Chapter 15 1 Chapter 15 Outline: The Evolution of...
Transcript of Chapter 15 1 Chapter 15 Outline: The Evolution of...
© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko
PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Chapter 15Chapter 15The Evolution of Microbial Life
1
• Major Episodes in the History of Life
• The Origin of Life
• Prokaryotes
• Protists
Chapter 15 Outline: The Evolution of Microbial Life
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Biology and Society: Has Life Been Created in the Lab?
• How did life first arise on Earth?
• To gain insight, scientists have
– synthesized from scratch the entire genome of a small bacterium known as Mycoplasma mycoides
and
– transplanted the artificial genome into the cells of a closely related species called Mycoplasma
capricolum.
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• The newly installed genome
– took over the recipient cells,
– began cranking out M. mycoides proteins, and
– reproduced to make more cells containing the synthetic M. mycoides genome.
Biology and Society: Has Life Been Created in the Lab?
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• Major Episodes in the History of Life
• The Origin of Life
• Prokaryotes
• Protists
Chapter 15 Outline: The Evolution of Microbial Life
© 2013 Pearson Education, Inc.
5 MAJOR EPISODES IN THE HISTORY OF LIFE
• Earth was formed about 4.6 billion years ago.
• Prokaryotes
– evolved by about 3.5 billion years ago,
– began oxygen production about 2.7 billion years ago
– Many killed off because oxygen byproducts can
be very toxic
– lived alone for more than a billion years, and
– continue in great abundance today.
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• Single-celled eukaryotes first evolved about 2.1
billion years ago.
• Multicellular eukaryotes first evolved at least 1.2
billion years ago.
MAJOR EPISODES IN THE HISTORY OF LIFE
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7 Figure 15.1a
Precambrian
Ancestor to
all present-day life
Origin of
EarthEarth’s crust
solidifies
Oldest prokaryotic fossils
Atmospheric oxygen begins to appear
Millions of years ago
4,500 4,000 3,500 3,000 2,500
8
Figure 15.1b
Millions of years ago
2,000 1,500 1,000
Precambrian
Oldest eukaryoticfossils
Origin ofmulticellularorganisms
Oldestanimalfossils
9 Figure 15.1c
Millions of years ago
1,000 500 0
Precambrian Paleozoic CenozoicMeso-zoic
Bacteria
Archaea
Plants
Fungi
AnimalsCambrian explosion
Oldest animalfossils
Plantscolonize land
Extinction ofdinosaurs
First humans
Pro
tists
Pro
ka
ryo
tes
Eu
ka
ryo
tes
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• All the major phyla of animals evolved by the end
of the Cambrian explosion, which
– began about 540 million years ago and
– lasted about 10 million years.
• Plants and fungi
– first colonized land about 500 million years ago and
– were followed by amphibians that evolved from fish.
MAJOR EPISODES IN THE HISTORY OF LIFE
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• What if we use a clock analogy to tick down all of
the major events in the history of life on Earth?
MAJOR EPISODES IN THE HISTORY OF LIFE
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Figure 15.2
Humans
Origin of solarsystem and Earth
1 4
2 3
0
13
• Major Episodes in the History of Life
• The Origin of Life
• Resolving the Biogenesis Paradox
• A Four-Stage Hypothesis for the Origin of Life
• From Chemical Evolution to Darwinian Evolution
• Prokaryotes
• Protists
Chapter 15 Outline: The Evolution of Microbial Life
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THE ORIGIN OF LIFE
• We may never know for sure how life on Earth
began.
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15 Resolving the Biogenesis Paradox
• All life today arises by the reproduction of
preexisting life, or biogenesis.
• If this is true, how could the first organisms arise?
• From the time of the ancient Greeks until well into
the 1800s, it was commonly believed that life
regularly arises from nonliving matter, an idea
called spontaneous generation.
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• Today, most biologists think it is possible that life
on early Earth evolved from simple cells produced
by
– chemical and
– physical processes.
Resolving the Biogenesis Paradox
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17 A Four-Stage Hypothesis for the Origin of Life
• According to one hypothesis, the first organisms
were products of chemical evolution in four
stages.
1. The abiotic synthesis of small organic molecules
2. The joining of these molecules into macromolecules
3. The packaging of these molecules into pre-cells
4. The origin of self-replicating molecules that made inheritance possible
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Figure 15.UN04
Inorganic compounds
Abiotic synthesisof organic monomers
Abiotic synthesisof polymers
Formation of pre-cells
Self-replicatingmolecules
Membrane-enclosed compartment
Complementarychain
Polymer
Organic monomers
2
1
3
4
19 Stage 1: Abiotic Synthesis of Organic Monomers
• The first stage in the origin of life was the first to
be extensively studied in the laboratory.
