BDOL Interactive Chalkboard

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Table of Contents pages iv-v
Unit 1 What is Biology? Unit 2 Ecology Unit
3 The Life of a Cell Unit 4 Genetics Unit 5
Change Through Time Unit 6 Viruses, Bacteria,
Protists, and Fungi Unit 7 Plants Unit 8
Invertebrates Unit 9 Vertebrates Unit 10 The
Human Body
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Table of Contents pages iv-v
Unit 1 What is Biology? Chapter 1
Biology The Study of Life Unit 2 Ecology
Chapter 2 Principles of Ecology Chapter
3 Communities and Biomes Chapter 4
Population Biology Chapter 5 Biological
Diversity and Conservation Unit 3 The Life of a
Cell Chapter 6 The Chemistry of Life
Chapter 7 A View of the Cell Chapter 8
Cellular Transport and the Cell Cycle
Chapter 9 Energy in a Cell
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Table of Contents pages iv-v
Unit 4 Genetics Chapter 10 Mendel and
Meiosis Chapter 11 DNA and Genes
Chapter 12 Patterns of Heredity and Human
Genetics Chapter 13 Genetic Technology Unit
5 Change Through Time Chapter 14 The
History of Life Chapter 15 The Theory of
Evolution Chapter 16 Primate Evolution
Chapter 17 Organizing Lifes Diversity
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Table of Contents pages iv-v
Unit 6 Viruses, Bacteria, Protists, and Fungi
Chapter 18 Viruses and Bacteria Chapter
19 Protists Chapter 20 Fungi Unit 7
Plants Chapter 21 What Is a Plant?
Chapter 22 The Diversity of Plants
Chapter 23 Plant Structure and Function
Chapter 24 Reproduction in Plants
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Table of Contents pages iv-v
Unit 8 Invertebrates Chapter 25 What Is
an Animal? Chapter 26 Sponges,
Cnidarians, Flatworms, and
Roundworms Chapter 27
Mollusks and Segmented Worms Chapter 28
Arthropods Chapter 29 Echinoderms and
Invertebrate
Chordates
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Table of Contents pages iv-v
Unit 9 Vertebrates Chapter 30 Fishes
and Amphibians Chapter 31 Reptiles and
Birds Chapter 32 Mammals Chapter 33
Animal Behavior Unit 10 The Human Body
Chapter 34 Protection, Support, and
Locomotion Chapter 35 The Digestive and
Endocrine Systems Chapter 36 The Nervous
System Chapter 37 Respiration,
Circulation, and Excretion Chapter 38
Reproduction and Development Chapter 39
Immunity from Disease
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Unit Overview pages 366-367
Changes Through Time
The History of Life
The Theory of Evolution
Primate Evolution
Organizing Lifes Diversity
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Chapter Contents page ix
Chapter 14 The History of Life 14.1 The Record
of Life 14.1 Section Check 14.2 The Origin
of Life 14.2 Section Check Chapter 14 Summary
Chapter 14 Assessment
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Chapter Intro-page 368
What Youll Learn
You will examine how rocks and fossils provide
evidence of changes in Earths organisms.
You will correlate the geologic time scale with
biological events.
You will sequence the steps by which small
molecules may have produced living cells.
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14.1 Section Objectives page 369
Section Objectives

• Identify the different types of fossils and how
  they are formed

• Summarize the major events of the geologic time
  scale.

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Section 14.1 Summary pages 369-379
Early History of Earth

• What was early Earth like? Some scientists
  suggest that it was probably very hot. The
  energy from colliding meteorites could have
  heated its surface, while both the compression of
  minerals and the decay of radioactive materials
  heated its interior.

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Section 14.1 Summary pages 369-379
Early History of Earth

• Volcanoes might have frequently spewed lava and
  gases, relieving some of the pressure in Earths
  hot interior. These gases helped form Earths
  early atmosphere.

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Section 14.1 Summary pages 369-379
Early History of Earth

• About 4.4 billion years ago, Earth might have
  cooled enough for the water in its atmosphere to
  condense. This might have led to millions of
  years of rainstorms with lightningenough rain to
  fill depressions that became Earths oceans.

