Chapter 15 The Evolution of Microbial Life Laura Coronado Bio 10
Chapter 15 Slide 2 Biology and Society: Can Life Be Created in the
Lab? A research group led by Craig Venter Synthesized the entire
genome of Mycoplasma genitalium, a species of bacteria found
naturally in the human urinary tract Transplanted the complete
genome of one species of Mycoplasma bacteria into another Hopes to
c reate an artificial genome & transplant it into a genome-free
host cell An artificial organism that could be completely
controlled might Clean up toxic wastes Generate biofuels Be unable
to survive outside rigidly controlled conditions Laura Coronado Bio
10 Chapter 15 Slide 3 MAJOR EPISODES IN THE HISTORY OF LIFE Earth
was formed about 4.6 billion years ago. Prokaryotes Evolved by 3.5
billion years ago Began oxygen production about 2.7 billion years
ago Lived alone for almost 2 billion years Continue in great
abundance today Single-celled eukaryotes first evolved about 2.1
billion years ago. Multicellular eukaryotes first evolved at least
1.2 billion years ago. Laura Coronado Bio 10 Chapter 15 Slide 4
Precambrian Common ancestor to all present-day life Origin of Earth
Earth cool enough for crust to solidify Oldest prokaryotic fossils
Atmospheric oxygen begins to appear due to photosynthetic
prokaryotes Millions of years ago 4,5004,0003,5003,0002,500 Figure
15.1a Laura Coronado Bio 10 Chapter 15 Slide 5
PaleozoicMesozoicCenozoic Bacteria Archaea Plants Fungi Animals
Prokaryotes Eukaryotes Protists Oldest eukaryotic fossils Origin of
multicellular organisms Oldest animal fossils Plants and symbiotic
fungi colonize land Extinction of dinosaurs First humans Millions
of years ago Cambrian explosion 2,0001,5001,0005000 Figure 15.1b
Laura Coronado Bio 10 Chapter 15 Slide 6 Major episodeMillions of
years ago All major animal phyla established Plants and fungi
colonize land Origin of Earth First multicellular organisms Oldest
eukaryotic fossils Accumulation of O 2 in atmosphere Oldest
prokaryotic fossils 500 530 1,200 1,800 2,400 3,500 4,600 Figure
15.UN03 Laura Coronado Bio 10 Chapter 15 Slide 7 MAJOR EPISODES IN
THE HISTORY OF LIFE 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 Were followed by amphibians
that evolved from fish What if we use a clock analogy to tick down
all of the major events in the history of life on Earth? Laura
Coronado Bio 10 Chapter 15 Slide 8 Humans Origin of solar system
and Earth 1 4 0 23 Pre sent Animals Coloniz of land ation Multi
eukar cellular yotes Sing eukar cel yotes le- led Atmo oxy sphe ric
gen Bil ars ons of ago ye li kary otes Pro Figure 15.2 Laura
Coronado Bio 10 Chapter 15 Slide 9 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 19 th
century, it was commonly believed that life regularly arises from
nonliving matter, an idea called spontaneous generation. Today,
most biologists think it is possible that life on early Earth
produced simple cells by chemical and physical processes. Laura
Coronado Bio 10 Chapter 15 Slide 10 Figure 15.3 Laura Coronado Bio
10 Chapter 15 Slide 11 A Four-Stage Hypothesis for the Origin of
Life According to one hypothesis, the first organisms were products
of chemical evolution in four stages. Stage 1: Abiotic Synthesis of
Organic Monomers The first stage in the origin of life has been the
most extensively studied by scientists in the laboratory. Laura
Coronado Bio 10 Chapter 15 Slide 12 The Process of Science: Can
Biological Monomers Form Spontaneously? Observation: Modern
biological macromolecules are all composed of elements that were
present in abundance on the early Earth. Question: Could biological
