Download PROKARYOTES

Figure 16.0_1
Chapter 16
Microbial Life: Prokaryotes and
Protists
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
Lecture by Edward J. Zalisko
© 2012 Pearson Education, Inc.
Figure 16.0_2
Figure 16.0_3
Chapter 16: Big Ideas
Prokaryotes
Protists
16.1 Prokaryotes are diverse and widespread
PROKARYOTES
 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 10
times that of all eukaryotes.
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© 2012 Pearson Education, Inc.
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Figure 16.1
16.1 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 or
beneficial.
© 2012 Pearson Education, Inc.
16.1 Prokaryotes are diverse and widespread
16.2 External features contribute to the success of
prokaryotes
 Several hundred species of bacteria live in and on
our bodies,
 Prokaryotic cells have three common cell shapes.
– decomposing dead skin cells,
– supplying essential vitamins, and
– Cocci are spherical prokaryotic cells. They sometimes
occur in chains that are called streptococci.
– Bacilli are rod-shaped prokaryotes. Bacilli may also be
threadlike, or filamentous.
– guarding against pathogenic organisms.
 Prokaryotes in soil decompose dead organisms,
sustaining chemical cycles.
– Spiral prokaryotes are like a corkscrew.
– Short and rigid prokaryotes are called spirilla.
– Longer, more flexible cells are called spirochetes.
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Figure 16.2A
Figure 16.2A_1
Cocci
Bacilli
Spirochete
Cocci
2
Figure 16.2A_2
Figure 16.2A_3
Spirochete
Bacilli
16.2 External features contribute to the success of
prokaryotes
Figure 16.2B
 Nearly all prokaryotes have a cell wall. Cell walls
– provide physical protection and
– prevent the cell from bursting in a hypotonic
environment.
 When stained with Gram stain, cell walls of
bacteria are either
– Gram-positive, with simpler cell walls containing
peptidoglycan, or
– Gram-negative, with less peptidoglycan, and more
complex and more likely to cause disease.
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16.2 External features contribute to the success of
prokaryotes
 The cell wall of many prokaryotes is covered by a
capsule, a sticky layer of polysaccharides or
protein.
Figure 16.2C
Tonsil cell
Capsule
 The capsule
– enables prokaryotes to adhere to their substrate or to
other individuals in a colony and
– shields pathogenic prokaryotes from attacks by a host’s
immune system.
Bacterium
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16.2 External features contribute to the success of
prokaryotes
Figure 16.2D
 Some prokaryotes have external structures that
extend beyond the cell wall.
Flagella
– Flagella help prokaryotes move in their environment.
– Hairlike projections called fimbriae enable prokaryotes
to stick to their substrate or each other.
Fimbriae
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16.3 Populations of prokaryotes can adapt rapidly
to changes in the environment
16.3 Populations of prokaryotes can adapt rapidly
to changes in the environment
 Prokaryote population growth
 The genome of a prokaryote typically
– has about one-thousandth as much DNA as a
eukaryotic genome and
– 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 population
will survive changes in the environment.
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– is one long, circular chromosome packed into a distinct
region of the cell.
 Many prokaryotes also have additional small,
circular DNA molecules called plasmids, which
replicate independently of the chromosome.
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Figure 16.3A
Chromosome
Plasmids
16.3 Populations of prokaryotes can adapt rapidly
to changes in the environment
 Some prokaryotes form specialized cells called
endospores that remain dormant through harsh
conditions.
 Endospores can survive extreme heat or cold.
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Figure 16.3B
16.4 Prokaryotes have unparalleled nutritional
diversity
 Prokaryotes exhibit much more nutritional diversity
than eukaryotes.
Endospore
 Two sources of energy are used.
– Phototrophs capture energy from sunlight.
– Chemotrophs harness the energy stored in chemicals.
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16.4 Prokaryotes have unparalleled nutritional
diversity
16.4 Prokaryotes have unparalleled nutritional
diversity
 Two sources of carbon are used by prokaryotes.
 The terms that describe how prokaryotes obtain
energy and carbon are combined to describe their
modes of nutrition.
– Autotrophs obtain carbon atoms from carbon dioxide.
