15 lecture presentation0

© 2010 Pearson Education, Inc.

Welcome to Chapter 15


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


• Single-celled eukaryotes first evolved about 2.1 billion years ago.

• Multicellular eukaryotes first evolved at least 1.2 billion years ago.

Paleozoic Mesozoic Cenozoic

Bacteria

Archaea

Plants

Fungi

Animals

Pro

ka

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sE

uk

ary

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s

Pro

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Oldest eukaryoticfossils

Origin ofmulticellularorganisms

Oldestanimalfossils

Plants andsymbiotic fungicolonize land

Extinction ofdinosaurs

First humans

Millions of years ago

Cambrianexplosion

2,000 1,500 1,000 500 0

Figure 15.1b


• 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


• We can use a clock analogy to look at the major events in the history of life on Earth

Humans

Origin of solarsystem and Earth

1 4

0

2 3

Present

Animals

Colonizof land

ation

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Figure 15.2


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


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.


• Today, most biologists think it is possible that life on early Earth produced simple cells by chemical and physical processes.


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


From Chemical Evolution to Darwinian Evolution• Over millions of years

– Natural selection favored the most efficient cells

– The first prokaryotic cells evolved


PROKARYOTES• Prokaryotes lived and evolved all alone on Earth for 2 billion

years before eukaryotes evolved.


They’re Everywhere!• Prokaryotes

– 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.


• 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


The Structure and Function of Prokaryotes• Prokaryotic cells

– Lack true nuclei

– Lack other membrane-enclosed organelles

– Have cell walls exterior to their plasma membranes

Plasma membrane(encloses cytoplasm)

Cell wall (providesRigidity)

Capsule (stickycoating)

Prokaryoticflagellum(for propulsion)

Ribosomes(synthesizeproteins)

Nucleoid(contains DNA)

Pili (attachment structures)

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Figure 4.4


• Prokaryotes come in several shapes:

– Spherical (cocci)

– Rod-shaped (bacilli)

– Spiral

Procaryotic Forms

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Figure 15.8a

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Figure 15.8b

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Figure 15.8c


• Most prokaryotes are

– Unicellular

– Very small

• Some prokaryotes

– Form true colonies

– Show specialization of cells

– Are very large

Video: Cyanobacteria (Oscillatoria)


• 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)

Plasmamembrane

Cell wall

Rotary movement ofeach flagellum

Flagellum

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Figure 15.10


• 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

Endospore

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Figure 15.11


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.


• 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)

MODES OF NUTRITION

Light Chemical

ChemoautotrophsPhotoautotrophs

Photoheterotrophs Chemoheterotrophs

Energy source

Elodea, an aquatic plant

Rhodopseudomonas Little Owl (Athene noctua)

Bacteria from a hot spring

Org

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Figure 15.12

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



• Some archaea are “extremophiles.”

– Halophiles thrive in salty environments.

– Thermophiles inhabit very hot water.

(a) Salt-loving archaea (b) Heat-loving archaea

Figure 15.13

(a) Salt-loving archaeaFigure 15.13a

(b) Heat-loving archaeaFigure 15.13b


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


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.

Haemophilusinfluenzae

Cells of nasallining

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Figure 15.14


• The best defenses against bacterial disease are

– Sanitation

– Antibiotics

– Education


• Lyme disease is

– Caused by bacteria carried by ticks

– Treated with antibiotics

“Bull’s-eye” rash

Tick that carries theLyme disease bacterium

Spirochete that causesLyme disease

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Figure 15.15

Tick that carries the Lyme disease bacteriumFigure 15.15b

Figure 15.15c

Spirochete that causes Lyme diseaseFigure 15.15d


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.

Figure 15.16


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 and Chemical Recycling

• Prokaryotes play essential roles in

– Chemical cycles in the environment

– The breakdown of organic wastes and dead organisms


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.


• Certain bacteria

– Can decompose petroleum

– Are useful in cleaning up oil spills

Figure 15.18


PROTISTS• Protists

– Are eukaryotic

– Evolved from prokaryotic ancestors


The Diversity of Protists• Protists can be

– Unicellular

– Multicellular

• More than any other group, protists vary in

– Structure

– Function


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


• 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


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

A flagellate: Giardia

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Figure 15.21a

Another flagellate: trypanosomes

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Figure 15.21b


• 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

An amoeba

LM

Figure 15.21c


• 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

An apicomplexan

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Figure 15.21e


• 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

A ciliate

LM

Figure 15.21f


Slime Molds

• The two main groups of these protists are

– Plasmodial slime molds

– Cellular slime molds


• Plasmodial slime molds

– Can be large

– Are decomposers on forest floors

Video: Plasmodial Slime Mold

Video: Plasmodial Slime Mold Streaming


• Cellular slime molds have an interesting and complex life cycle that changes between a


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

(a) A dinoflagellate, with its wall of protective plates

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Figure 15.24a

(b) A sample of diverse diatoms, which have glossy walls

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Figure 15.24b


• 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

(d) Volvox, a colonial green alga

LM

Figure 15.24d

(a) A dinoflagellate, with its wallof protective plates

(c) Chlamydomonas, a unicellulargreen alga with a pair of flagella

(b) A sample of diverse diatoms,which have glossy walls

(d) Volvox, a colonial green alga

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Figure 15.24


Seaweeds

• Seaweeds

– 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)

Green algae Red algae Brown algae

Figure 15.25

Green algaeFigure 15.25a

Red algaeFigure 15.25b

Brown algaeFigure 15.25c

Figure 15.UN01

Bacteria

Archaea

Prokaryotes

Eukarya

Protists

Plants

Fungi

Animals

Bacteria

Archaea

Prokaryotes

Eukarya

Protists

Plants

Fungi

Animals

Figure 15.UN02

Major episode Millions of years ago

All major animal phyla established

Plants and fungi colonize land

Origin of Earth

First multicellular organismsOldest eukaryotic fossils

Accumulation of O2 in atmosphereOldest prokaryotic fossils

5005301,2001,800

2,4003,5004,600

Figure 15.UN03

Inorganic compounds

Abiotic synthesisof organic monomers

Abiotic synthesisof polymers

Formationof pre-cells

Self-replicatingmolecules

Membrane-enclosed compartment

Complementarychain

Polymer

Organic monomers

Figure 15.UN04

Spherical Rod-shaped Spiral

Figure 15.UN05

Nutritional Mode Energy Source Carbon Source

Photoautotroph

Chemoautotroph

Photoheterotroph

Chemoheterotroph

Sunlight

Inorganic chemicals

Sunlight

Organic compounds

CO2

Organic compounds

Figure 15.UN06

Bacteria

Archaea

Prokaryotes

Eukarya

Protists

Plants

Fungi

Animals

Figure 15.UN07

Bacteria

Archaea

Prokaryotes

Eukarya

Protists

Plants

Fungi

Animals

Figure 15.UN08

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prokaryotes prokaryotes

prokaryotes form endospores

origin of life

history of life earth

humans millions of years

simple cells

specialization of cells