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Section 14.1 Summary pages 369-379
History in Rocks

• There is no direct evidence of the earliest years
  of Earths history. The oldest rocks that have
  been found on Earth formed about 3.9 billion
  years ago.

• Although rocks cannot provide information about
  Earths infancy, they are an important source of
  information about the diversity of life that has
  existed on the planet.

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Section 14.1 Summary pages 369-379
Fossils-Clues to the past

• About 95 percent of the species that have existed
  are extinctthey no longer live on Earth.

• Among other techniques, scientists study fossils
  to learn about ancient species.

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Section 14.1 Summary pages 369-379
Fossils-Clues to the past
Types of Fossils

• A fossil is evidence of an organism that lived
  long ago that is preserved in Earths rocks.

Formation
Fossils Types
A trace fossil is any indirect evidence
A trace fossil is any indirect evidence
Trace fossils
left by an animal and may include a
footprint, a trail, or a burrow.
When minerals in rocks fill a space
Casts
left by a decayed organism, they make
a replica, or cast, of the organism.
A mold forms when an organism is
A mold forms when an organism is
Molds
buried in sediment and then decays,
leaving an empty space.
Petrified/
Petrified-minerals sometimes penetrate
and replace the hard parts of an
Permineralized
organism. Permineralized-void spaces
fossils
in original organism infilled by
minerals.
Amber-
At times, an entire organism was
Preserved or
quickly trapped in ice or tree sap that
frozen fossils
hardened into amber.
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Section 14.1 Summary pages 369-379
Paleontologists-Detectives to the past

• Paleontologists, scientists who study ancient
  life, are like detectives who use fossils to
  understand events that happened long ago.

• They use fossils to determine the kinds of
  organisms that lived during the past and
  sometimes to learn about their behavior.

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Section 14.1 Summary pages 369-379
Paleontologists-Detectives to the past

• Paleontologists also study fossils to gain
  knowledge about ancient climate and geography.

• By studying the condition, position, and location
  of rocks and fossils, geologists and
  paleontologists can make deductions about the
  geography of past environments.

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Section 14.1 Summary pages 369-379
Fossil formation

• For fossils to form, organisms usually have to be
  buried in mud, sand, or clay soon after they die.

• Most fossils are found in sedimentary rocks.
  These rocks form at relatively low temperatures
  and pressures that may prevent damage to the
  organism.

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Section 14.1 Summary pages 369-379
Fossil formation

• Fossils are not usually found in other types of
  rock because of the ways those rocks form. For
  example, the conditions under which metamorphic
  rocks form often destroy any fossils that were in
  the original sedimentary rock.

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Section 14.1 Summary pages 369-379
The Fossilization Process

• Few organisms become fossilized because, without
  burial, bacteria and fungi immediately decompose
  their dead bodies. Occasionally, however,
  organisms do become fossils in a process that
  usually takes many years.

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Section 14.1 Summary pages 369-379
The Fossilization Process

• A Protoceratops drinking at a river falls into
  the water and drowns

• Sediments from upstream rapidly cover the body,
  slowing its decomposition. Minerals from the
  sediments seep into the body.

• Earth movements or erosion may expose the
  fossil millions of years after it formed.

• Over time, additional layers of sediment
  compress the sediments around the body, forming
  rock. Minerals eventually replace all the bodys
  bone material.

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Section 14.1 Summary pages 369-379
Relative dating

• Scientists use a variety of methods to determine
  the age of fossils. One method is a technique
  called relative dating.

• If the rock layers have not been disturbed, the
  layers at the surface must be younger than the
  deeper layers.

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Section 14.1 Summary pages 369-379
Relative dating

• The fossils in the top layer must also be younger
  than those in deeper layers.

• Using this principle, scientists can determine
  relative age and the order of appearance of the
  species that are preserved as fossils in the
  layers.

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Section 14.1 Summary pages 369-379
Radiometric dating

• To find the specific ages of rocks, scientists
  use radiometric dating techniques utilizing the
  radioactive isotopes in rocks.