– Heterotrophs obtain their carbon atoms from the
organic compounds present in other organisms.
– Photoautotrophs obtain energy from sunlight and use
carbon dioxide for carbon.
– Photoheterotrophs obtain energy from sunlight but get
their carbon atoms from organic molecules.
– Chemoautotrophs harvest energy from inorganic
chemicals and use carbon dioxide for carbon.
– Chemoheterotrophs acquire energy and carbon from
organic molecules.
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© 2012 Pearson Education, Inc.
Figure 16.4
Figure 16.4_1
ENERGY SOURCE
Chemicals
Chemoautotrophs
Photoautotrophs
CO2
Organic compounds
CARBON SOURCE
Sunlight
Photoautotrophs
Oscilliatoria
Unidentified “rock-eating” bacteria
Photoheterotrophs
Chemoheterotrophs
Oscilliatoria
Rhodopseudomonas
A Bdellovibrio attacking a
larger cell
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Figure 16.4_2
Figure 16.4_3
Photoheterotrophs
Chemoautotrophs
Unidentified “rock-eating” bacteria
Rhodopseudomonas
Figure 16.4_4
Chemoheterotrophs
16.5 CONNECTION: Biofilms are complex
associations of microbes
 Biofilms
– are complex associations of one or several species of
prokaryotes and
– may also include protists and fungi.
 Prokaryotes attach to surfaces and form biofilm
communities that
– are difficult to eradicate and
A Bdellovibrio attacking a larger cell
– may cause medical and environmental problems.
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16.5 CONNECTION: Biofilms are complex
associations of microbes
16.5 CONNECTION: Biofilms are complex
associations of microbes
 Biofilms are large and complex “cities” of microbes
that
 Biofilms that form in the environment can be
difficult to eradicate.
– communicate by chemical signals,
– coordinate a division of labor and defense against
invaders, and
– use channels to distribute nutrients and collect wastes.
 Biofilms
– clog and corrode pipes,
– gum up filters and drains, and
– Coat the hulls of ships.
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Figure 16.5
16.6 CONNECTION: Prokaryotes help clean up
the environment
 Prokaryotes are useful for cleaning up contaminants
in the environment because prokaryotes
– have great nutritional diversity,
– are quickly adaptable, and
– can form biofilms.
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16.6 CONNECTION: Prokaryotes help clean up
the environment
16.6 CONNECTION: Prokaryotes help clean up
the environment
 Bioremediation is the use of organisms to remove
pollutants from
 Prokaryotic decomposers are the mainstays of
sewage treatment facilities.
– soil,
– air, or
– water.
– Raw sewage is first passed through a series of screens
and shredders.
– Solid matter then settles out from the liquid waste,
forming sludge.
– Sludge is gradually added to a culture of anaerobic
prokaryotes, including bacteria and archaea.
– The microbes decompose the organic matter into material
that can be placed in a landfill or used as fertilizer.
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16.6 CONNECTION: Prokaryotes help clean up
the environment
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Figure 16.6A
 Liquid wastes are treated separately from the
sludge.
– Liquid wastes are sprayed onto a thick bed of rocks.
– Biofilms of aerobic bacteria and fungi growing on the
rocks remove much of the dissolved organic material.
Rotating
spray arm
– Fluid draining from the rocks is sterilized and then
released, usually into a river or ocean.
Rock bed coated
with aerobic
prokaryotes
and fungi
Liquid wastes
Outflow
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Figure 16.6A_1
Figure 16.6A_2
Rotating
spray arm
Rock bed coated
with aerobic
prokaryotes
and fungi
Rotating
spray arm
Liquid wastes
Outflow
16.6 CONNECTION: Prokaryotes help clean up
the environment
Rock bed coated with
aerobic prokaryotes
and fungi
Figure 16.6B
 Bioremediation is becoming an important tool for
cleaning up toxic chemicals released into the soil
and water by industrial processes.
 Environmental engineers change the natural
environment to accelerate the activity of naturally
occurring prokaryotes capable of metabolizing
pollutants.
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16.7 Bacteria and archaea are the two main
branches of prokaryotic evolution
Table 16.7
 New studies of representative genomes of
prokaryotes and eukaryotes strongly support the
three-domain view of life.
