17–1The Fossil Record A. Fossils and Ancient Life The fossil record provides evidence about the history of life on earth. It also shows how different.

17–1 The Fossil Record

A. Fossils and Ancient Life− The fossil record provides evidence about

the history of life on earth. It also shows how different groups of organisms have changed over time


B. How Fossils Form− Most fossils form in sedimentary rock. It is

formed when exposure to rain, heat, wind and cold breaks down clay

− As layers of sediment build up over time, dead organisms may also sink to the bottom and become buried

− Conditions are right, the remains may be kept intact


C. Interpreting Fossil Evidence1. Relative Dating- the age of a fossil is

determined by comparing its placement with that of fossils in other layers of rock (estimate age of fossils)

2. Radioactive Dating- scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains


D. Geologic Time Scale

1. Eras

2. Periods

Relative Dating

Can determine

Is performed by

Drawbacks

Absolute Dating

Comparing Relative and Absolute Dating of Fossils

Section 17-1Compare/Contrast Table

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Imprecision and limitations of age data

Difficulty of radio assay laboratory methods

Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock

Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen

Age of fossil with respect to another rock or fossil (that is, older or younger)

Age of a fossil in years

Figure 17-2 Formation of a Fossil

Water carries small rock particles to lakes and seas.

Dead organisms are buried by layers of sediment, which forms new rock.

The preserved remains may later be discovered and studied.

Section 17-1

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Figure 17-5 Geologic Time Scale

Era Period Time

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

(millions of years ago)Era Period Time

(millions of years ago)Era Period Time(millions of

years ago)

290 – 245

363–290

410–363

440–410

505–440

544–505

1.8–present

65–1.8

145–65

208–145

245–208

Quarternary

Tertiary

Cretaceous

Jurassic

Triassic

Vendian 650–544

Section 17-1

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Era Period Time

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian



years ago)

290 – 245

363–290

410–363

440–410

505–440

544–505

1.8–present

65–1.8

145–65

208–145

245–208

Quarternary

Tertiary

Cretaceous

Jurassic

Triassic

Vendian 650–544

Section 17-1



Era Period Time

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian



years ago)

290 – 245

363–290

410–363

440–410

505–440

544–505

1.8–present

65–1.8

145–65

208–145

245–208

Quarternary

Tertiary

Cretaceous

Jurassic

Triassic

Vendian 650–544

Section 17-1Figure 17-5 Geologic Time Scale

17–2 Earth’s Early History

A. Formation of Earth

−Earth’s early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water


B.The First Organic Molecules

− Organic molecules would have been able to be constructed but the oxygen in atmosphere was to reactive and would destroy any organic molecules that formed


C. How Did Life Begin?

1. Formation of Microspheres- protection that allowed for the growth of organic molecules

2. Evolution of RNA and DNA- still unanswered but scientists are searching

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D.Free Oxygen

− The rise of oxygen in the atmosphere drove some life forms to extinction, while other life forms evolved new, more efficient metabolic pathways that used oxygen for respiration


E.Origin of Eukaryotic Cells

− The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms

Aerobic bacteria

Ancient Prokaryotes

Ancient Anaerobic Prokaryote

Primitive Aerobic Eukaryote

Primitive Photosynthetic Eukaryote

Chloroplast

Photosynthetic bacteria

Nuclear envelope evolving Mitochondrion

Plants and plantlike protists

Animals, fungi, and non-plantlike protists

Figure 17-12 Endosymbiotic Theory

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F. Sexual Reproduction and Multicellularity

− A few hundred million years after the evolution of sexual reproduction, evolving life forms crossed to developing multicellular organisms from single celled (unicellular) organisms

17–3 Evolution of Multicellular Life

A. Precambrian Time- life existed only in the sea

B. Paleozoic Era- rich with evidence of many types of marine life

C. Mesozoic Era- increasing dominance of dinosaurs, appearance of flowering plants

D. Cenozoic Era- mammals evolved adaptations that allowed them to live in various environments, on land, water and air

Section 17-3Geologic Time Scale with Key Events

Glaciations; mammals increased; humans

Mammals diversified; grasses

Aquatic reptiles diversified; flowering plants; mass extinction

Dinosaurs diversified; birds

Dinosaurs; small mammals; cone-bearing plants

Reptiles diversified; seed plants; mass extinction

Reptiles; winged insects diversified; coal swamps

Fishes diversified; land vertebrates (primitive amphibians)

Land plants; land animals (arthropods)

Aquatic arthropods; mollusks; vertebrates (jawless fishes)

Marine invertebrates diversified; most animal phyla evolvedAnaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life

Cenozoic

Mesozoic

Paleozoic

PrecambrianTime

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

1.8–present

65–1.8

145–65

208–145

245–208

290–245

363–290

410–363

440–410

505–440

544–505

650–544

Key EventsEra Period Time(millions of years ago)

17–4 Patterns of Evolution

A. Mass Extinctions- dinosaurs

B. Adaptive Radiation- species evolved into several different forms that live in different ways

C. Convergent Evolution- unrelated organisms come to resemble one another

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D. Coevolution- process by which two species evolve in response to changes in each other over time