molecules arise spontaneously under conditions like those on the
early Earth? Hypothesis: A closed system designed in the laboratory
to simulate early Earth conditions could produce biologically
important organic molecules from inorganic ingredients. Prediction:
Organic molecules would form and accumulate. Laura Coronado Bio 10
Chapter 15 Slide 13 The Process of Science: Can Biological Monomers
Form Spontaneously? Experiment: An apparatus was built to mimic the
early Earth atmosphere and included Hydrogen gas (H 2 ), methane
(CH 4 ), ammonia (NH 3 ), and water vapor (H 2 O) Sparks were
discharged into the chamber to mimic the prevalent lightning of the
early Earth A condenser to cool the atmosphere, causing water and
dissolved compounds to rain into the miniature sea Laura Coronado
Bio 10 Chapter 15 Slide 14 Stanley Miller re-creating his 1953
experiment Miller and Ureys experiment Sea H2OH2O Sample for
chemical analysis Cooled water containing organic molecules Cold
water Condenser Electrode Atmosphere Water vapor CH 4 NH 3 H2H2
Figure 15.4 Laura Coronado Bio 10 Chapter 15 Slide 15 The Process
of Science: Can Biological Monomers Form Spontaneously? 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. Since Miller and Ureys
experiments, laboratory analogues of the primeval Earth have
produced All 20 amino acids Several sugars Laura Coronado Bio 10
Chapter 15 Slide 16 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 Rock Laura
Coronado Bio 10 Chapter 15 Slide 17 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. 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 Swell or shrink when
placed in solutions of different salt concentrations Laura Coronado
Bio 10 Chapter 15 Slide 18 Inorganic compounds Abiotic synthesis of
organic monomers Abiotic synthesis of polymers Formation of
pre-cells Self-replicating molecules Membrane-enclosed compartment
Complementary chain Polymer Organic monomers Figure 15.UN04 Laura
Coronado Bio 10 Chapter 15 Slide 19 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. Laura
Coronado Bio 10 Chapter 15 Slide 20 Original gene Complementary RNA
chain Figure 15.5 Laura Coronado Bio 10 Chapter 15 Slide 21 From
Chemical Evolution to Darwinian Evolution Over millions of years
Natural selection favored the most efficient pre-cells The first
prokaryotic cells evolved Prokaryotes lived and evolved all alone
on Earth for 2 billion years before eukaryotes evolved. Are found
wherever there is life Far outnumber eukaryotes Can cause disease
Can be beneficial Prokaryotes live deep within the Earth and in
habitats too cold, too hot, too salty, too acidic, or too alkaline
for any eukaryote to survive. Laura Coronado Bio 10 Chapter 15
Slide 22 Figure 15.6 Laura Coronado Bio 10 Chapter 15 Slide 23
Prokaryotes Compared to eukaryotes, prokaryotes are Much more
abundant Typically much smaller Prokaryotes Are ecologically
significant, recycling carbon and other vital chemical elements
back and forth between organic matter, the soil, and atmosphere
Cause about half of all human diseases Are more typically benign or
beneficial Laura Coronado Bio 10 Chapter 15 Slide 24 Colorized SEM
Figure 15.7 Laura Coronado Bio 10 Chapter 15 Slide 25 The Structure
and Function of Prokaryotes Prokaryotic cells Lack true nuclei Lack
other membrane-enclosed organelles Have cell walls exterior to
their plasma membranes Prokaryotes come in several shapes:
Spherical (cocci) Rod-shaped (bacilli) Spiral Most prokaryotes are
unicellular & very small Laura Coronado Bio 10 Chapter 15 Slide
26 Plasma membrane (encloses cytoplasm) Cell wall (provides
Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for
propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA)
Pili (attachment structures) Colorized TEM Figure 4.4 Laura
Coronado Bio 10 Chapter 15 Slide 27 Cytoskeleton RibosomesCentriole
Lysosome Flagellum Nucleus Plasma membrane Mitochondrion Rough
endoplasmic reticulum (ER) Golgi apparatus Smooth endoplasmic
reticulum (ER) Idealized animal cell Idealized plant cell
Cytoskeleton Mitochondrion Nucleus Rough endoplasmic reticulum (ER)
Ribosomes Smooth endoplasmic reticulum (ER) Golgi apparatus Plasma
membrane Channels between cells Not in most plant cells Central
vacuole Cell wall Chloroplast Not in animal cells Figure 4.5 Laura
Coronado Bio 10 Chapter 15 Slide 28 SHAPES OF PROKARYOTIC CELLS
Spherical (cocci)Rod-shaped (bacilli)Spiral Colorized SEM Colorized
TEM Figure 15.8 Laura Coronado Bio 10 Chapter 15 Slide 29 (a)
Actinomycete(b) Cyanobacteria(c) Giant bacterium Colorized SEM LM
Figure 15.9 Laura Coronado Bio 10 Chapter 15 Slide 30 The Structure
and Function of Prokaryotes Some prokaryotes Form true colonies
Show specialization of cells Are very large About half of all
prokaryotes are mobile, using flagella. Many have one or more
flagella that propel the cells away from unfavorable places or
toward more favorable places, such as nutrient-rich locales. Laura
Coronado Bio 10 Chapter 15 Slide 31 Plasma membrane Cell wall
Rotary movement of each flagellum Flagellum Colorized TEM Figure
15.10 Laura Coronado Bio 10 Chapter 15 Slide 32 Procaryotic
Reproduction Most prokaryotes can reproduce by binary fission and
at very high rates if conditions are favorable. Some prokaryotes
Form endospores, thick-coated, protective cells that are produced
within the cells when they are exposed to unfavorable conditions
Can survive very harsh conditions for extended periods, even
centuries Laura Coronado Bio 10 Chapter 15 Slide 33 Endospore
Colorized SEM Figure 15.11 Laura Coronado Bio 10 Chapter 15 Slide
34 Procaryotic Nutrition Prokaryotes exhibit four major modes of
nutrition. Phototrophs obtain energy from light. Chemotrophs obtain
energy from environmental chemicals. Species that obtain carbon
from carbon dioxide (CO 2 ) are autotrophs. Species that obtain
carbon from at least one organic nutrientthe sugar glucose, for
instanceare called heterotrophs. We can group all organisms
according to the four major modes of nutrition if we combine the
Energy source (phototroph versus chemotroph) and Carbon source
(autotroph versus heterotroph) Laura Coronado Bio 10 Chapter 15
Slide 35 Nutritional ModeEnergy SourceCarbon Source Photoautotroph
Chemoautotroph Photoheterotroph Chemoheterotroph Sunlight Inorganic
chemicals Sunlight Organic compounds CO 2 Organic compounds Figure
15.UN06 Laura Coronado Bio 10 Chapter 15 Slide 36 MODES OF
NUTRITION LightChemical Chemoautotrophs Photoautotrophs
Photoheterotrophs Chemoheterotrophs Energy source Elodea, an
aquatic plant Rhodopseudomonas Little Owl (Athene noctua) Bacteria
from a hot spring Organic compounds Carbon source CO 2 Colorized
TEM Figure 15.12 Laura Coronado Bio 10 Chapter 15 Slide 37 The Two
Main Branches of Prokaryotic Evolution: Bacteria and Archaea By
comparing diverse prokaryotes at the molecular level, biologists
have identified two major branches of prokaryotic evolution:
Bacteria Archaea (more closely related to eukaryotes) Some archaea
are extremophiles. Halophiles thrive in salty environments.
Thermophiles inhabit very hot water. Methanogens inhabit the
bottoms of lakes and swamps and aid digestion in cattle and deer.