• Recall that radioactive isotopes are atoms with
  unstable nuclei that break down, or decay, over
  time, giving off radiation.

• A radioactive isotope forms a new isotope after
  it decays.

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Section 14.1 Summary pages 369-379
Radiometric dating

• Because every radioactive isotope has a
  characteristic decay rate, scientists use the
  rate of decay as a type of clock.

• The decay rate of a radioactive isotope is called
  its half-life.

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Section 14.1 Summary pages 369-379
Radiometric dating

• Scientists try to determine the approximate ages
  of rocks by comparing the amount of a radioactive
  isotope and the new isotope into which it decays.

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Section 14.1 Summary pages 369-379
Radiometric dating

• Scientists use potassium-40, a radioactive
  isotope that decays to argon-40, to date rocks
  containing potassium bearing minerals.

• Based on chemical analysis, chemists have
  determined that potassium-40 decays to half its
  original amount in 1.3 billion years.

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Section 14.1 Summary pages 369-379
Radiometric dating

• Scientists use carbon-14 to date fossils less
  than 70 000 years old.

• Again, based on chemical analysis, they know that
  carbon-14 decays to half its original amount in
  5730 years.

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Section 14.1 Summary pages 369-379
Radiometric dating

• Scientists always analyze many samples of a rock
  using as many methods as possible to obtain
  consistent values for the rocks age.

• Errors can occur if the rock has been heated,
  causing some of the radioactive isotopes to be
  lost or gained.

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Section 14.1 Summary pages 369-379
A Trip Through Geologic Time

• By examining sequences containing sedimentary
  rock and fossils and dating some or the igneous
  or metamorphic rocks that are found in the
  sequences, scientists have put together a
  chronology, or calendar, of Earths history.

• This chronology, called the geologic time scale,
  is based on evidence from Earths rocks and
  fossils.

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Section 14.1 Summary pages 369-379
The geologic time scale

• Rather than being based on months or even years,
  the geologic time scale is divided into four
  large sections, the Precambrian (pree KAM bree
  un) Era,
• the Paleozoic (pay lee uh ZOH ihk) Era,
• the Mesozoic (me zuh ZOH ihk) Era,
• and the Cenozoic (se nuh ZOH ihk) Era.

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Section 14.1 Summary pages 369-379
The geologic time scale

• An era is a large division in the scale and
  represents a very long period of time.

• Each era is subdivided into periods.

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Section 14.1 Summary pages 369-379
The geologic time scale

• The divisions in the geologic time scale are
  distinguished by the organisms that lived during
  that time interval.

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Section 14.1 Summary pages 369-379
The geologic time scale

• The fossil record indicates that there were
  several episodes of mass extinction that fall
  between time divisions.

• A mass extinction is an event that occurs when
  many organisms disappear from the fossil record
  almost at once.

• The geologic time scale begins with the formation
  of Earth about 4.6 billion years ago.

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Section 14.1 Summary pages 369-379
Life during the Precambrian

• The oldest fossils are found in Precambrian rocks
  that are about 3.4 billion years old.

• Scientists found these fossils, in rocks found in
  the deserts of western Australia.

• The fossils resemble the forms of modern species
  of photosynthetic cyanobacteria.

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Section 14.1 Summary pages 369-379
Life during the Precambrian

• Scientists have also found dome-shaped structures
  called stromatolites (stroh MAT ul ites) in
  Australia and on other continents.

• Stromatolites still form today in Australia from
  mats of cyanobacteria. Thus, the stromatolites
  are evidence of the existence of photosynthetic
  organisms on Earth during the Precambrian.

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Section 14.1 Summary pages 369-379
Life during the Precambrian

• The Precambrian accounts for about 87 percent of
  Earths history.

• At the beginning of the Precambrian, unicellular
  prokarotescells that do not have a
  membrane-bound nucleus appear to have been the
  only life forms on Earth.

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Section 14.1 Summary pages 369-379
Life during the Precambrian

• About 1.8 billion years ago, the fossil record
  shows that more complex eukaryotic organisms,
  living things with membrane-bound nuclei in their
  cells, appeared.

