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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

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


Table of contents pages iv v1

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


Table of contents pages iv v2

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 Life’s Diversity


Table of contents pages iv v3

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

Table of Contents – pages iv-v


Table of contents pages iv v4

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


Table of contents pages iv v5

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


Unit overview pages 366 367

Unit Overview – pages 366-367

Changes Through Time

The History of Life

The Theory of Evolution

Primate Evolution

Organizing Life’s Diversity


Chapter contents page ix

Chapter Contents – page ix

Chapter 14The History of Life

14.1:The Record of Life

14.1:Section Check

14.2:The Origin of Life

14.2:Section Check

Chapter 14Summary

Chapter 14Assessment


Chapter intro page 368

Chapter Intro-page 368

What You’ll Learn

You will examine how rocks and fossils provide evidence of changes in Earth’s 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.


14 1 section objectives page 369

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.


Section 14 1 summary pages 369 379

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.


Section 14 1 summary pages 369 3791

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 Earth’s hot interior. These gases helped form Earth’s early atmosphere.


Section 14 1 summary pages 369 3792

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 lightning—enough rain to fill depressions that became Earth’s oceans.


Section 14 1 summary pages 369 3793

Section 14.1 Summary – pages 369-379

History in Rocks

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

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


Section 14 1 summary pages 369 3794

Section 14.1 Summary – pages 369-379

Fossils-Clues to the past

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

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


Section 14 1 summary pages 369 3795

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 Earth’s 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.


Section 14 1 summary pages 369 3796

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.


Section 14 1 summary pages 369 3797

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.


Section 14 1 summary pages 369 3798

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.


Section 14 1 summary pages 369 3799

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.


Section 14 1 summary pages 369 37910

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.


Section 14 1 summary pages 369 37911

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 body’s bone material.


Section 14 1 summary pages 369 37912

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.


Section 14 1 summary pages 369 37913

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.


Section 14 1 summary pages 369 37914

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.


Section 14 1 summary pages 369 37915

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.


Section 14 1 summary pages 369 37916

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.


Section 14 1 summary pages 369 37917

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.


Section 14 1 summary pages 369 37918

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.


Section 14 1 summary pages 369 37919

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 rock’s age.

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


Section 14 1 summary pages 369 37920

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 Earth’s history.

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


Section 14 1 summary pages 369 37921

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.


Section 14 1 summary pages 369 37922

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.


Section 14 1 summary pages 369 37923

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.


Section 14 1 summary pages 369 37924

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.


Section 14 1 summary pages 369 37925

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.


Section 14 1 summary pages 369 37926

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.


Section 14 1 summary pages 369 37927

Section 14.1 Summary – pages 369-379

Life during the Precambrian

  • The Precambrian accounts for about 87 percent of Earth’s history.

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


Section 14 1 summary pages 369 37928

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

Eukaryotes

Life evolves

Major Events

Period Era

Precambrian

4000

3500

1800

Million Years Ago


Section 14 1 summary pages 369 37929

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.


Section 14 1 summary pages 369 37930

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.


Section 14 1 summary pages 369 37931

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 Earth’s 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.


Section 14 1 summary pages 369 37932

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

Devonian

Ordovician

Silurian

Paleozoic Era

543

491

443

417

354

323

290

Million Years Ago


Section 14 1 summary pages 369 37933

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 Earth’s marine species and 70 percent of the land species disappeared at this time.


Section 14 1 summary pages 369 37934

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.


Section 14 1 summary pages 369 37935

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 mammals

First dinosaurs

First birds

Period

Triassic

Jurassic

Cretaceous

Era

Mesozoic Era

248

144

206

Million Years Ago


Section 14 1 summary pages 369 37936

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 mammals

First dinosaurs

First birds

Period

Triassic

Jurassic

Cretaceous

Era

Mesozoic Era

248

144

206

Million Years Ago


Section 14 1 summary pages 369 37937

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.


Section 14 1 summary pages 369 37938

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.


Section 14 1 summary pages 369 37939

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.


Section 14 1 summary pages 369 37940

Section 14.1 Summary – pages 369-379

Changes during the Mesozoic

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


Section 14 1 summary pages 369 37941

Section 14.1 Summary – pages 369-379

Changes during the Mesozoic

Click image to view movie.


Section 14 1 summary pages 369 37942

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.


Section 14 1 summary pages 369 37943

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, Earth’s 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.


Section 14 1 summary pages 369 37944

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.


Section 14 1 summary pages 369 37945

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

1.8

65

Million Years Ago


Section 1 check

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


Section 1 check1

Section 1 Check

The answer is D, the organisms that lived during that time interval.


