1. © 2010 Pearson Education, Inc.
 Welcome to Chapter 15

2. © 2010 Pearson Education, Inc.
MAJOR EPISODES IN THE HISTORY OF
LIFE
• Earth was formed about 4.6 billion years ago.
• Prokaryotes
– Evolved by 3.5 billion years ago
– 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.

4. Paleozoic Mesozoic Cenozoic
Bacteria
Archaea
Plants
Fungi
Animals
ProkaryotesEukaryotes
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
2,000 1,500 1,000 500 0
Figure 15.1b

5. © 2010 Pearson Education, Inc.
• 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

6. © 2010 Pearson Education, Inc.
• We can use a clock analogy to look at the major events in the
history of life on Earth

7. Humans
Origin of solar
system and Earth
1 4
0
2 3
Present
Anim
als
Coloniz
of land
ation
Multi
eukar
cellular
yotes
Sing
eukar
cel
yotes
le-
led
Atmo
oxy
spheric gen
Bil
arsons of
ago
ye
li
karyotes
Pro Figure 15.2

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THE ORIGIN OF LIFE
• We may never know for sure how life on Earth began.

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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 19th
century, 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
produced simple cells by chemical and physical processes.

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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

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From Chemical Evolution to Darwinian Evolution
• Over millions of years
– Natural selection favored the most efficient cells
– The first prokaryotic cells evolved

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PROKARYOTES
• Prokaryotes lived and evolved all alone on Earth for 2 billion
years before eukaryotes evolved.

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They’re Everywhere!
• Prokaryotes
– Are found wherever there is life
– Far outnumber eukaryotes
– Can cause disease
– Can be beneficial

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• 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.

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• Compared to eukaryotes, prokaryotes are
– Much more abundant
– Typically much smaller

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• 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

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The Structure and Function of Prokaryotes
• Prokaryotic cells
– Lack true nuclei
– Lack other membrane-enclosed organelles
– Have cell walls exterior to their plasma membranes

19. Plasma membrane
(encloses cytoplasm)
Cell wall (provides
Rigidity)
Capsule (sticky
coating)
Prokaryotic
flagellum
(for propulsion)
Ribosomes
(synthesize
proteins)
Nucleoid
(contains DNA)
Pili (attachment structures)
ColorizedTEM
Figure 4.4

20. © 2010 Pearson Education, Inc.
• Prokaryotes come in several shapes:
– Spherical (cocci)
– Rod-shaped (bacilli)
– Spiral
Procaryotic Forms

21. ColorizedSEM
Figure 15.8a

22. ColorizedSEM
Figure 15.8b

23. ColorizedTEM
Figure 15.8c

24. © 2010 Pearson Education, Inc.
• Most prokaryotes are
– Unicellular
– Very small
• Some prokaryotes
– Form true colonies
– Show specialization of cells
– Are very large
Video: Cyanobacteria (Oscillatoria)

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• 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.
Video: Prokaryotic Flagella (Salmonella typhimurium) (random)

26. Plasma
membrane
Cell wall
Rotary movement of
each flagellum
Flagellum
ColorizedTEM
Figure 15.10

27. © 2010 Pearson Education, Inc.
• 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
Procaryotic Reproduction

28. Endospore
ColorizedSEM
Figure 15.11

29. © 2010 Pearson Education, Inc.
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 (CO2) are autotrophs.
– Species that obtain carbon from at least one organic nutrient—the sugar
glucose, for instance—are called heterotrophs.

30. © 2010 Pearson Education, Inc.
• 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)

31. MODES OF NUTRITION
Light Chemical
ChemoautotrophsPhotoautotrophs
Photoheterotrophs Chemoheterotrophs
Energy source
Elodea, an aquatic plant
Rhodopseudomonas Little Owl (Athene noctua)
Bacteria from a hot spring
Organiccompounds
Carbonsource
CO2
ColorizedTEM
ColorizedTEM
Figure 15.12

32. 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)
– clip
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33. © 2010 Pearson Education, Inc.
• Some archaea are “extremophiles.”
– Halophiles thrive in salty environments.
– Thermophiles inhabit very hot water.

34. (a) Salt-loving archaea (b) Heat-loving archaea
Figure 15.13

35. (a) Salt-loving archaea
Figure 15.13a

36. (b) Heat-loving archaea
Figure 15.13b

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Bacteria and Humans
• Bacteria interact with humans in many ways.

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Bacteria That Cause Disease
• 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.

39. Haemophilus
influenzae
Cells of nasal
lining
ColorizedSEM
Figure 15.14

40. © 2010 Pearson Education, Inc.
• The best defenses against bacterial disease are
– Sanitation
– Antibiotics
– Education

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• Lyme disease is
– Caused by bacteria carried by ticks
– Treated with antibiotics

42. “Bull’s-eye” rash
Tick that carries the
Lyme disease bacterium
Spirochete that causes
Lyme disease
SEM
Figure 15.15

43. Tick that carries the Lyme disease bacterium
Figure 15.15b

44. Figure 15.15c

45. Spirochete that causes Lyme disease
Figure 15.15d

46. © 2010 Pearson Education, Inc.
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.