Major Life Form
Invertebrates
Prokaryotes
Life evolves
Eukaryotes
Major Events
Period Era
Precambrian
4000
3500
1800
Million Years Ago
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Section 14.1 Summary pages 369-379
Life during the Precambrian

• By the end of the Precambrian, about 543 million
  years ago, multicellular eukaryotes, such as
  sponges and jelly-fishes, diversified and filled
  the oceans.

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Section 14.1 Summary pages 369-379
Diversity during the Paleozoic

• In the Paleozoic Era, which lasted until 248
  million years ago, many more types of animals and
  plants were present on Earth, and some were
  preserved in the fossil record.

• During the Cambrian Period, the oceans teemed
  with many types of animals, including worms, sea
  stars, and unusual arthropods.

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Section 14.1 Summary pages 369-379
Diversity during the Paleozoic

• During the first half of the Paleozoic, fishes,
  the oldest animals with backbones, appeared in
  Earths waters.

• There is also fossil evidence of ferns and early
  seed plants existing on land about 400 million
  years ago.

• Around the middle of the Paleozoic, four-legged
  animals such as amphibians appeared on Earth.

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Section 14.1 Summary pages 369-379
Diversity during the Paleozoic

• During the last half of the era, the fossil
  record shows that reptiles appeared and began to
  flourish on land.

First jawed fishes
First land plants
Conifers dominant
First vertebrates
First amphibians
First seed plants
First reptiles
Carboniferous
Permian
Cambrian
Ordovician
Silurian
Devonian
Paleozoic Era
543
491
443
417
354
323
290
Million Years Ago
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Section 14.1 Summary pages 369-379
Diversity during the Paleozoic

• The largest mass extinction recorded in the
  fossil record marked the end of the Paleozoic.

• About 90 percent of Earths marine species and 70
  percent of the land species disappeared at this
  time.

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Section 14.1 Summary pages 369-379
Life in the Mesozoic

• The Mesozoic Era began about 248 million years
  ago.

• The Mesozoic Era is divided into three periods.

• Fossils from the Triassic Period, the oldest
  period, show that mammals appeared on Earth at
  this time.

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Section 14.1 Summary pages 369-379
Life in the Mesozoic

• These fossils of mammals indicate that early
  mammals were small and mouse-like.

Flowering plants dominant
First flowering plants
First dinosaurs
First mammals
First birds
Period
Triassic
Jurassic
Cretaceous
Era
Mesozoic Era
248
144
206
Million Years Ago
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Section 14.1 Summary pages 369-379
Life in the Mesozoic

• The middle of the Mesozoic, called the Jurassic
  Period, began about 206 million years ago.

Flowering plants dominant
First flowering plants
First dinosaurs
First mammals
First birds
Period
Triassic
Jurassic
Cretaceous
Era
Mesozoic Era
248
144
206
Million Years Ago
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Section 14.1 Summary pages 369-379
Life in the Mesozoic

• Recent fossil discoveries support the idea that
  modern birds evolved from one of the groups of
  dinosaurs toward the end of this period.

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Section 14.1 Summary pages 369-379
A mass extinction

• The last period in the Mesozoic, the Cretaceous,
  began about 144 million years ago.

• During this period, many new types of mammals
  appeared and flowering plants flourished on Earth.

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Section 14.1 Summary pages 369-379
A mass extinction

• The mass extinction of the dinosaurs marked the
  end of the Cretaceous Period about 65 million
  years ago.

• Some scientists propose that a large meteorite
  collision caused this mass extinction.

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Section 14.1 Summary pages 369-379
Changes during the Mesozoic

• The theory of continental drift, suggests that
  Earths continents have moved during Earths
  history and are still moving today at a rate of
  about six centimeters per year.

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Section 14.1 Summary pages 369-379
Changes during the Mesozoic
Click image to view movie.
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Section 14.1 Summary pages 369-379
Changes during the Mesozoic

• Early in the Mesozoic, the continents were merged
  into one large landmass. During the era, this
  super-continent broke up and the pieces drifted
  apart.