– Prokaryotes are now classified into two domains:
– Bacteria and
– Archaea.
– Archaea have at least as much in common with
eukaryotes as they do with bacteria.
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16.8 Archaea thrive in extreme environments—
and in other habitats
Figure 16.8A
 Archaeal inhabitants of extreme environments
have unusual proteins and other molecular
adaptations that enable them to metabolize and
reproduce effectively.
– Extreme halophiles thrive in very salty places.
– Extreme thermophiles thrive in
– very hot water, such as geysers, and
– acid pools.
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16.8 Archaea thrive in extreme environments—
and in other habitats
Figure 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.
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16.9 Bacteria include a diverse assemblage of
prokaryotes
 The domain Bacteria is currently divided into five
groups, based on comparisons of genetic
sequences.
 1. Proteobacteria
– are all gram negative,
– share a particular rRNA sequence, and
– represent all four modes of nutrition.
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16.9 Bacteria include a diverse assemblage of
prokaryotes
– Thiomargarita namibiensis is a type of proteobacteria
that
– is a giant among prokaryotes, typically ranging up to
100–300 microns in diameter,
– uses H2S to generate organic molecules from CO2,
and
– produces sulfur wastes, seen as small greenish
globules in the following figure.
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Figure 16.9A
16.9 Bacteria include a diverse assemblage of
prokaryotes
– Proteobacteria also include Rhizobium species that
– live symbiotically in root nodules of legumes and
– convert atmospheric nitrogen gas into a form usable
by their legume host.
– Symbiosis is a close association between
organisms of two or more species.
– Rhizobium is an endosymbiont, living within another
species.
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Figure 32.13B
16.9 Bacteria include a diverse assemblage of
prokaryotes
Shoot
 2. Gram-positive bacteria
– rival proteobacteria in diversity and
Bacteria within
vesicle in an
infected cell
Nodules
Roots
– include the actinomycetes common in soil.
– Streptomyces is often cultured by pharmaceutical
companies as a source of many antibiotics.
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Figure 16.9B
16.9 Bacteria include a diverse assemblage of
prokaryotes
 3. Cyanobacteria
– Cyanobacteria are the only group of prokaryotes with
plantlike, oxygen-generating photosynthesis.
– Some species, such as Anabaena, have specialized
cells that fix nitrogen.
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Figure 16.9C
16.9 Bacteria include a diverse assemblage of
prokaryotes
 4. Chlamydias
– Chlamydias live inside eukaryotic host cells.
Photosynthetic
cells
– Chlamydia trachomatis
Nitrogen-fixing
cells
– is a common cause of blindness in developing
countries and
– is the most common sexually transmitted disease in
the United States.
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Figure 16.9D
16.9 Bacteria include a diverse assemblage of
prokaryotes
 5. Spirochetes are
– helical bacteria and
– notorious pathogens, causing
– syphilis and
– Lyme disease.
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Figure 16.9E
16.10 CONNECTION: Some bacteria cause
disease
 All organisms are almost constantly exposed to
pathogenic bacteria.
 Most bacteria that cause illness do so by producing
a poison.
– Exotoxins are proteins that bacterial cells secrete into
their environment.
– Endotoxins are components of the outer membrane of
gram-negative bacteria.
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Figure 16.10
16.11 SCIENTIFIC DISCOVERY: Koch’s
postulates are used to prove that a
bacterium causes a disease
 Koch’s postulates are four essential conditions used
to establish that a certain bacterium is the cause of a
disease. They are
1. find the bacterium in every case of the disease,
2. isolate the bacterium from a person who has the disease
and grow it in pure culture,
3. show that the cultured bacterium causes the disease
when transferred to a healthy subject, and
4. isolate the bacterium from the experimentally infected
subject.
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16.11 SCIENTIFIC DISCOVERY: Koch’s
postulates are used to prove that a
bacterium causes a disease
Figure 16.11
 Koch’s postulates were used to demonstrate that
the bacterium Helicobacter pylori is the cause of
most peptic ulcers.
 The 2005 Nobel Prize in Medicine was awarded to
Barry Marshall and Robin Warren for this
discovery.