E. Punctuated Equilibrium- patterns of long, stable periods interrupted by brief periods of more rapid change

Gradualism- patterns of slow, gradual change

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F. Developmental Genes and Body Plans- changes in developmental genes, revealing major news about evolution of life

Flowchart

that are

can undergo can undergo can undergo can undergo can undergo

in underunderform inin

Species

Unrelated Related

Inter-relationshiops

Similar environments

Intense environmental

pressure

Small populations

Different environments

Coevolution Convergent evolution

ExtinctionPunctuated equilibrium

Adaptive radiation

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•A Trip Around the World

•While on his voyage around the world aboard the H.M.S. Beagle, Charles Darwin spent about one month observing life on the Galápagos Islands. There, he encountered some unique animals, such as finches and tortoises.

Section 15-1

• 1. On a sheet of paper, list five animals that you have encountered in the past two days.

• 2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15–3 and 15–4 in your textbook.)

• 3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands.

A. Voyage of the BeagleB. Darwin’s Observations

1. Patterns of Diversity2. Living Organisms

and Fossils3. The Galápagos

IslandsC. The Journey Home

Section 15-1•15–1 The Puzzle of Life’s Diversity

Giant Tortoises of the Galápagos Islands

Pinta IslandIntermediate shell

Pinta IslandIntermediate shell

Hood IslandSaddle-backed shell

Figure 15–1 Darwin’s Voyage

My, How You’ve Changed!

• Prior to the 1800s, life scientists knew that living things changed over generations. They just didn’t know how these changes were brought about.

1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.

2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument.

3. Which of the items in your lists do you think you might pass on to your children? Explain your answer

15–2 Ideas That Shaped Darwin’s Thinking

A. An Ancient, Changing Earth1. Hutton’s Theory of Geological Change

2. Lyell’s Principles of Geology

15–2 Ideas That Shaped Darwin’s Thinking

B.Lamarck’s Theory of Evolution

1. Tendency Toward Perfection2. Use and Disuse3. Inheritance of Acquired Traits4. Evaluating Lamarck’s Theory

C.Population Growth

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Hutton’s Theory of Geological Change

• In 1975, geologist James Hutton proposed that layers of rock form very slowly. Some rocks are moved up by forces beneath the Earth’s surface, others are buried. Resulting rocks, mountains, and valleys are then shaped by a variety of natural forces-including rain, heat and cold temperatures

Lyell’s Principles of Geology

• Lyell’s work explained how awesome geological features could be built up or torn down over long periods of time.

• His work influenced Darwin in two ways:

• If the earth could change overtime, might life change as well?

• He realized that it must have taken many, many years, earth must be very old

Movement of Earth’s Crust

Sedimentary rocks form in horizontal layers

When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.

As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

New sediment is then deposited above the exposed older rock surface.

Lamarck’s Theory of Evolution1. Tendency Toward Perfection

− He proposed that all organisms are continually changing and acquiring features that help them live more successfully in their environment

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2. Use and Disuse

− He proposed that organisms could alter the size or shape of particular organs by using their bodies in new ways.

− Conversely, if a winged animal did not use its wings (ex. of disuse) the wings would decrease in size over generations and finally disappear

3. Inheritance of Acquired Traits

• Lamarck thought that acquired characteristics could be inherited

• By this reasoning, if you spent much of your life lifting weights to build muscles, your children would inherit big muscles, too.

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4. Evaluating Lamarck’s Theory

− He was incorrect in many ways

− Lamarck, like Darwin, did not know how traits are inherited or that behavior has no effect on its inheritable characteristics

− One of first to develop scientific theory of evolution and realize that organisms are adapted to their environment

Figure 15–7 Lamarck’s Theory of Evolution

15–3 Darwin Presents His Case

A. Publication of On the Origin of Species– Darwin(1859)proposed a mechanism for

evolution called natural selection– Continuous for millions of years and

continues in all living things– Others strongly opposed


B. Natural Variation and Artificial Selection– Natural variation is the differences among

individuals of a species, is found in all types of organisms

– Artificial Selection occurs through a technique called selective breeding, that would determine which individuals to use for breeding based on the natural variation that was found

15–3 Darwin Presents His Case C.Evolution by Natural Selection

1. The Struggle for Existence- means that members of each species compete regularly to obtain food, living space, an other necessities of life


C. Evolution by Natural Selection2. Survival of the Fittest

− Fitness- the ability of an individual to survive and reproduce in its specific environment

− Adaptation- is any inherited characteristics that increase an organism’s chance of survival



− Individuals that are better suited to their environment-that is, with high levels of fitness-survive and reproduce most successfully



− Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in it’s environment


C. Evolution by Natural Selection

3. Descent With Modification

− Each living species has descended, with changes, from other species over time


D. Evidence of Evolution

1. The Fossil Record

− provided evidence that living things have been evolving for millions of years.