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Section 14.1 Summary pages 369-379
Changes during the Mesozoic

• The theory for how the continents move is called
  plate tectonics.

• According to this idea, Earths surface consists
  of several rigid plates that drift on top of a
  plastic, partially molten layer of rock.

• These plates are continually moving-spreading
  apart, sliding by, or pushing against each other.
  The movements affect organisms.

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Section 14.1 Summary pages 369-379
The Cenozoic Era

• The Cenozoic began about 65 million years ago.

• It is the era in which you now live. Mammals
  began to flourish during the early part of this
  era.

• Primates first appeared approximately 75 million
  years ago and have diversified greatly.

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Section 14.1 Summary pages 369-379
The Cenozoic Era

• The modern human species appeared perhaps as
  recently as 200,000 years ago.

Mammals dominant
Humans evolve
Tertiary
Quaternary
Period Era
Cenozoic Era
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1.8
Million Years Ago
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Section 1 Check
Question 1
What determines the divisions in the geologic
time scale?
A. the types of rock formed during the different
divisions
B. dates based upon radioactive isotope decay
C. periodic episodes of mass extinction
D. the organisms that lived during that time
interval
IN 1.32
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Section 1 Check
The answer is D, the organisms that lived during
that time interval.
IN 1.32
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Section 1 Check
Question 2
How can scientists determine when a mass
extinction occurred in Earths history?
Answer
The fossils from a large percentage of species
disappear from the fossil record almost at once.
IN 1.32
61
Section 1 Check
Question 3
What organisms have occupied Earth for the
longest period of time?
A. single-celled organisms
B. mammals
C. reptiles
D. land plants
IN 1.33
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Section 1 Check
The answer is A. Single-celled organisms have
been present on the Earth since the Precambrian
period and are still present today.
IN 1.33
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Section 1 Check
Question 4
Given that volcanoes have erupted since Earths
early history, why does volcanic rock not contain
many fossils?
Answer
Lava is subject to high heat and strong pressure
changes that prevent fossils from forming in it.
IN 1.32
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Section 1 Check
Question 5
If scientists discover an early human fossil
lying next to a dinosaur fossil, might they infer
that some early humans actually lived at the time
of dinosaurs?
Answer
The answer is no. The two fossils may have come
to lie next to one another because of the effects
of erosion, earth movements, the movement of
water, or other artificial means.
IN 1.32
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14.2 Section Objectives page 380
Section Objectives

• Analyze early experiments that support the
  concept of biogenesis.

• Review, analyze, and critique modern theories of
  the origin of life.

• Relate hypotheses about the origin of cells to
  the environmental conditions of early Earth.

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Section 14.2 Summary pages 380-385
Origins The Early Idea

• In the past, the ideas that decaying meat
  produced maggots, mud produced fishes, and grain
  produced mice were reasonable explanations for
  what people observed occurring in their
  environment.

• Such observations led people to believe in
  spontaneous generationthe idea that nonliving
  material can produce life.

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Section 14.2 Summary pages 380-385
Spontaneous generation is disproved

• In 1668, an Italian physician, Francesco Redi,
  disproved a commonly held belief at the timethe
  idea that decaying meat produced maggots, which
  are immature flies.

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Section 14.2 Summary pages 380-385
Spontaneous generation is disproved

• Redis well-designed, controlled experiment
  successfully convinced many scientists that
  maggots, and probably most large organisms, did
  not arise by spontaneous generation.

Control group
Time
Time
Experimental group
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Section 14.2 Summary pages 380-385
Spontaneous generation is disproved

• However, during Redis time, scientists began to
  use the latest tool in biologythe microscope.

• Although Redi had disproved the spontaneous
  generation of large organisms, many scientists
  thought that microorganisms were so numerous and
  widespread that they must arise
  spontaneously-probably from a vital force in the
  air.

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Section 14.2 Summary pages 380-385
Pasteurs experiments

• In the mid-1800s, Louis Pasteur designed an
  experiment that disproved the spontaneous
  generation of microorganisms.