47. Figure 15.16

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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.

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Prokaryotes and Chemical Recycling
• Prokaryotes play essential roles in
– Chemical cycles in the environment
– The breakdown of organic wastes and dead organisms

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Prokaryotes and Bioremediation
• Bioremediation is the use of organisms to remove pollutants
from
– Water
– Air
– Soil
• A familiar example is the use of prokaryotic decomposers in
sewage treatment.

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• Certain bacteria
– Can decompose petroleum
– Are useful in cleaning up oil spills

52. Figure 15.18

53. © 2010 Pearson Education, Inc.
PROTISTS
• Protists
– Are eukaryotic
– Evolved from prokaryotic ancestors

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The Diversity of Protists
• Protists can be
– Unicellular
– Multicellular
• More than any other group, protists vary in
– Structure
– Function

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• Protists are not one distinct group but instead represent all the
eukaryotes that are not plants, animals, or fungi.

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• 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

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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 parasites.
Video: Euglena Motion

58. A flagellate: Giardia
ColorizedSEM
Figure 15.21a

59. Another flagellate: trypanosomes
ColorizedSEM
Figure 15.21b

60. © 2010 Pearson Education, Inc.
• 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.
Video: Amoeba Pseudopodia
Video: Amoeba

61. An amoeba
LM
Figure 15.21c

62. © 2010 Pearson Education, Inc.
• 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

63. An apicomplexan
TEM
Figure 15.21e

64. © 2010 Pearson Education, Inc.
• Ciliates
– Are mostly free-living (nonparasitic), such as the freshwater ciliate
Paramecium
– Use structures called cilia to move and feed
Video: Paramecium Vacuole
Video: Paramecium Cilia
Video: Vorticella Habitat
Video: Vorticella Detail
Video: Vorticella Cilia

65. A ciliate
LM
Figure 15.21f

66. © 2010 Pearson Education, Inc.
Slime Molds
• The two main groups of these protists are
– Plasmodial slime molds
– Cellular slime molds

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• Plasmodial slime molds
– Can be large
– Are decomposers on forest floors
Video: Plasmodial Slime Mold
Video: Plasmodial Slime Mold Streaming

68. © 2010 Pearson Education, Inc.
• Cellular slime molds have an interesting and complex life cycle
that changes between a

69. © 2010 Pearson Education, Inc.
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

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• Unicellular algae include
– Diatoms, which have glassy cell walls containing silica
– Dinoflagellates, with two beating flagella and external plates made of
cellulose

71. (a) A dinoflagellate, with its wall of protective plates
SEM
Figure 15.24a

72. b) A sample of diverse diatoms, which have glossy walls
LM
Figure 15.24b

73. © 2010 Pearson Education, Inc.
• Green algae are
– Unicellular
– Sometimes flagellated, such as Chlamydomonas
– Colonial, sometimes forming a hollow ball of flagellated cells, as seen in
Volvox
Video: Volvox Flagella
Video: Volvox Daughter
Video: Volvox Colony
Video: Chlamydomonas

74. (d) Volvox, a colonial green alga
LM
Figure 15.24d

75. (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
ColorizedSEMSEM
LMLM
Figure 15.24

76. © 2010 Pearson Education, Inc.
Seaweeds
• Seaweeds
– Are large, multicellular marine algae
– Grow on or near rocky shores
– Are often edible

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• 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)

78. Green algae Red algae Brown algae
Figure 15.25

79. Green algae
Figure 15.25a

80. Red algae
Figure 15.25b

81. Brown algae
Figure 15.25c

82. Figure 15.UN01
Bacteria
Archaea
Prokaryotes
Eukarya
Protists
Plants
Fungi
Animals

83. Bacteria
Archaea
Prokaryotes
Eukarya
Protists
Plants
Fungi
Animals
Figure 15.UN02

84. Major episode Millions of years ago
All major animal phyla established
Plants and fungi colonize land
Origin of Earth
First multicellular organisms
Oldest eukaryotic fossils
Accumulation of O2 in atmosphere
Oldest prokaryotic fossils
500
530
1,200
1,800
2,400
3,500
4,600
Figure 15.UN03

85. 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

86. Spherical Rod-shaped Spiral
Figure 15.UN05

87. Nutritional Mode Energy Source Carbon Source
Photoautotroph
Chemoautotroph
Photoheterotroph
Chemoheterotroph
Sunlight
Inorganic chemicals
Sunlight
Organic compounds
CO2
Organic compounds
Figure 15.UN06

88. Bacteria
Archaea
Prokaryotes
Eukarya
Protists
Plants
Fungi
Animals
Figure 15.UN07

89. Bacteria
Archaea
Prokaryotes
Eukarya
Protists
Plants
Fungi
Animals
Figure 15.UN08