Laura Coronado Bio 10 Chapter 15 Slide 38 (a) Salt-loving
archaea(b) Heat-loving archaea Figure 15.13 Laura Coronado Bio 10
Chapter 15 Slide 39 Bacteria and Humans Bacteria interact with
humans in many ways. Bacteria and other organisms that cause
disease are called pathogens. Most pathogenic bacteria produce
poisons. Exotoxins are poisonous proteins secreted by bacterial
cells. Endotoxins are not cell secretions but instead chemical
components of the outer membrane of certain bacteria. Laura
Coronado Bio 10 Chapter 15 Slide 40 Haemophilus influenzae Cells of
nasal lining Colorized SEM Figure 15.14 Laura Coronado Bio 10
Chapter 15 Slide 41 The best defenses against bacterial disease are
Education Sanitation Antibiotics Laura Coronado Bio 10 Chapter 15
Slide 42 Bulls-eye rash Tick that carries the Lyme disease
bacterium Spirochete that causes Lyme disease SEM Figure 15.15
Laura Coronado Bio 10 Chapter 15 Slide 43 Bioterrorism Humans have
a long and ugly history of using organisms as weapons. During the
Middle Ages, armies hurled the bodies of plague victims into enemy
ranks. Early conquerors, settlers, and warring armies in South and
North America gave native peoples items purposely contaminated with
infectious bacteria. In 1984, members of a cult in Oregon
contaminated restaurant salad bars with Salmonella bacteria. In the
fall of 2001, five Americans died from the disease anthrax in a
presumed terrorist attack. Laura Coronado Bio 10 Chapter 15 Slide
44 Figure 15.16 Laura Coronado Bio 10 Chapter 15 Slide 45 The
Ecological Impact of Prokaryotes Pathogenic bacteria are in the
minority among prokaryotes. Far more common are species that are
essential to our well-being, either directly or indirectly.
Prokaryotes play essential roles in Chemical cycles in the
environment The breakdown of organic wastes and dead organisms
Prokaryotes are used Bioremediation is the use of organisms to
remove pollutants from Water Air Soil Decomposers in sewage
treatment & petroleum spills. Laura Coronado Bio 10 Chapter 15
Slide 46 Liquid wastes Outflow Rotating spray arm Rock bed coated
with aerobic prokaryotes and fungi Figure 15.17 Laura Coronado Bio
10 Chapter 15 Slide 47 Figure 15.18 Laura Coronado Bio 10 Chapter
15 Slide 48 PROTISTS Protists Are eukaryotic Evolved from
prokaryotic ancestors Are ancestral to all other eukaryotes Plants
Fungi Animals Laura Coronado Bio 10 Chapter 15 Slide 49 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 Endosymbiosis, one species living inside another host
species, in which free-living bacteria came to reside inside a host
cell, producing mitochondria and chloroplasts Laura Coronado Bio 10
Chapter 15 Slide 50 (a) Origin of the endomembrane system(b) Origin
of mitochondria and chloroplasts Plasma membrane Ancestral
prokaryote DNA Cytoplasm Endoplasmic reticulum Membrane infolding
Nucleus Nuclear envelope Cell with nucleus and endomembrane system
Photosynthetic eukaryotic cell Photosynthetic prokaryote Aerobic
heterotrophic prokaryote Endosymbiosis (Some cells) Mitochondrion
Chloroplast Figure 15.20 Laura Coronado Bio 10 Chapter 15 Slide 51
The Diversity of Protists Protists are not one distinct group but
instead represent all the eukaryotes that are not plants, animals,
or fungi. Protists can be Unicellular Multicellular More than any
other group, protists vary in Structure Function Laura Coronado Bio
10 Chapter 15 Slide 52 Protists Classification The classification
of protists remains a work in progress. The four major categories
of protists, grouped by lifestyle, are Protozoans Slime molds
Unicellular algae Seaweeds Laura Coronado Bio 10 Chapter 15 Slide
53 Protozoans Protists that live primarily by ingesting food are
called protozoans. Protozoans with flagella are called flagellates
and are typically free-living, but sometimes are nasty parasites.