− Sometimes fossil records includes similar, intermediate forms of a group of organisms that together suggest gradual modification over time

includes

Evidence of Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil recordGeographic

distribution of living species

Homologous body structures

Similaritiesin early

development


2. Geographic Distribution of Living Species

− Animals living under similar ecological conditions, were exposed to similar pressures of natural selection

− Because of these similar selection pressures, different animals ended up evolving certain striking features in common

Figure 15–14Geographic Distribution of Living Species

Beaver MuskratBeaver andMuskratCoypu CapybaraCoypu andCapybara


3. Homologous Body Structures

− structures that have different mature forms and functions but develop from the same embryonic tissues

Figure 15–15 Homologous Body Structures

Turtle Alligator Bird Mammals

Typical primitive fish


4.Similarities in Early Development

− early stages, or embryos, of many animals with backbones are so similar that they can be hard to tell apart

E. Summary of Darwin’s Theory

− Organisms in nature differ, some variation is inherited

− Survival of the fittest

− Natural Selection

− Variation

1. Make a list of physical traits that you think are influenced by genes.Then, write next to each trait whether you have the trait or not(e.g., a widow’s peak) or whether there are many variations of thetrait (e.g., hair color).

2. Are most of the traits you listed clear-cut or are they mostly traitsthat have many variations? Which traits in your list are difficult tocategorize?

3. Compare your list with that of another student. Did he or she think of any traits that you missed? Why do you think some traits are clear-cut,while others are not?

16–1 Genes and VariationA. Darwin’s Ideas Revisited

− Without an understanding of heredity, Darwin was unable to explain two important factors. First, he did not know the source of the variation that was so central to his theory. Second, he could not explain how inheritable traits were passed from one generation to the next.

16–1 Genes and Variation

B. Gene Pools

− is the combined genetic information of all the members of a particular population

16–1 Genes and VariationC. Sources of Genetic Variation

− Mutations- is any change in a sequence of DNA

− Gene Shuffling- occurs during the production of gametes (23 chromosomes in sperm and 23 in egg=46 Zygote)

− Crossing over- exchange of genetic material between chromosomes

16–2 Evolution as Genetic Change

C. Genetic Drift

− In small, populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurrences of this type can cause an allele to become common in a population


D. Evolution Versus Genetic Equilibrium

1. Random Mating

− Ensures that each individual has an equal chance of passing on it’s alleles



2. Large Population

− Important in maintaining genetic equilibrium

− Genetic drift has less effect on large populations



3. No Movement Into or Out of the Population

− Keep gene pool together and separate of other populations



4. No Mutations



5. No Natural Selection

Sample of Original Population

Founding Population A

Sample of Original Population

Founding Population B

Founding Population B

Founding Population A

Sample of Original Population Descendants

• Country Cousin/City Cousin

• What happens when a population or group of living things is dividedinto two separate groups in two separate environments? To understand what goes on, think about someone who lives in another part of the United States or in another country.

• 1. Make a list of everyday things that this person encounters that you don’t. For example, does he or she eat different kinds of food? Does he or she live in a climate different from yours?

• 2. All humans are the same species. What might happen if groups of humans were separated for millions of years in very different environments, such as those you have just described?

16–3 The Process of SpeciationA. Isolating Mechanisms

− As new species evolve, populations become reproductively isolated from each other

1. Behavioral Isolation- two populations are capable of interbreeding, but differences in courtship rituals

2. Geographic Isolation- two populations are separated by geographic barriers such as rivers, mountains, or bodies of water

3. Temporal Isolation- two or more species reproduce at different times (orchid in the rainforest)

16–3 The Process of Speciation

B. Testing Natural Selection in Nature1. Variation- Grant’s concluded that there is

a great deal of variation of inheritable traits among the Galopagos finches

2. Natural Selection- when food for finches was scarce, individuals with the largest beaks were more likely to survive

3. Rapid Evolution- changes in beaks occurred over decades instead of thousands of years


C. Speciation of Darwin’s Finches

1. Founders Arrive

2. Separation of Populations

3. Changes in the Gene Pool

4. Reproductive Isolation

5. Ecological Competition

6. Continued Evolution



1. Founders Arrive

− Once they arrived on one of the island, they managed to survive and reproduce



2. Separation of Populations

− Species crossed islands



3. Changes in the Gene Pool

− Over time natural selection would have caused that population to evolve larger beaks, forming a separate population



4. Reproductive Isolation

− Gene pools of the two bird populations remain isolated from each other

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5. Ecological Competition

− Overtime, species evolve in a way that increases the differences between them



6. Continued Evolution

− Over many generations, it produced the 13 finch species found there today

results from

which include

produced by produced byproduced by

which result in

which result in

Reproductive Isolation

Isolating mechanisms

Behavioral isolation Temporal isolationGeographic isolation

Behavioral differences Different mating timesPhysical separation

Independentlyevolving populations

Formation ofnew species

The End

17–1The Fossil Record A. Fossils and Ancient Life The fossil record provides evidence about the history of life on earth. It also shows how different.

Documents

time slide

fossil water

water slide

geologic time scale

reference fossil

intact slide

fossil record b

specimen age of fossil