Biology Chapter 17

Evolution:

The History of Life

More than ______ of all species that have ever lived on Earth have become extinct.

99.9%

17-1 The Fossil Record

I. Fossils and Ancient Life

A. _______________ are scientists who study fossils.

B. The fossil record _________ evidence about the history of life on Earth. It also shows how different

__________ _____________, including species, have changed over time.

Paleontologists

provides

groups oforganisms

II. How Fossils Form A. For a fossil to form, either the _________

___________ or some trace of its presence must be preserved.

1. A precise _________________ must be present to form a fossil.

2. The fossil record provides ____________ ____________ about the history of life.

remains ofthe organism

set of conditions

incompleteinformation

B. Most fossils are formed in ___________ _______.

1. Sedimentary rock forms from the

_________________________________

2. These particles are carried by _________ ___________ into lakes or seas, where they eventually settle to the bottom.

sedimentary

rock.

erosion of rock into sand, silt, and clay.

streamsand rivers

3. As layers of sediment build up over time, ________________________________

_______ and become buried.

4. If conditions are right, the ________ may be kept intact and free from decay.

5. The sediment gradually _____________

_______

dead organisms may also sink to the bottom

remains

compresses into

rock.

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

Figure 17-2 Formation of a Fossil

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III. Interpreting Fossil Evidence

A. Paleontologists determine the ________ _______ using two techniques:

1. Relative Dating

a. The age of the fossil is determined by ______________________ with that of fossils in other layers of rock.

b. Rock layers __________________ are generally ________ than those below it.

age of fossils

comparing its placement

nearer to the surfaceyounger

Relative Dating

c. Does not determine the ___________ of the rocks or the fossils.

d. Index fossils are used to ____________ ___________________. These

fossils must be easily recognized and must have existed for a short period of time.

actual age

compare the relative age of fossils

2. Radioactive Datinga. Based on the ___________________

___________________.b. Radioactive elements decay, ________

______, at a steady rate which is measured in a unit called half-life.

c. Half-life: the length of time required for __________________________ in

a sample to decay.

radioactive decay ofelements in the rocks

or breakdown

half of the radioactive atoms

d. Different radioactive elements have different half-lives and therefore provide ______________ that “tick” at ______________.

Example:

Carbon-14: half-life of about ______ ________

Potassium-40 : half-life of about ______ ___________

natural clocksdifferent rates

5,730years

1.26

billion years

e. Carbon-14 is _________ by living things while ______________. After an organism dies, the __________ in its body begins to decay to form _________

___, which escapes into the air.

f. Carbon-14 has a relatively ____________,

it is useful only for dating fossils younger than about ____________.

taken upthey are alive

Carbon-14 nitrogen-

14

short half-life

60,000 years

Carbon-14

Radioactive Decay

B. Most fossils are __________. Paleontologists must reconstruct an extinct species from a few fossil bits---remains of bone, a shell, leaves, or pollen.

not intact

http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html

Relative Dating

Can determine

Is performed by

Drawbacks

Absolute Dating

Comparing Relative and Absolute Dating of Fossils

Section 17-1

Compare/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 non-radioactive 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

IV. Geologic Time Scale

A. Scientists first developed the _________ _____________ by studying rock layers and index fossils worldwide. As geologists studied the fossil record, they found _______ ________ in the fossil animals and plants

_________________________. These times were used to mark the segments.

geologictime scale

majorchanges

at specific layers in the rock

1. Eras: There are __ eras between the

___________________________.

a. ______________

b. ______________ (Age of Dinosaurs)

c. ______________ (Age of Mammals)

2. Periods: Eras are subdivided into ______.

3Precambrian and the present

Paleozoic Era

Mesozoic EraCenozoic Era

periods

Continental Drift

Plate Boundaries

San Andreas Fault

17-2 Earth’s Early History and 17-3 Evolution of Multicellular Life

4.6 bya.... *___________________*many sources of energy: volcanic

activity, lightening, meteorites*______________ in atmosphere:

water vapor (H20), nitrogen (N2), and carbon dioxide (CO2), with only small amounts of hydrogen (H2) and carbon monoxide. The primitive atmosphere had little, if any, free _______.

no life forms present

poisonous gases

oxygen

* intense UV (ultraviolet radiation) from sun

* In the presence of so much available energy, the primitive gases may have reacted with one another and produced small organic compounds, such as nucleotides and amino acids.