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The Process of Science:Can Biological Monomers Form Spontaneously?
• Observation: Modern biological macromolecules
are all composed of elements that were present in
abundance on early Earth.
• Question: Could biological molecules arise
spontaneously under conditions like those on
early Earth?
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• Hypothesis: A closed system designed to simulate
early Earth conditions could produce biologically
important organic molecules from inorganic
ingredients.
• Prediction: Organic molecules would form and
accumulate.
The Process of Science:Can Biological Monomers Form Spontaneously?
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• Experiment: An apparatus was built to mimic the
early Earth atmosphere and included
– hydrogen gas (H2), methane (CH4), ammonia (NH3), and water vapor (H2O),
– sparks that were discharged into the chamber to mimic the prevalent lightning of early Earth, and
– a condenser that cooled the atmosphere, causing water and dissolved compounds to “rain” into the miniature “sea.”
The Process of Science:Can Biological Monomers Form Spontaneously?
© 2013 Pearson Education, Inc.
23 Figure 15.4
Miller and Urey’s experiment
“Sea”
H2O
Sample for
chemical analysis
Cooled water
containing organic
molecules
Cold water
Condenser
Electrode
“Atmosphere”
Water vapor
CH4
NH3 H2
24
• Results: After the apparatus had run for a week,
an abundance of organic molecules essential for
life had collected in the “sea,” including amino
acids, the monomers of proteins.
• These laboratory experiments
– have been repeated and extended by other scientists and
– support the idea that organic molecules could have arisen abiotically on early Earth.
The Process of Science:Can Biological Monomers Form Spontaneously?
© 2013 Pearson Education, Inc.
25 Stage 2: Abiotic Synthesis of Polymers
• Researchers have brought about the
polymerization of monomers to form polymers,
such as proteins and nucleic acids, by dripping
solutions of organic monomers onto
– hot sand,
– clay, or
– rock.
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Stage 3: Formation of Pre-Cells
• A key step in the origin of life was the isolation of a
collection of abiotically created molecules within a
membrane.
• Laboratory experiments demonstrate that pre-cells
could have formed spontaneously from abiotically
produced organic compounds.
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• Such pre-cells produced in the laboratory display
some lifelike properties. They
– have a selectively permeable surface,
– can grow by absorbing molecules from their surroundings, and
– swell or shrink when placed in solutions of different salt concentrations.
Stage 3: Formation of Pre-Cells
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Stage 4: Origin of Self-Replicating Molecules
• Life is defined partly by the process of inheritance,
which is based on self-replicating molecules.
• One hypothesis is that the first genes were short
strands of RNA that replicated themselves
– without the assistance of proteins,
– perhaps using RNAs that can act as enzymes, called ribozymes.
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29 Figure 15.5-1
RNAmonomers
30
Figure 15.5-2
RNAmonomers
Formation ofshort RNApolymers:simple “genes”
31 Figure 15.5-3
RNAmonomers
Formation ofshort RNApolymers:simple “genes”
Assembly of acomplementaryRNA chain
32
Figure 15.5-4
Original“gene”
RNAmonomers
Formation ofshort RNApolymers:simple “genes”
Assembly of acomplementaryRNA chain
Thecomplementarychain serves asa template of theoriginal “gene.”
33 Figure 15.UN04
Inorganic compounds
Abiotic synthesisof organic monomers
Abiotic synthesisof polymers
Formation of pre-cells
Self-replicatingmolecules
Membrane-enclosed compartment
Complementarychain
Polymer
Organic monomers
2
1
3
4
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From Chemical Evolution to Darwinian Evolution
• Over millions of years
– natural selection favored the most efficient pre-cells and
…yada yada yada…
– the first prokaryotic cells evolved!
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• Major Episodes in the History of Life
• The Origin of Life
• Prokaryotes
• They’re Everywhere!
• The Structure and Function of Prokaryotes
• The Two Main Branches of Prokaryotic Evolution: Bacteria
and Archaea
• Bacteria and Disease
• The Ecological Impact of Prokaryotes
• Protists
Chapter 15 Outline: The Evolution of Microbial Life
© 2013 Pearson Education, Inc.
