes growth, sometimes after centuries
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16.4 Various structural features contribute to the success of prokaryotes
Endospore
Some prokaryotic cells have specialized membranes that perform metabolic functions
– Aerobic prokaryotes carry out cellular respiration on infoldings of the plasma membrane
– Where is cellular respiration carried out in a eukaryote?
– Cyanobacteria carry out photosynthesis on infolded thylakoid membranes
– Where is photosynthesis carried out in a photosynthetic eukaryote?
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16.4 Various structural features contribute to the success of prokaryotes
Respiratory
membrane
Thylakoid
membrane
Prokaryotic DNA forms a circular chromosome
– Smaller rings of DNA called plasmids carry genes that may provide resistance to antibiotics or metabolize rare nutrients, among other metabolic activities
Many prokaryotes can transfer genes, such as antibiotic resistance genes, within or between species
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16.4 Various structural features contribute to the success of prokaryotes
CO2
Organiccompounds
Energy source
Chemical
ChemoautotrophsPhotoautotrophs
ChemoheterotrophsPhotoheterotrophs
Light
Carbonsource
In some prokaryotes, metabolic cooperation occurs in surface-coating colonies called biofilms
– Biofilms form when cells in a colony secrete signaling molecules that recruit nearby cells
– Channels in the biofilm allow nutrients and wastes to move inside and outside the biofilm
Biofilms cause ear and urinary tract infections and the dental plaque that produces tooth decay
16.5 Prokaryotes obtain nourishment in a variety of ways
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Archaea are among the most abundant cells on Earth
They are a major life-form in the oceans
16.6 Archaea thrive in extreme environments—and in other habitats
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Video: Tubeworms
Clades of gram-negative bacteria
– Alpha proteobacteria
– Rhizobium species live in legume nodules and fix atmospheric N2
– Photosynthetic gamma proteobacteria
– Sulfur bacteria oxidize H2S
16.7 Bacteria include a diverse assemblage of prokaryotes
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Clades of gram-negative bacteria
– Delta proteobacteria
– Myxobacteria form elaborate colonies and congregate into fruiting bodies that release resistant spores
– Chlamydias live inside eukaryotic host cells
– Chlamydias cause blindness and sexually transmitted disease
– Spirochetes are helical bacteria
– Spirochetes cause syphilis and Lyme disease
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16.7 Bacteria include a diverse assemblage of prokaryotes
Video: Cyanobacteria (Oscillatoria)
Nitrogen-fixingcells
Photosyntheticcells
Clades of gram-positive bacteria
– Actinomycetes are common soil bacteria that decompose organic matter
– Streptomyces is a source of many antibiotics
– Mycoplasmas lack cell walls
– They are the tiniest of all known cells, with diameters as small as 0.1 µm (about 5 times the size of a ribosome)
– Cyanobacteria carry out oxygen-generating photosynthesis
– Ancient cyanobacteria formed stromatolites that made the atmosphere aerobic
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16.7 Bacteria include a diverse assemblage of prokaryotes
Pathogenic bacteria cause disease by producing poisonous exotoxins or endotoxins
– Exotoxins are proteins secreted by bacterial cells
– Some of the most powerful toxins known are exotoxins, including the toxin that causes lockjaw
– Staphylococcus aureus produces several exotoxins, including one that causes deadly toxic shock syndrome
16.8 CONNECTION: Some bacteria cause disease
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Endotoxins are components of the outer membrane of gram-negative bacteria, released when the cell dies or is digested by a defensive cell
– Endotoxins produce septic shock, bacterial meningitis, and food poisoning
– The most widespread pest-carried disease in the United States is Lyme disease, caused by the spirochaete Borrelia burgdorferi
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16.8 CONNECTION: Some bacteria cause disease
Spirochetethat causesLyme disease
Tick thatcarriesthe Lymediseasebacterium
“Bull’s-eye” rash
Spirochetethat causesLyme disease
Tick thatcarriesthe Lymediseasebacterium
“Bull’s-eye” rash
The bacterium that causes anthrax can be used as biological weapons
– Bacillus anthracis forms hardy endospores
– Weaponizing anthrax involves manufacturing endospores that disperse easily in air, where they are inhaled and germinate in the lungs
The Biological Weapons Convention has been signed by 103 nations, who have pledged never to develop or store biological weapons
16.9 CONNECTION: Bacteria can be used as biological weapons
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Prokaryotes are key participants in chemical cycles, making nitrogen available to plants and thus animals
They also decompose organic wastes and dead organisms to inorganic chemicals
Bioremediation is the use of organisms to remove pollutants from soil, air, or water
– Prokaryotes are decomposers in sewage treatment and can clean up oil spills and toxic mine wastes
16.10 CONNECTION: Prokaryotes help recycle chemicals and clean up the environment
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Liquid wastes
Rotatingspray arm
Outflow
Rock bedcoated withaerobicbacteriaand fungi
Liquid wastes
Rotatingspray arm
Outflow
Rock bedcoated withaerobicbacteriaand fungi
PROTISTS
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Protists constitute several kingdoms within the domain Eukarya
Protists obtain their nutrition in a variety of ways
– Algae are autotrophic protists
– Protozoans are heterotrophic protists, eating bacteria and other protists
– Fungus-like protists obtain organic molecules by absorption
16.11 Protists are an extremely diverse assortment of eukaryotes
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Symbiosis is a close association between organisms of two or more species
– Endosymbiosis—living within another
– Termite endosymbionts digest cellulose in the wood eaten by the host
– The protists have endosymbiotic prokaryotes that metabolize the cellulose
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16.11 Protists are an extremely diverse assortment of eukaryotes
Protists are eukaryotes, with
– Membrane-bound chromosomes
– Multiple chromosomes
– Flagella or cilia with 9 + 2 pattern of microtubules
Some protists have a very high level of cellular complexity
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16.11 Protists are an extremely diverse assortment of eukaryotes
What is the origin of the enormous diversity of protists?