• Pasteur set up an experiment in which air, but no
  microorganisms, was allowed to contact a broth
  that contained nutrients.

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Section 14.2 Summary pages 380-385
Pasteurs experiments
The flasks S-shaped neck allowed air to enter,
but prevented microorganisms from entering the
flask.
Each of Pasteurs broth-filled flasks was boiled
to kill all microorganisms.
Microorganisms soon grew in the broth,
showing that they come from other microorganisms.
Pasteur tilted a flask, allowing the
microorganisms to enter the broth.
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Section 14.2 Summary pages 380-385
Pasteurs experiments

• Pasteurs experiment showed that microorganisms
  do not simply arise in broth, even in the
  presence of air.

• From that time on, biogenesis (bi oh JEN uh sus),
  the idea that living organisms come only from
  other living organisms, became a cornerstone of
  biology.

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Section 14.2 Summary pages 380-385
Origins The Modern Ideas

• No one has yet proven scientifically how life on
  Earth began.

• However, scientists have developed theories about
  the origin of life on Earth from testing
  scientific hypotheses about conditions on early
  Earth.

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Section 14.2 Summary pages 380-385
Simple organic molecules formed

• Scientists hypothesize that two developments must
  have preceded the appearance of life on Earth.

• First, simple organic molecules, or molecules
  that contain carbon, must have formed.

• Then these molecules must have become organized
  into complex organic molecules such as proteins,
  carbohydrates, and nucleic acids that are
  essential to life.

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Section 14.2 Summary pages 380-385
Simple organic molecules formed

• In the 1930s, a Russian scientist, Alexander
  Oparin, hypothesized that life began in the
  oceans that formed on early Earth.

• He suggested that energy from the sun, lightning,
  and Earths heat triggered chemical reactions to
  produce small organic molecules from the
  substances present in the atmosphere.

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Section 14.2 Summary pages 380-385
Simple organic molecules formed

• Then, rain probably washed the molecules into the
  oceans to form what is often called a primordial
  soup.

• In 1953, two American scientists, Stanley Miller
  and Harold Urey, tested Oparins hypothesis by
  simulating the conditions of early Earth in the
  laboratory.

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Section 14.2 Summary pages 380-385
Simple organic molecules formed
Entry for hydrogen, methane, and ammonia gases
Electrode
High voltage source
Condenser for cooling
Boiling water
Solution of organic compounds
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Section 14.2 Summary pages 380-385
The formation of protocells

• The next step in the origin of life, as proposed
  by some scientists, was the formation of complex
  organic compounds.

• In the 1950s, various experiments were performed
  and showed that if the amino acids are heated
  without oxygen, they link and form complex
  molecules called proteins.

• A similar process produces ATP and nucleic acids
  from small molecules.

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Section 14.2 Summary pages 380-385
The formation of protocells

• The work of American biochemist Sidney Fox in
  1992 showed how the first cells may have occurred.

• Fox produced protocells by heating solutions of
  amino acids.

• A protocell is a large, ordered structure,
  enclosed by a membrane, that carries out some
  life activities, such as growth and division.

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Section 14.2 Summary pages 380-385
The Evolution of Cells

• Fossils indicate that by about 3.4 billion years
  ago, photosynthetic prokaryotic cells existed on
  Earth.

• But these were probably not the earliest cells.

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Section 14.2 Summary pages 380-385
The first true cells

• The first forms of life may have been prokaryotic
  forms that evolved from a protocell.

• Because Earths atmosphere lacked oxygen,
  scientists have proposed that these organisms
  were most likely anaerobic.

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Section 14.2 Summary pages 380-385
The first true cells

• For food, the first prokaryotes probably used
  some of the organic molecules that were abundant
  in Earths early oceans.

• Over time, these heterotrophs would have used up
  the food supply.

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Section 14.2 Summary pages 380-385
The first true cells

• However, organisms that could make food had
  probably evolved by the time the food was gone.

• These first autotrophs were probably similar to
  present-day archaebacteria.