3.5 bya… *geological disturbances have calmed

*____________________________

_____________ (much like the bacteria of today and well adapted)

bacteria evolve and inhabit mostenvironments

2.2 bya.... *____________________ and form mats in shallow seas. ________ ___________ to produce oxygen (02) via ______________

cyanobacteria evolveFirst

organisms

photosynthesis

1 bya.... *algae and other water-borne photosynthetic organisms abound

in the seas

* __________________ in the seas with many

______________________ like sponges, jellyfish and worms.

Green Algae Red AlgaeBrown Algae

animal life aboundsmulticellular organisms

A SPECIAL NOTE ON THE EVOLUTION OF OUR ATMOSPHERE:

1. __________________ begins in the seas2. ____________________________ (electrical

storms split atmospheric water molecules releasing a single oxygen)

3. _______________________________ - (here single oxygen and regular oxygen unite to form O3 or ozone)

4. ___________________ stratosphere - ________ _____ most of the ________________. Life on land can now thrive under this protective ______ which begins 12-15 miles above the earth’s surface.

Oxygen saturationOxygen moves into atmosphere

Oxygen reaches upper atmosphere

Ozone layer forms in filteringout harmful UV rays

shield

Paleozoic Era

550 mya.... “____________________” - the Cambrian Period records _____________ _______ of life in evolution’s history. Nearly all of the animal groups known today as well as a strange collection of animals that cannot be assigned to any living group of today appeared in a period of about 10 million years. This evidence is not based upon fossils.

the Cambrian Explosion an unmatched

burst

550 mya.... “the Cambrian Explosion”Scientists are ________________________

________________ of evolution found in the genes drawn from the living species of 16 animal groups. This has allowed scientists to estimate when all animals last shared a common ancestor with other forms of life. Although controversial, this evidence without the fossil “backup” is widely accepted by many scientists in the field today. If this finding holds up, the animal kingdom had __________________ ___________to develop than the fossils reveal.

basing this new finding upon molecular evidence

hundreds of millions of years longer

410 mya..... the “______________”

Cartilaginous Fishes: Sharks, Skates and Rays

age of the fishes

Bony Fishes

360 mya...... ________________________ climb onto the land.

first land-based amphibians

Amphibian: Frog

• 300 mya......______________________--the earth is now a large vegetated landmass with open plains, swamps and primitive trees. ____________ flourished in a tropical climate. Invertebrates flourished in the ocean. From these forests and swamps, of the so called “_____________” period, came the organic materials that ultimately formed our___________________.

primitive reptiles appear

Large insects

Carboniferous

fossil fuels of today

Coal Forest “Carboniferous Period” (300 mya)

• 240 mya..._______________________ __________________________________ over a 100,000 year period. This was possibly due to a meteor impact. This occurred at the end of the_____________.

a period of mass extinctions where perhaps 95% of all life perished

Paleozoic Era

Mesozoic Era: Began 245 myaLasted 180 million years

Reptiles: Lay eggs on land

Bull Snake

• 205 mya..... beginning of the domination of ___________ for 120 mya

• 138 mya..... ____________________ occur on land and the beginnings of tropical rain forests in some areas. The flowering plants spread and ultimately dominated the landscape through a period of 65 million years.

dinosaurs

first flowering plants

• 65 mya.....

Meteorite activity is one explanation for this extinction. This occurred at the end of the_______________.

an era of mass extinction that ended the dinosaurs as well as 75% of all plant and animal life.

Mesozoic Era

Cenozoic Era: Mammals spread out and began to dominate the landscape.

Mammal: Chimpanzee

• 100,000-200,00 years ago.......