– Complex eukaryotic cells evolved when prokaryotes took up residence within larger prokaryotes
16.12 EVOLUTION CONNECTION: Secondary endosymbiosis is the key to protist diversity
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Nucleus
Primaryendosymbiosis
Cyanobacterium
Heterotrophiceukaryote
Evolved intochloroplast
Nucleus
Primaryendosymbiosis
Cyanobacterium
Heterotrophiceukaryote
Evolved intochloroplast
Autotrophiceukaryotes
Nucleus
Nucleus
Chloroplast
Green alga
ChloroplastRed alga
Nucleus
Primaryendosymbiosis
Cyanobacterium
Heterotrophiceukaryote
Evolved intochloroplast
Autotrophiceukaryotes
Nucleus
Nucleus
Chloroplast
Green alga
ChloroplastRed alga
Heterotrophiceukaryotes
Nucleus
Primaryendosymbiosis
Cyanobacterium
Heterotrophiceukaryote
Evolved intochloroplast
Autotrophiceukaryotes
Nucleus
Nucleus
Chloroplast
Green alga
ChloroplastRed alga
Heterotrophiceukaryotes
Secondaryendosymbiosis
Secondaryendosymbiosis
Nucleus
Primaryendosymbiosis
Cyanobacterium
Heterotrophiceukaryote
Evolved intochloroplast
Autotrophiceukaryotes
Nucleus
Nucleus
Chloroplast
Green alga
ChloroplastRed alga
Heterotrophiceukaryotes
Secondaryendosymbiosis
Secondaryendosymbiosis
Remnant ofgreen alga
Euglenozoans
Remnant ofred alga
Dinoflagellates
Apicomplexans
Stramenopiles
The taxonomy of protists remains a work in progress
– The names, boundaries, and placement of clades will continue to change as genomes of more protists are sequenced and compared
16.13 A tentative phylogeny of eukaryotes includes multiple clades of protists
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Diplomonads
Water molds
Parabasalids
Euglenozoans
Dinoflagellates
Apicomplexans
Ciliates
Brown algae
Diatoms
Forams
Radiolarians
Red algae
Chlorophytes
Charophytes
Land plants
Gre
en
alg
ae
Amoebas
Slime molds
Fungi
Choanoflagellates
Animals
Alv
eo
late
sA
mo
eb
ozo
an
sS
tram
en
op
iles
Diplomonads may be the most ancient surviving lineage of eukaryotes
– They have modified mitochondria without DNA or electron transport chains
– Most are anaerobic
Parabasalids are heterotrophic protists with modified mitochondria that generate some energy anaerobically
– The parasite Trichomonas vaginalis is sexually transmitted, feeding on white blood cells and bacteria living in the cells lining the vagina
16.14 Diplomonads and parabasalids have modified mitochondria
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Undulatingmembrane
Flagella
Euglenozoans are a diverse clade of protists
– Their common feature is a crystalline rod of unknown function inside their flagella
Euglenozoans include heterotrophs, photosynthetic autotrophs, and pathogenic parasites
16.15 Euglenozoans have flagella with a unique internal structure
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Video: Euglena Motion
Video: Euglena
Alveolates have membrane-enclosed sacs or alveoli beneath the plasma membrane
Dinoflagellates are important members of marine and freshwater phytoplankton
– Some live within coral animals, feeding coral reef communities
– Dinoflagellate blooms cause red tides
Ciliates use cilia to move and feed.
Apicomplexans are animal parasites such as Plasmodium, which causes malaria
16.16 Alveolates have sacs beneath the plasma membrane
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Copyright © 2009 Pearson Education, Inc.