84

The first true cells

• Archaebacteria (ar kee bac TEER ee uh) are
  prokaryotic and live in harsh environments, such
  as deep-sea vents and hot springs.

Section 14.2 Summary pages 380-385
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Section 14.2 Summary pages 380-385
The first true cells

• The earliest autotrophs probably made glucose by
  chemosynthesis rather than by photosynthesis.

• In chemosynthesis, autotrophs release the energy
  of inorganic compounds, such as sulfur compounds,
  in their environment to make their food.

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Section 14.2 Summary pages 380-385
Photosynthesizing prokaryotes

• Photosynthesizing prokaryotes might have been the
  next type of organism to evolve.

• As the first photosynthetic organisms increased
  in number, the concentration of oxygen in Earths
  atmosphere began to increase.

• Organisms that could respire aerobically would
  have evolved and thrived.

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Section 14.2 Summary pages 380-385
Photosynthesizing prokaryotes

• The presence of oxygen in Earths atmosphere
  probably affected life on Earth in another
  important way.

• The suns rays would have converted much of the
  oxygen into ozone molecules that would then have
  formed a layer that contained more ozone than the
  rest of the atmosphere.

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Section 14.2 Summary pages 380-385
The endosymbiont theory

• Complex eukaryotic cells probably evolved from
  prokaryotic cells.

• The endosymbiont theory,proposed by American
  biologist Lynn Margulis in the early 1960s,
  explains how eukaryotic cells may have arisen.

• The endosymbiont theory proposes that eukaryotes
  evolved through a symbiotic relationship between
  ancient prokaryotes.

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Section 14.2 Summary pages 380-385
The endosymbiont theory
A prokaryote ingested some aerobic bacteria. The
aerobes were protected and produced energy for
the prokaryote.
Some primitive prokaryotes also ingested
cyanobacteria, which contain photosynthetic
pigments.
Over a long time, the aerobes become
mitochondria, no longer able to live on their own.
The cyanobacteria become chloroplasts, no longer
able to live on their own.
Chloroplasts
Cyanobacteria
Mitochondria
Aerobic bacteria
Plant cell
Prokaryote
Animal Cell
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Section 14.2 Summary pages 380-385
The endosymbiont theory

• New evidence from scientific research supports
  this theory and has shown that chloroplasts and
  mitochondria have their own ribosomes that are
  similar to the ribosomes in prokaryotes.

• In addition, both chloroplasts and mitochondria
  reproduce independently of the cells that contain
  them.

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Section 14.2 Summary pages 380-385
The endosymbiont theory

• The fact that some modern prokaryotes live in
  close association with eukaryotes also supports
  the theory.

92
Section 2 Check
Question 1
Why did some scientists still believe in
spontaneous generation after Francesco Redis
experiments?
Answer
Although Redi disproved the spontaneous
generation of large organisms, many scientists
still believed microorganisms were so numerous
and widespread that they must arise spontaneously
from the air.
IN 2.1
93
Section 2 Check
Question 2
What is the difference between biogenesis and
spontaneous generation?
Answer
Spontaneous generation is the idea that life can
come from nonliving material. Biogenesis is the
idea that living organisms can come only from
other living organisms.
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Section 2 Check
Question 3
What two molecular developments must have
preceded the appearance life on Earth?
Answer
The formation of simple organic molecules, and
the organization of simple organic molecules into
complex organic molecules like proteins,
carbohydrates and nucleic acids that are
essential to life.
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Section 2 Check
Question 4
Who provided evidence to support Oparins
hypothesis that life began in the oceans on early
Earth?
A. Sidney Fox
B. Louis Pasteur
C. Francesco Redi
D. Stanley Miller and Harold Urey
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Section 2 Check
The answer is D, Stanley Miller and Harold Urey.
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Chapter Summary 14.1
The Record of Life

• Fossils provide a record of life on Earth.
  Fossils come in many forms, such as a leaf
  imprint, a worm burrow, or a bone.

• By studying fossils, scientists learn about the
  diversity of life and about the behavior of
  ancient organisms.