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16.12 CONNECTION: Bacteria can be used as
biological weapons
Figure 16.12
 Bacteria that cause anthrax and the plague can be
used as biological weapons.
– Bacillus anthracis killed five people in the United States
in 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.
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16.12 CONNECTION: Bacteria can be used as
biological weapons
 Clostridium botulinum produces the exotoxin
botulinum, the deadliest poison on earth.
PROTISTS
 Botulinum blocks transmission of nerve signals and
prevents muscle contraction.
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16.13 Protists are an extremely diverse assortment
of eukaryotes
16.13 Protists are an extremely diverse assortment
of eukaryotes
 Protists
 Protists obtain their nutrition in many ways. Protists
include
– are a diverse collection of mostly unicellular eukaryotes,
– may constitute multiple kingdoms within the Eukarya,
and
– autotrophs, called algae, producing their food by
photosynthesis,
– heterotrophs, called protozoans, eating bacteria and
other protists,
– refer to eukaryotes that are not
– plants,
– heterotrophs, called parasites, deriving their nutrition
from a living host, and
– animals, or
– fungi.
– mixotrophs, using photosynthesis and heterotrophy.
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© 2012 Pearson Education, Inc.
Figure 16.13A
Figure 16.13A_1
Autotrophy
Autotrophy
Caulerpa, a green alga
Heterotrophy
Giardia, a parasite
Mixotrophy
Euglena
Caulerpa, a green alga
13
Figure 16.13A_2
Figure 16.13A_3
Heterotrophy
Mixotrophy
Giardia, a parasite
16.13 Protists are an extremely diverse assortment
of eukaryotes
Euglena
Figure 16.13B
 Protists are found in many habitats including
– anywhere there is moisture and
– the bodies of host organisms.
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Figure 16.13B_1
Figure 16.13B_2
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16.13 Protists are an extremely diverse assortment
of eukaryotes
 Recent molecular and cellular studies indicate that
nutritional modes used to categorize protists do not
reflect natural clades.
16.14 EVOLUTION CONNECTION: Secondary
endosymbiosis is the key to much of protist
diversity
 The endosymbiont theory explains the origin of
mitochondria and chloroplasts.
 Protist phylogeny remains unclear.
– Eukaryotic cells evolved when prokaryotes established
residence within other, larger prokaryotes.
 One hypothesis, used here, proposes five
monophyletic supergroups.
– This theory is supported by present-day mitochondria and
chloroplasts that
– have structural and molecular similarities to
prokaryotic cells and
– replicate and use their own DNA, separate from the
nuclear DNA of the cell.
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Figure 16.14_s1
Figure 16.14_s2
Primary
endosymbiosis
Primary
endosymbiosis
Green alga
Chloroplast
Evolved into
Cyanobacterium chloroplast
Evolved into
Cyanobacterium chloroplast
2
2
3
Nucleus
Heterotrophic
eukaryote
Nucleus
Heterotrophic
eukaryote
1
1
Autotrophic
eukaryotes
Chloroplast
Red alga
Figure 16.14_s3
16.14 EVOLUTION CONNECTION: Secondary
endosymbiosis is the key to much of protist
diversity
Primary
endosymbiosis
 Secondary endosymbiosis is
Green alga
Chloroplast
Evolved into
Cyanobacterium chloroplast
– the process in which an autotrophic eukaryotic protist
became endosymbiotic in a heterotrophic eukaryotic
protist and
2
3
1
Nucleus
Heterotrophic
eukaryote
Autotrophic
eukaryotes
4
Heterotrophic
eukaryotes
– key to protist diversity.