__________________ Homo sapiens date to about this time. Homo sapiens means “_________ __________” and modern humans are classified in this species.

the earliest fossils of intelligent

human

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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17-4 overview

Study guide 17-1

1. Paleontologists2. It is information about past life that is based on fossils.3. It provides evidence about the history of life on Earth and how different groups of

organisms, including species, have changed over time.4. Extinct5. False6. B, D7. Sediments settle to the bottom of lakes and seas ad bury dead organisms. The weight of

upper layers of sediment compresses lower layers into rock and turns the dead organisms into fossils.

8. a) Relative dating b) Radioactive dating9. A, B, D10. False11. True12. Half-life13. Radioactive dating14. They measure the amount of remaining radioactive isotopes it contains. The smaller the

amount, the older the sample.15. False16. Cenozoic, Mesozoic, Precambrian time, Tertiary, Jurassic, Carboniferous, Silurian,

Cambrian17. C18. A, B19. Eras and periods20. Mesozoic Era21. Cenozoic Era

Study guide 17-21. a) Hydrogen Cyanide b) Carbon Dioxide c) Carbon Monoxide d) Nitrogen e)

Hydrogen Sulfide f) Water2. False3. Spark simulating lightning storms4. A, B5. They are tiny bubbles, formed of large organic molecules, that have some

characteristics of living cells.6. False7. Experiments show that small sequences of RNA could have formed and replicated on

their own in the conditions present on early Earth.8. DNA is a more stable information-storing molecule than RNA.9. Microfossils10. A11. They produced oxygen, which first removed iron from the oceans and then

accumulated in the atmosphere.12. True13. True14. The first step was the evolution of internal cell membranes.15. It proposes that eukaryotic cells arose from living communities formed by several

organisms.16. A,C,D17. Sexual reproduction shuffles and reshuffles genes in each generation. This increase

in genetic variation greatly increases the chances of evolutionary change due to natural selection.

18. False

Study Guide 17-31. True2. A,B,C3. The animals were al soft-bodied4. Cambrian5. False6. A,B,D7. B8. C9. A10. Devonian11. Vast swampy forests of giant ferns and other plants that grew during that time formed thick

deposits of sediment that changed into coal over million of years.12. Mass extinction13. False14. Triassic, Jurassic, Cretaceous15. Reptiles16. Triassic17. True18. True19. Reptiles20. Their seeds are enclosed in a fruit, which protects the seed and aids in dispersing it to new

locations.21. More than half of all plant and animals groups were wiped out, including all of the dinosaurs.22. True23. Mammals24. They were generally warm and mild.25. First it cooled, causing a series of ice ages. The, it began to warm again.26. False

Study guide17-41. Macroevolution2. a.)extinction b.)Adaptive radiation c.)Convergent evolution d.)Coevolution

e.)Punctuated equilibrium f.)changes in developmental genes3. Possible causes include a huge asteroid striking Earth, many large volcanoes

erupting, continents changing position, and sea levels changing.4. The disappearance of so many species left habitats open. Often, the result was

burst of evolution that produced many new species.5. Adaptive evolution6. The disappearance of the dinosaurs led to the adaptive radiation of mammals.7. Convergent evolution8. B9. Coevolution10. Plats have evolved poisons prevent insects from feeding on them. Insects, in turn,

have evolved ways of inactivating or eliminating the poisons.11. gradualism12. it may occur when a small population becomes isolated or a small group migrates

to a new environment. It may also occur following a mass extinction.13. Punctuated equilibrium14. True15. Homologous hox genes establish body plans in animals that have not shared a

common ancestor in hundreds of millions of years. In addition, major evolutionary changes may be based on hox genes.

16. True

Study guide Vocabulary review

1. C2. D3. A4. C5. B6. In coevolution, two species evolve in response to changes in

each other over time.7. Convergent evolution refers to the process by which unrelated

organisms come to resemble one another as the evolve similar adaptations to similar environments.

8. Mass extinction is the occurrence of many extinctions around the same time.

9. Punctuated equilibrium is a pattern of macroevolution in which long, stable periods are interrupted by brief periods of rapid change.

10. In adaptive radiation, a single species, or a small group of species, evolves into diverse forms that live in different ways.