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Chapter Summary 14.1
The Record of Life

• Fossils can provide information on ancient
  environments. For example, fossils can help to
  predict whether an area had been a river
  environment, terrestrial environment, or a marine
  environment. In addition, fossils may provide
  information on ancient climates.

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Chapter Summary 14.1
The Record of Life

• Earths history is divided into the geologic time
  scale, based on evidence in rocks and fossils.

• The four major divisions in the geologic time
  scale are the Precambrian, Paleozoic Era,
  Mesozoic Era, and Cenozoic Era. The eras are
  further divided into periods.

100
Chapter Summary 14.2
The Origin of Life

• Francesco Redi and Louis Pasteur designed
  controlled experiments to disprove spontaneous
  generation. Their experiments and others like
  them convinced scientists to accept biogenesis.

• Small organic molecules might have formed from
  substances present in Earths early atmosphere
  and oceans. Small organic molecules can form
  complex organic molecules.

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Chapter Summary 14.2
The Origin of Life

• The earliest organisms were probably anaerobic,
  heterotrophic prokaryotes. Over time,
  chemosynthetic prokaryotes evolved and then
  photosynthetic prokaryotes that produced oxygen
  evolved, changing the atmosphere and triggering
  the evolution of aerobic cells and eukaryotes.

102
Chapter Assessment
Question 1
Is metamorphic rock a good source of fossils?
Answer
No, the conditions under which metamorphic rocks
form often destroy any fossils contained in the
original sedimentary rock.
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Chapter Assessment
Question 2
Why do scientists use relative dating techniques?
Answer
Relative dating allows scientists to compare the
age and order of appearance of a fossil relative
to those of the fossils appearing in the
sedimentary layers above or below it.
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Chapter Assessment
Question 3
Why do organisms that die on the surface of the
ground rarely become fossils?
Answer
Bacteria and fungi immediately decompose
organisms exposed to the air.
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105
Chapter Assessment
Question 4
Why are dinosaur exhibits in museums rarely
composed of real bones?
Answer
Minerals from sediments that covered dead
dinosaurs seeped into the dinosaurs body and
eventually replaced all the bodys bone material.
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Chapter Assessment
Question 5
Scientists use the carbon-14 isotope to date
fossils that are _______ years old.
A. less than 70 000
B. more than one million
C. 25 000
D. more than five million
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Chapter Assessment
The answer is A, less than 70 000.
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Chapter Assessment
Question 6
About how many years ago do fossils indicate that
photosynthetic prokaryotic cells existed on Earth?
A. 5.4 billion years
B. 3.4 billion years
C. 1.8 billion years
D. 543 million years
The answer is B, 3.4 billion years.
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Chapter Assessment
Question 7
Which forms of life developed earlier, anaerobic
single-celled organisms or aerobic single-celled
organisms, and why?
Answer
The answer is anaerobic single-celled organisms.
Anaerobic single-celled organisms developed at a
time when Earths atmosphere lacked oxygen.
Aerobic organisms, which require oxygen to
survive, developed later, when Earths atmosphere
contained a supply of oxygen.
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Chapter Assessment
Question 8
Why are archaebacteria able to survive in harsh
environments where most other organisms cannot?
Answer
Archaebacteria can release the energy of
inorganic compounds in their environment to make
their food rather than rely upon other organisms
for their food.
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Chapter Assessment
Question 9
What was the importance of Earths ozone layer to
the development of early organisms?
Answer
The ozone layer shielded early organisms from the
harmful effects of ultraviolet radiation and
enabled the evolution of more complex organisms.
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Chapter Assessment
Question 10
In Miller and Ureys laboratory experiment to
simulate the atmospheric conditions of early
Earth, what atmospheric condition did the
condenser simulate?
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Chapter Assessment
The condenser simulated rain in the atmosphere
that washed organic molecules into the ocean.
Entry for hydrogen, methane, and ammonia gases
Electrode
High voltage source
Condenser for cooling
Boiling water
Solution of organic compounds
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Chapter Assessment
Photo Credits

• Corbis
• Alton Biggs

115
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End of Chapter 14 Show