Chloroplast
Red alga
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Figure 16.14_s4
Figure 16.14_s5
Primary
endosymbiosis
Secondary
endosymbiosis
Primary
endosymbiosis
Green alga
Secondary
endosymbiosis
Green alga
Chloroplast
Evolved into
Cyanobacterium chloroplast
Chloroplast
Evolved into
Cyanobacterium chloroplast
2
2
Remnant of
green alga
Euglena
3
1
Nucleus
Heterotrophic
eukaryote
Autotrophic
eukaryotes
4
Heterotrophic
eukaryotes
3
5
1
Nucleus
Heterotrophic
eukaryote
Chloroplast
Autotrophic
eukaryotes
4
Heterotrophic
eukaryotes
5
Chloroplast
Red alga
16.15 Chromalveolates represent the range of
protist diversity
Red alga
Figure 16.15A
 Chromalveolates include
– diatoms, unicellular algae with a glass cell wall
containing silica,
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16.15 Chromalveolates represent the range of
protist diversity
Figure 16.15B
 Chromalveolates include
– diatoms, unicellular algae with a glass cell wall
containing silica,
– dinoflagellates, unicellular autotrophs, heterotrophs,
and mixotrophs that are common components of marine
plankton,
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16.15 Chromalveolates represent the range of
protist diversity
Figure 16.15C
 Chromalveolates include
– diatoms, unicellular algae with a glass cell wall
containing silica,
– dinoflagellates, unicellular autotrophs, heterotrophs,
and mixotrophs that are common components of marine
plankton,
– brown algae, large, multicellular autotrophs,
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16.15 Chromalveolates represent the range of
protist diversity
Figure 16.15D
 Chromalveolates include
– diatoms, unicellular algae with a glass cell wall
containing silica,
– dinoflagellates, unicellular autotrophs, heterotrophs,
and mixotrophs that are common components of marine
plankton,
– brown algae, large, multicellular autotrophs,
– water molds, unicellular heterotrophs,
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16.15 Chromalveolates represent the range of
protist diversity
Figure 16.15E
 Chromalveolates include
– diatoms, unicellular algae with a glass cell wall
containing silica,
Mouth
– dinoflagellates, unicellular autotrophs, heterotrophs,
and mixotrophs that are common components of marine
plankton,
– brown algae, large, multicellular autotrophs,
– water molds, unicellular heterotrophs,
– ciliates, unicellular heterotrophs and mixotrophs that
use cilia to move and feed,
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16.15 Chromalveolates represent the range of
protist diversity
16.16 CONNECTION: Can algae provide a
renewable source of energy?
 Chromalveolates include
 Fossil fuels
– diatoms, unicellular algae with a glass cell wall
containing silica,
– are the organic remains of organisms that lived
hundreds of millions of years ago and
– dinoflagellates, unicellular autotrophs, heterotrophs,
and mixotrophs that are common components of marine
plankton,
– primarily consist of
– diatoms and
– brown algae, large, multicellular autotrophs,
– primitive plants.
– water molds, unicellular heterotrophs,
– ciliates, unicellular heterotrophs and mixotrophs that use
cilia to move and feed, and
– a group including parasites, such as Plasmodium, which
causes malaria.
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16.16 CONNECTION: Can algae provide a
renewable source of energy?
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Figure 16.16
 Lipid droplets in diatoms and other algae may
serve as a renewable source of energy.
 If unicellular algae could be grown on a large scale,
this oil could be harvested and processed into
biodiesel.
 Numerous technical hurdles remain before
industrial-scale production of biofuel from algae
becomes a reality.
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16.17 Rhizarians include a variety of amoebas
16.17 Rhizarians include a variety of amoebas
 The two largest groups of Rhizaria are among the
organisms referred to as amoebas.
 Foraminiferans
 Amoebas move and feed by means of
pseudopodia, temporary extensions of the cell.
– are found in the oceans and in fresh water,
– have porous shells, called tests, composed of calcium
carbonate, and
– have pseudopodia that function in feeding and
locomotion.
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© 2012 Pearson Education, Inc.
18
Figure 16.17A
Figure 16.17A_2
Figure 16.17A_1
16.17 Rhizarians include a variety of amoebas
 Radiolarians
– are mostly marine and
– produce a mineralized internal skeleton made of silica.
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Figure 16.17B
16.18 Some excavates have modified mitochondria
 Excavata has recently been proposed as a clade
on the basis of molecular and morphological
similarities.
 The name refers to an “excavated” feeding groove
possessed by some members of the group.
 Excavates
– have modified mitochondria that lack functional electron
transport chains and
– use anaerobic pathways such as glycolysis to extract
energy.