Amoebas are characterized by Great flexibility in their body shape
The absence of permanent organelles for locomotion Most species
move and feed by means of pseudopodia (singular, pseudopodium),
temporary extensions of the cell. Amoebas may have a shell, as seen
in forams, or no shell at all. Laura Coronado Bio 10 Chapter 15
Slide 54 Protozoans Apicomplexans are Named for a structure at
their apex (tip) that is specialized for penetrating host cells and
tissues All parasitic, such as Plasmodium, which causes malaria
Ciliates Are mostly free-living (nonparasitic), such as the
freshwater ciliate Paramecium Use structures called cilia to move
and feed Laura Coronado Bio 10 Chapter 15 Slide 55 A flagellate:
Giardia A foram An apicomplexan A ciliate An amoeba Another
flagellate: trypanosomes Food being ingested Pseudopodium of amoeba
Red blood cell LM TEM LM Colorized SEM Apical complex Cilia Oral
groove Figure 15.21 Laura Coronado Bio 10 Chapter 15 Slide 56 Slime
Molds Slime molds resemble fungi in appearance and lifestyle, but
the similarities are due to convergence, and slime molds are not at
all closely related to fungi. The two main groups of these protists
are Plasmodial slime molds Cellular slime molds Laura Coronado Bio
10 Chapter 15 Slide 57 Slime Molds Plasmodial slime molds Can be
large Are decomposers on forest floors Are named for the feeding
stage in their life cycle, an amoeboid mass called a plasmodium
Cellular slime molds have an interesting and complex life cycle
that changes between a Feeding stage of solitary amoeboid cells
Sluglike colony that moves and functions as a single unit Stalklike
reproductive structure Laura Coronado Bio 10 Chapter 15 Slide 58
Figure 15.22 Laura Coronado Bio 10 Chapter 15 Slide 59 LM Amoeboid
cells Slug-like colony Reproductive structure Figure 15.23 Laura
Coronado Bio 10 Chapter 15 Slide 60 Unicellular and Colonial Algae
Algae are Photosynthetic protists Found in plankton, the
communities of mostly microscopic organisms that drift or swim
weakly in aquatic environments Unicellular algae include Diatoms,
which have glassy cell walls containing silica Dinoflagellates,
with two beating flagella and external plates made of cellulose
Laura Coronado Bio 10 Chapter 15 Slide 61 Green Algae Green algae
are Unicellular Sometimes flagellated, such as Chlamydomonas
Colonial, sometimes forming a hollow ball of flagellated cells, as
seen in Volvox Laura Coronado Bio 10 Chapter 15 Slide 62 (a) A
dinoflagellate, with its wall of protective plates (c)
Chlamydomonas, a unicellular green alga with a pair of flagella (b)
A sample of diverse diatoms, which have glossy walls (d) Volvox, a
colonial green alga Colorized SEM SEM LM Figure 15.24 Laura
Coronado Bio 10 Chapter 15 Slide 63 Seaweeds Seaweeds Are only
similar to plants because of convergent evolution Are large,
multicellular marine algae Grow on or near rocky shores Are often
edible Seaweeds are classified into three different groups, based
partly on the types of pigments present in their chloroplasts:
Green algae Red algae Brown algae (including kelp) Laura Coronado
Bio 10 Chapter 15 Slide 64 Green algaeRed algaeBrown algae Figure
15.25 Laura Coronado Bio 10 Chapter 15 Slide 65 Evolution
Connection: The Origin of Multicellular Life Multicellular
organisms have interdependent, specialized cells that perform
different functions, such as feeding, waste disposal, gas exchange,
and protectionand are dependent on each other. Colonial protists
likely formed the evolutionary links between unicellular and
multicellular organisms. Laura Coronado Bio 10 Chapter 15 Slide 66
Unicellular protist Colony Locomotor cells Food-synthesizing cells
Early multicellular organism with specialized, interdependent cells
Later organism with gametes and somatic cells Somatic cells Gamete
Figure 15.26-3 Laura Coronado Bio 10 Chapter 15