36
PROKARYOTES
• Prokaryotes lived and evolved all alone
on Earth for about 2 billion years.
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37 They’re Everywhere!
• Prokaryotes
– are found wherever there is life,
– have a collective biomass that is at least ten times that of all eukaryotes,
– thrive in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote,
– cause about half of all human diseases, and
– are more commonly benign or beneficial.
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• Compared to eukaryotes, prokaryotes are
– much more abundant and
– typically much smaller.
They’re Everywhere!
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39 Figure 15.7
Co
lori
zed
SE
M 40
• Prokaryotes living in soil and at the bottom of
lakes, rivers, and oceans help to decompose
dead organisms and other organic waste
material, returning vital chemical elements to
the environment.
They’re Everywhere!
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41 The Structure and Function of Prokaryotes
• Prokaryotic cells
– lack a membrane-enclosed nucleus,
– lack other membrane-enclosed organelles,
– typically have cell walls exterior to their plasma membranes, but
– display an enormous range of diversity.
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Figure 4.4
Plasma membrane
Cell wall
Capsule
Prokaryoticflagellum
Ribosomes
Nucleoid
Pili
Co
lori
zed
TE
M
43 Figure 4.5
CytoskeletonRibosomes Centriole
Lysosome
Nucleus
Plasmamembrane
Mitochondrion
Rough endoplasmicreticulum (ER)
Golgi apparatus
Smoothendoplasmicreticulum (ER)
Idealized animal cell
Idealized plant cell
Cytoskeleton
Mitochondrion
Nucleus
Rough endoplasmicreticulum (ER)
Ribosomes
Smoothendoplasmic
reticulum (ER)
Golgi apparatus
Plasmamembrane
Channels between cells
Not in mostplant cells
Central vacuole
Cell wallChloroplast
Not in animal cells
44
PROTISTS
• Protists are
– eukaryotes that are not fungi, animals, or plants,
– mostly unicellular, and
– ancestral to all other eukaryotes.
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80 The Origin of Eukaryotic Cells
• Eukaryotic cells evolved by
– the infolding of the plasma membrane of a prokaryotic cell to form the endomembrane system and
– a process known as endosymbiosis.
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The Origin of Eukaryotic Cells
• Symbiosis is a more general association between
organisms of two or more species.
• Endosymbiosis
– refers to one species living inside another host species and
– is the process by which eukaryotes gained mitochondria and chloroplasts.
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82 Figure 15.19a
(a) Origin of the endomembrane system
Plasma membrane
DNA
Cytoplasm
Endoplasmicreticulum
Nucleus
Nuclearenvelope
Ancestralprokaryote
Membraneinfolding
Cell with nucleus andendomembrane system
83
Figure 15.19b
(b) Origin of mitochondria and chloroplasts
Photosyntheticeukaryotic cell
Photosyntheticprokaryote
Aerobicheterotrophicprokaryote
Endosymbiosis
Mitochondrion
Chloroplast
84 The Diversity of Protists
• The group called protists
– consists of multiple clades but
– remains a convenient term to refer to eukaryotes that are not plants, animals, or fungi.
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• Protists obtain their nutrition in a variety of ways.
– Algae are autotrophs, producing their food by photosynthesis.
The Diversity of Protists
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86 Evolution Connection: The Origin of Multicellular Life
• Multicellular organisms have
– specialized cells that are dependent on each other and perform different functions, such as
– feeding,
– waste disposal,
– gas exchange, and
– protection.
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• Colonial protists likely formed the evolutionary
links between
– unicellular and
– multicellular organisms.
• The colonial green alga Volvox demonstrates one
level of specialization and cooperation.
Evolution Connection: The Origin of Multicellular Life
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115 Figure 15.27-1
Unicellularprotist
An ancestralcolony may haveformed when acell divided andremainedattached toits offspring.
116
Figure 15.27-2
Unicellularprotist
Locomotorcells
Food-synthesizingcells
Cells in thecolony mayhave becomespecialized andinterdependent.
An ancestralcolony may haveformed when acell divided andremainedattached toits offspring.
117 Figure 15.27-3
Unicellularprotist
Locomotorcells
Food-synthesizingcells Somatic
cells
Gamete
Additionalspecialization mayhave led to sex cells(gametes) andnonreproductivecells (somatic cells).
Cells in thecolony mayhave becomespecialized andinterdependent.
An ancestralcolony may haveformed when acell divided andremainedattached toits offspring.
118