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19
16.18 Some excavates have modified mitochondria
Figure 16.13B
 Excavates include
– heterotrophic termite endosymbionts
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16.18 Some excavates have modified mitochondria
Figure 16.13A_3
Mixotrophy
 Excavates include
– heterotrophic termite endosymbionts,
– autotrophic species,
– mixotrophs such as Euglena
Euglena
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16.18 Some excavates have modified mitochondria
 Excavates include
Figure 16.13A
Autotrophy
Heterotrophy
Mixotrophy
– heterotrophic termite endosymbionts,
– autotrophic species,
– mixotrophs such as Euglena,
– the common waterborne parasite Giardia intestinalis,
Caulerpa, a green alga
Giardia, a parasite
Euglena
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20
16.18 Some excavates have modified mitochondria
Figure 16.18A
 Excavates include
Flagella
– heterotrophic termite endosymbionts,
– autotrophic species,
– mixotrophs such as Euglena,
– the common waterborne parasite Giardia intestinalis,
Undulating
membrane
– the parasite Trichomonas vaginalis, which causes 5
million new infections each year of human reproductive
tracts,
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16.18 Some excavates have modified mitochondria
Figure 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 5
million new infections each year of human reproductive
tracts, and
– the parasite Trypanosoma, which causes sleeping
sickness in humans.
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16.19 Unikonts include protists that are closely
related to fungi and animals
16.19 Unikonts include protists that are closely
related to fungi and animals
 Unikonta is a controversial grouping joining
 Amoebozoans have lobe-shaped pseudopodia and
include
– amoebozoans and
– a group that includes animals and fungi, addressed at
the end of this unit on protists.
– many species of free-living amoebas,
– some parasitic amoebas, and
– slime molds.
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21
Figure 16.19A
16.19 Unikonts include protists that are closely
related to fungi and animals
 Plasmodial slime molds
– are common where there is moist, decaying organic
matter and
– consist of a single, multinucleate mass of cytoplasm
undivided by plasma membranes, called a
plasmodium.
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Figure 16.19B
Figure 16.19B_2
Figure 16.19B_1
16.19 Unikonts include protists that are closely
related to fungi and animals
 Cellular slime molds
– are common on rotting logs and decaying organic
matter and
– usually exist as solitary amoeboid cells, but when food
is scarce, amoeboid cells
– swarm together, forming a slug-like aggregate that
wanders around for a short time and then
– forms a stock supporting an asexual reproductive
structure that produces spores.
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22
Figure 16.19C
16.20 Archaeplastids include red algae, green
algae, and land plants
 Archaeplastids include:
– red algae,
– green algae, and
– land plants.
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16.20 Archaeplastids include red algae, green
algae, and land plants
Figure 16.20A
 Red algae
– are mostly multicellular,
– contribute to the structure of coral reefs, and
– are commercially valuable.
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16.20 Archaeplastids include red algae, green
algae, and land plants
Figure 16.20B
 Green algae may be unicellular, colonial, or
multicellular.
– Volvox is a colonial green algae, and
– Chlamydomonas is a unicellular alga propelled by two
flagella.
Volvox
Chlamydomonas
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23
Figure 16.20B_1
Figure 16.20B_2
Volvox
Chlamydomonas
16.20 Archaeplastids include red algae, green
algae, and land plants
Figure 16.20C_s1
Mitosis
Male
gametophyte
 Ulva, or sea lettuce, is
Spores
Mitosis
– a multicellular green alga with
Gametes
Female
gametophyte
– a complex life cycle that includes an alternation of
generations that consists of
– a multicellular diploid (2n) form, the sporophyte,
that alternates with
– a multicellular haploid (1n) form, the gametophyte.
Key
Haploid (n)
Diploid (2n)
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Figure 16.20C_s2
Figure 16.20C_s3
Mitosis
Mitosis
Male
gametophyte
Male
gametophyte
Spores
Mitosis
Spores
Mitosis
Gametes
Female
gametophyte
Meiosis
Gametes
Female
gametophyte
Fusion of
gametes
Fusion of
gametes
Sporophyte
Zygote
Zygote
Key
Haploid (n)
Diploid (2n)
Mitosis
Key
Haploid (n)
Diploid (2n)
24
Figure 16.20C_2
16.21 EVOLUTION CONNECTION: Multicellularity
evolved several times in eukaryotes
 The origin of the eukaryotic cell led to an
evolutionary radiation of new forms of life.