16.16 Alveolates have sacs beneath the plasma membrane
Video: Dinoflagellate
Video: Paramecium Cilia
Video: Paramecium Vacuole
Video: Vorticella Cilia
Video: Vorticella Detail
Video: Vorticella Habitat
Macronucleus
Cilia
Stramenopiles are named for their “hairy” flagellum, usually paired with a “smooth” flagellum
– Water molds are fungus-like and decompose dead organisms in freshwater habitats
– Diatoms are unicellular, with silicate cell walls
– Brown algae are large, complex algae called seaweeds; all are multicellular and most are marine
16.17 Stramenopiles have “hairy” and smooth flagella
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Video: Water Mold Oogonium
Video: Water Mold Zoospores
Video: Diatoms Moving
Video: Various Diatoms
Amoebas move and feed by means of pseudopodia
Members of the clade amoebozoans include many free-living amoebas, some parasitic amoebas, and slime molds
– All have lobe-shaped pseudopodia
16.18 Amoebozoans have lobe-shaped pseudopodia
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Video: Plasmodial Slime Mold Streaming
Video: Plasmodial Slime Mold Zoom
Video: Amoeba
Video: Amoeba Pseudopodia
A plasmodial slime mold is an amoebozoan that forms a plasmodium, a multinucleate mass of cytoplasm
– The plasmodium extends pseudopodia through soil and rotting logs, engulfing food by phagocytosis as it grows
– Under adverse conditions, the plasmodium forms reproductive structures that produce spores
Cellular slime molds live as solitary amoeboid cells
– When food is scarce, the amoeboid cells swarm together, forming a slug-like aggregate that migrates, before forming a fruiting body borne on a stalk
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16.18 Amoebozoans have lobe-shaped pseudopodia
Foraminiferans and radiolarians move and feed by means of threadlike pseudopodia
Foraminiferans live in marine and freshwater
– They have porous tests composed of calcium carbonate, with small pores through which pseudopodia extend
Radiolarians produce an internal silicate skeleton
– The test is composed of organic materials
16.19 Foraminiferans and radiolarians have threadlike pseudopodia
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Red algae are typically soft-bodied, but some have cell walls encrusted with hard, chalky deposits
Green algae split into two groups, the chlorophytes and the charophytes
– The charophytes are the closest living relatives of land plants
16.20 Red algae and green algae are the closest relatives of land plants
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Copyright © 2009 Pearson Education, Inc.
16.20 Red algae and green algae are the closest relatives of land plants
Video: Chlamydomonas
Video: Volvox Colony
Video: Volvox Daughter
Video: Volvox Female Spheroid
Video: Volvox Falgella
Video: Volvox Inversion 1
Video: Volvox Sperm and Female
Video: Volvox Inversion 2
Volvoxcolonies
Chlamydomonas
The life cycles of most green algae involve the alternation of generations, in which a haploid (n) gametophyte alternates with a diploid (2n) sporophyte generation
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16.20 Red algae and green algae are the closest relatives of land plants
Femalegametophyte
Gametes
Key
Fusion ofgametes
Malegametophyte
Meiosis
Spores
Mitosis
SporophyteZygote
Mitosis
Mitosis
Haploid (n)
Diploid (2n)
Multicellularity evolved in several different lineages, probably by specialization of the cells of colonial protists.
– Stramenopile lineage brown algae
– Unnamed lineage red algae, green algae, land plants
– Opisthokont lineage fungi and animals
Multicellular life arose over a billion years ago.
By 543 million years ago, diverse animals and multicellular algae lived in aquatic environments; plants and fungi colonized land 500 million years ago
16.21 EVOLUTION CONNECTION:Multicellularity evolved several times in eukaryotes
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Unicellular
protist
Colony
1
Unicellular
protist
Colony
1
Locomotor
cells
Early multicellular organismwith specialized, interdepen-dent cells
Food-synthesizingcells
2
Unicellular
protist
Colony
1
Locomotor
cells
Early multicellular organismwith specialized, interdepen-dent cells
Food-synthesizingcells
2
Later organism thatproduces gametes
Somaticcells
Gamete
3
Chemoheterotroph
Photoheterotroph
Chemoautotroph
Photoautotroph
Nutritional Mode
Inorganic chemicals
Energy Source
Organic compounds
Sunlight
Sunlight
Carbon Source
Organic compounds
CO2
(a) (b)
(c)
(d)
1. Compare the characteristics of the three domains of life; explain why biologists consider Archaea to be more closely related to Eukarya than to Bacteria
2. Describe the structures and functions of the diverse features of prokaryotes; explain how these features have contributed to their success
3. Describe the nutritional diversity of prokaryotes; explain the significance of biofilms
4. Describe the diverse types of Archaea living in extreme and moderate environments
You should now be able to
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5. Distinguish between the subgroups of the domain Bacteria, noting the particular structure, special features, and habitats of each group
6. Distinguish between bacterial exotoxins and endotoxins, noting examples of each
7. Describe the positive natural roles of prokaryotes
8. Describe the basic types of protists; explain why biologists currently think that they represent many clades
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You should now be able to
9. Explain how primary endosymbiosis and secondary endosymbiosis led to further cellular diversity
10. Describe the major protist clades noting characteristics and examples of each
11. Describe the life cycle of Ulva, noting each form in the alternation of generations and how each is produced
12. Explain how multicellular life may have evolved in eukaryotes
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You should now be able to
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