Section 1 check2

Section 1 Check

Question 2

How can scientists determine when a mass extinction occurred in Earth’s history?

Answer

The fossils from a large percentage of species disappear from the fossil record almost at once.


Section 1 check3

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


Section 1 check4

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.


Section 1 check5

Section 1 Check

Question 4

Given that volcanoes have erupted since Earth’s 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.


Section 1 check6

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.


14 2 section objectives page 380

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.


Section 14 2 summary pages 380 385

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 generation—the idea that nonliving material can produce life.


Section 14 2 summary pages 380 3851

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 time—the idea that decaying meat produced maggots, which are immature flies.


Section 14 2 summary pages 380 3852

Section 14.2 Summary – pages 380-385

Spontaneous generation is disproved

  • Redi’s 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


Section 14 2 summary pages 380 3853

Section 14.2 Summary – pages 380-385

Spontaneous generation is disproved

  • However, during Redi’s time, scientists began to use the latest tool in biology—the 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.


Section 14 2 summary pages 380 3854

Section 14.2 Summary – pages 380-385

Pasteur’s 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.


Section 14 2 summary pages 380 3855

Section 14.2 Summary – pages 380-385

Pasteur’s experiments

The flask’s S-shaped neck allowed air to enter, but prevented microorganisms from entering the flask.

Each of Pasteur’s 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.


Section 14 2 summary pages 380 3856

Section 14.2 Summary – pages 380-385

Pasteur’s experiments

  • Pasteur’s 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.


Section 14 2 summary pages 380 3857

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.


Section 14 2 summary pages 380 3858

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.


Section 14 2 summary pages 380 3859

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 Earth’s heat triggered chemical reactions to produce small organic molecules from the substances present in the atmosphere.


Section 14 2 summary pages 380 38510

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 Oparin’s hypothesis by simulating the conditions of early Earth in the laboratory.


Section 14 2 summary pages 380 38511

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


Section 14 2 summary pages 380 38512

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.


Section 14 2 summary pages 380 38513

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.


Section 14 2 summary pages 380 38514

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.


Section 14 2 summary pages 380 38515

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 Earth’s atmosphere lacked oxygen, scientists have proposed that these organisms were most likely anaerobic.


Section 14 2 summary pages 380 38516

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 Earth’s early oceans.

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


Section 14 2 summary pages 380 38517

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.


Table of contents pages iv v

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


Section 14 2 summary pages 380 38518

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.


Section 14 2 summary pages 380 38519

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 Earth’s atmosphere began to increase.

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


Section 14 2 summary pages 380 38520

Section 14.2 Summary – pages 380-385

Photosynthesizing prokaryotes

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

  • The sun’s 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.


Section 14 2 summary pages 380 38521

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.


Section 14 2 summary pages 380 38522

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


Section 14 2 summary pages 380 38523

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.


Section 14 2 summary pages 380 38524

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.


Section 2 check

Section 2 Check

Question 1

Why did some scientists still believe in spontaneous generation after Francesco Redi’s 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.


Section 2 check1

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.


Section 2 check2

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.


Section 2 check3

Section 2 Check

Question 4

Who provided evidence to support Oparin’s 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


Section 2 check4

Section 2 Check

The answer is D, Stanley Miller and Harold Urey.


Chapter summary 14 1

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.


Chapter summary 14 11

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.


Chapter summary 14 12

Chapter Summary – 14.1

The Record of Life

  • Earth’s 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.


Chapter summary 14 2

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 Earth’s early atmosphere and oceans. Small organic molecules can form complex organic molecules.


Chapter summary 14 21

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.


Chapter assessment

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.


Chapter assessment1

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.


Chapter assessment2

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.


Chapter assessment3

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 dinosaur’s body and eventually replaced all the body’s bone material.


Chapter assessment4

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


Chapter assessment5

Chapter Assessment

The answer is A, less than 70 000.


Chapter assessment6

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.


Chapter assessment7

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 Earth’s atmosphere lacked oxygen. Aerobic organisms, which require oxygen to survive, developed later, when Earth’s atmosphere contained a supply of oxygen.


Chapter assessment8

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.


Chapter assessment9

Chapter Assessment

Question 9

What was the importance of Earth’s 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.


Chapter assessment10

Chapter Assessment

Question 10

In Miller and Urey’s laboratory experiment to simulate the atmospheric conditions of early Earth, what atmospheric condition did the condenser simulate?


Chapter assessment11

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


Chapter assessment12

Photo Credits

Chapter Assessment

Corbis

Alton Biggs


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