 Unicellular protists are much more diverse in form
than simpler prokaryotes.
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16.21 EVOLUTION CONNECTION: Multicellularity
evolved several times in eukaryotes
16.21 EVOLUTION CONNECTION: Multicellularity
evolved several times in eukaryotes
 Multicellular organisms (seaweeds, plants,
animals, and most fungi) are fundamentally
different from unicellular organisms.
 Multicellular organisms have evolved from three
different lineages:
– A multicellular organism has various specialized cells
that perform different functions and are interdependent.
– All of life’s activities occur within a single cell in
unicellular organisms.
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– brown algae evolved from chromalveolates,
– fungi and animals evolved from unikonts, and
– red algae and green algae evolved from achaeplastids.
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Figure 16.21A
Green algae
Other green algae
Charophytes
Land plants
Amoebozoans
Unikonts
Ancestral eukaryote
Archaeplastids
Red algae
Nucleariids
16.21 EVOLUTION CONNECTION: Multicellularity
evolved several times in eukaryotes
 One hypothesis states that two separate unikont
lineages led to fungi and animals, diverging more
than 1 billion years ago.
 A combination of morphological and molecular
evidence suggests that choanoflagellates are the
closest living protist relative of animals.
Fungi
Choanoflagellates
Key
All unicellular
Both unicellular
and multicellular
All multicellular
Animals
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25
Figure 16.21B
Figure 16.21B_1
Nucleariids
Fungi
A nucleariid, closest living
protistan relative of fungi
1 billion
years ago
Nucleariids
Individual
choanoflagellate
Choanoflagellates
Colonial
choanoflagellate
Fungi
A nucleariid, closest living
protistan relative of fungi
Sponge
collar cell
Animals
Sponge
Figure 16.21B_2
Figure 16.21B_3
Individual
choanoflagellate
Choanoflagellates
Colonial
choanoflagellate
Sponge
collar cell
Animals
Sponge
You should now be able to
You should now be able to
1. Describe the structures and functions of the diverse
features of prokaryotes; explain how these features have
contributed to their success.
6.
Describe the diverse types of Archaea living in extreme
and moderate environments.
7.
Distinguish between the subgroups of the domain
Bacteria, noting the particular structure, special features,
and habitats of each group.
3. Describe the nutritional diversity of prokaryotes and explain
the significance of biofilms.
8.
Distinguish between bacterial exotoxins and endotoxins,
noting examples of each.
4. Explain how prokaryotes help clean up the environment.
9.
5. Compare the characteristics of the three domains of life;
explain why biologists consider Archaea to be more closely
related to Eukarya than to Bacteria.
Describe the steps of Koch’s postulates and explain why
they are used.
10. Explain how bacteria can be used as biological weapons.
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2. Explain how populations of prokaryotes can adapt rapidly
to changes in their environment.
26
You should now be able to
Figure 16.UN01
11. Describe the extremely diverse assortment of eukaryotes.
12. Explain how primary endosymbiosis and secondary
endosymbiosis led to further cellular diversity.
Nutritional mode
Energy source
13. Describe the major protist clades noting characteristics
and examples of each.
Photoautotroph
Sunlight
Chemoautotroph
Inorganic chemicals
Photoheterotroph
Sunlight
14. Describe the life cycle of Ulva, noting each form in the
alternation of generations and how each is produced.
Chemoheterotroph
Organic compounds
Carbon source
CO2
Organic compounds
15. Explain how multicellular life may have evolved in
eukaryotes.
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Figure 16.UN02
Figure 16.UN02_1
Exotoxin
Secreted by cell
Endotoxin
Component of gramnegative plasma membrane
Staphylococcus aureus
Salmonella enteritidis
Figure 16.UN02_2
Exotoxin
Secreted by cell
Staphylococcus aureus
Figure 16.UN03
(a)
Red algae
Green
algae
Other green algae
(b)
Land plants
(c)
Salmonella enteritidis
Ancestral eukaryote
Endotoxin
Component of gramnegative plasma membrane
Amoebozoans
Nucleariids
(d)
(e)
(f)
27